United States EPA~600/9-89-Q57
Environmental Protection
A9encv June 1989
Research and
Development
PROCEEDINGS OF THE
RADON DIAGNOSTICS WORKSHOP
APRIL 13-14, 1987
Prepared for
Office of Radiation Programs
Prepared by
Air and Energy Engineering Research
Laboratory
Research Triangle Park NC 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
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1. Environmental Health Effects Research
2. Environmental Protection Technology
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4. Environmental Monitoring
5. Socioeconomic Environmental Studies
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This report has been reviewed by the U.S. Environmental Protection Agency, and
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This document ia available to the public through the National Technical Information
Service, Springfield, Virginia 22161.
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Abstract
Diagnostic approaches offer improved evaluations of radon-related
indoor air quality problems. An informed solution involves knowledge of the
building, the building site and the interaction of radon sources with the
living space. The diagnostics are applicable in four phases of the
mitigation process. The first phase consists of diagnostics which assess
the radon problem. The second phase involves the pre-mitigation
diagnostics. From this phase of the diagnostics a suitable mitigation
approach must be chosen. Third are the important diagnostics that check the
performance of the radon mitigation solution. Finally, the fourth phase of
radon diagnostics determines if the radon problem has been solved and that
guideline radon concentrations have not been exceeded over the different
seasonal conditions experienced.
A consensus of current knowledge on important radon diagnostic
techniques and how they may be best applied are the result of a two-day
Radon Diagnostics Workshop sponsored by the U.S. EPA held at Princeton
University, April 13-14, 1987- That knowledge is summarized, placing the
various radon diagnostic techniques in perspective.
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TABLE OF CONTENTS
Page
Abstract ii
Preface iv
A. WORKSHOP SUMMARIES 1
I. RADON PROBLEM ASSESSMENT M. Mardis, Chairman 1
II. PRE-MITIGATION DIAGNOSTICS - L. M. Hubbard, Chairman 5
III. MITIGATION INSTALLATION DIAGNOSTICS M. Osborne, Chairman 10
IV. POST MITIGATION DIAGNOSTICS - B. Henschel, Chairman 14
B. WORKSHOP PRESENTATIONS 18
General Considerations Related to Radon Diagnostics 19
J. Tell Tappan
Use of Vehicle-Mounted Radiological Equipment in the Diagnosis of 28
Houses with Elevated Levels of Radon and its Short-Lived Progeny
C.S. Dudney, B.A. Berven, T.G. Matthews and A.R. Hawthorne
Soil Characterization for Radon Availability and Transport 35
C. Kuntz
Overview of Selecting Radon Mitigation Methods 43
T. Brennan
Interim Report on Diagnostic Procedures for Radon Control 56
B.H. Turk, J. Harrison, R.J. Prill and R.G. Sextro
Guaranteed Radon Remediation Through Simplified Diagnostics 72
D. Saum and M. Messing
Follow-up Diagnostics - How Well Does the Mitigation Work 77
and Does it Meet the Guidelines?
K.J. Gadsby, D.T. Harrje, L.M. Hubbard and C.A. Decker
C. WORKSHOP DISCUSSIONS - Phase I - pg 81, Phase II-pg 101, 80
Phase Ill-pg 109 & Phase IV-pg 118
D. ADDITIONAL MATERIAL - Supplemental Radon Diagnostics Infor- 125
Mation from the Piedmont Study plus diagnostic Master List
E. REFERENCES 151
F. ATTENDEES 161
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PREFACE
The scope and objectives of the Radon Diagnostics Workshop were to gain
an improved prospective, and to develop guidelines on the usefulness and
range of applicability of different diagnostic techniques. To categorize
state-of-the-art diagnostic methods, and to treat questions the diagnostic
methods seek to answer regarding radon emination, transport, entry and
indoor distribution, four phases of radon diagnostics were highlighted in
the Workshop. These phases are:
I. Radon Problem Assessment Diagnostics: radon source strength and
location, house characteristics, and house occupancy
characteristics.
II. Pre-Mitigation Diagnostics: selecting the best mitigation system
for the particular building taking into account radon "hotspots"
and other special conditions particularly as related to the house
substructure.
III. Mitigation Installation Diagnostics: used during installation of
mitigation systems to assure proper operation.
IV. Post Mitigation Diagnostics: assurance that the radon guidelines
have been met and that the mitigation system is adjusted properly.
The background of the attendees was varied, but much of their
experiences with radon has been a direct result of the U.S. EPA, DOE and
state programs attempting to understand and mitigate radon problems in
primarily residential buildings. Examples of that experience come from
states all over the U.S., as well as Canada.
A critical review of the effectiveness of current diagnostic procedures
was part of the Workshop agenda. Panel discussions focused upon the
various diagnostic methods with emphasis given to questions such as:
a) How good is the rationale for the diagnostic measurement?
b) How easy is the diagnostic procedure?
c) What resources and expenses are required to implement the
diagnostics?
d) What information can be obtained from using the diagnostics?
The format of the workshop proceedings begins with summaries of each
ofthe four phases of radon diagnostics. The summaries provide a quick
overview of the topics discussed and conclusions reached in the
discussions, and refer the reader to more detailed treatment of the
various topics in the text that follows. The Workshop Presentations are a
part of that text together with the Workshop Discussions.
IV
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The emphasis on diagnostics in radon troubled homes is a quest for
additional knowledge as to the severity of the problem, the approach that
may be used for solution of the problem and to evaluate the way the
solution is working out. It was clear in the Workshop discussions that
such diagnostics are absolutely necessary in some homes but many of the
procedures are not cost effective in the homes that are simpler to
mitigate. Anticipating possible radon problems at the house design phase
is likely to prove more cost effective than extensive soil probing to
quantify the radon problem potential for the individual building lot.
Measurements to determine radon levels for the majority of our homes are
generally recommended. In those areas of high incidence of homes with
radon levels greater than the EPA guidelines and/or regions where very
high house radon levels have been observed, every homeowner should check
their house for radon concentration levels.
Where radon problems exist it is important to evaluate exactly what
should be done. In homes with concrete basement floor slabs the
diagnostic approach receiving wide acceptance is to check for
communication under the slab. Subslab suction is commonly used to remove
the radon gas via a fan and piping that exhaust to the outside, but
diagnostics are necessary to make certain that suction extends over the
entire slab. That openings through slab or basement walls need only be a
few square centimeters, points out that just sealing the
basement/crawlspace may not be enough, and that active or passive radon
venting may be needed. A knowledge of how the house and its equipment
function with respect to providing the pressure differences that drive the
radon flow is necessary if the correct measures are to be taken.
Diagnostics after mitigation devices are in place are necessary to
insure that the job has been done correctly. An informed homeowner or
private testing agency is recommended for these checks so as to avoid the
conflict of interest of a mitigator justifying his solution has been
effective.
The Workshop treats these radon diagnostic subjects in depth, looking
at the pros and cons of diagnosing the radon troubled house before, during
and after mitigation. The techniques described are evolving rapidly in a
field where discoveries are being made daily. However, many of the
diagnostic approaches may already be viewed as "standard", while many
others are in the process of being finalized.
The principal conclusions of the discussions of each phase of the
diagnostics are given in the following summaries.
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Radon Diagnostics Workshop, 1987. Phase I Summary
PART A WORKSHOP SUMMARIES
Phase I. - SUMMARY
RADON PROBLEM ASSESSMENT DIAGNOSTICS M. Mardis, Chairman
1. Gamma Scans
The National Uranium Resource Evaluation (NURE overflight data)
would most likely be useful in identifying large land areas which would
exhibit a higher probability of indoor radon problems. However, because
of geological differences, and local hotspots, low readings should not be
interpreted as an absence of a radon problem.
Local gamma surveys such as "scan vans" or "on foot" methods may
prove less useful than NURE global surveys because of the limited
coverage. The van is limited by road access, while on foot surveys may be
limited by time constraints.
Isolated hotspots and depth of the radon sources place limitations
on the information available from the various gamma surveys.
2. Soil Gas Measurements
Soil Gas Measurements are another approach to accessing the
probability of local indoor radon problems. High radon levels in the soil
gas (thousands of pCi/L), combined with soil information (permeability in
particular), can indicate the potential1 for elevated indoor levels.
However, the number of measurements necessary to identify the radon
problem potential for a particular construction lot could cost more than
building radon prevention into a house. Hotspots may be missed in the
survey, even with a large number of samples.
The variability of soil gas measurements (i.e., a 10 to 100 fold
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Radon Diagnostics Workshop, 1987. Phase I Summary
difference in levels within tens of feet) is a function of location (e.g.,
if the measurement is taken directly over a rock fracture or a few feet
away with impermeable soil), and may be a function of soil parameters
including moisture and type of clay or sand.
Soil gas measurements seem to correlate with indoor radon values in
areas where there is very homogeneous soil (Florida) but soil gas and
indoor data do not seem to correlate well in areas with highly non-
homo gene ous soils.
Soil gas measurements could be of use in identifying areas of
concern on a regional, or "housing development" scale but not on a single
lot basis. This could be confounded in an area of variable soil types.
In the comparison of soil gas measuring methods, grab samples are
preferred to alpha track and charcoal canister. Further protocol
development is needed for soil gas measurements (i.e., where, when, how
deep, and what type of measurement to make). Direct measurements of soil
gas and soil permeability are preferred. Samples from at least one meter
depth to avoid atmospheric dilution were recommended. Quality assurance
and quality control procedures need to be developed.
A cost benefit analysis needs to be performed to access the
value/risk of using soil gas measurements versus building radon resistant
houses on a regional and single lot basis. General feeling was that there
would be a negative cost benefit when used on a single lot basis.
Delineation of Terms for discussion of this topic area include:
Radon production = radium decay rate
Radon entry efficiency = indoor radon/soil gas contribution to
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Radon Diagnostics Uorkshop, 1987 - Phase ±
Indoor radon level x 100.
Radon availability Rn cone. In pores x sean migration distance.
Mean migration distance = f (soil characteristics and radon decay
rate)
3. Problem House Identification
The geological and the J5URE data may be useful to focus indoor
screenlng/iaeasureisent surveys. The only way to be sure about a house is
to make a "closed house* measurement.
* Useful surveys could be based on prediction models and/or the "Fan
Out" approach around discovery houses (where "fan out" means the use of
high level houses as the centers for studing nearby hoses).
All screening surveys should base design considerations on:
sampling during winter "closed house" seasons
areas with known elevated indoor levels
sampling more frequently in areas with nsore elevated levels, i.e.,
sample every house in areas where a. large percentage of the
houses sampled resulted in levels 4 pCi/L.
4, Questionnaires
Preliminary screening questionnaires are useful for research house
selection and as an opportunity for mitigators to address whether
confirmation measurements have been performed to substantiate the Indoor
levels. They may also ask questions which would provide basic information
on imajor entry routes, basic construction type, etc.
The preliminary questionnaire could identify activities which the
homeowner could carry out to address the need for professional mitlgEtlor.
asslstance.
Pre-mitigation questionnaires and visual Inspections are perhaps the
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Radon Diagnostics'Workshop, 1987. Phase I Summary
diagnostician's primary and most useful tools. Homeowners should be
consulted, but information could be suspect unless the homeowner can
produce blueprints or pictures.
The length of questionnaires and the questions asked tend to be a
function of the experience of the diagnostician/mitigator and the
construction type. Typical entry routes, if identified with early
questions, might preempt other unnecessary questions or diagnostics.
5. Research Needs
We seem to have a sufficient understanding of the major factors
influencing radon entry and typical entry routes in some construction
types to be effective mitigators in those types. (For example, basements
and perhaps slab-on-grades where subslab ventilation systems have proven
highly effective when reasonable communication is present under the slab.)
There is a need for research in other construction types and
combinations of building types. Basic research concerning radon
production, transport and entry into buildings; so that we may better
understand phenomenon we are dealing with and perhaps develop even better
mitigation and prevention techniques.
More research is needed in modeling and prediction/correlations
between geological factors and indoor levels.
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Radon Diagnostics Workshop, 1987. Phase II Summary
Phase II. - SUMMARY
PRE-MITIGATION DIAGNOSTICS - L. M. Hubbard, Chairman
1. Diagnostic goals of researchers and mitigators.
During discussions of diagnostics techniques in general it is
important to be aware that diagnostic measurements appropriate for
research needs are in many instances different than those appropriate for
use by mitigators. Researchers use pre-mitigation diagnostics to further
their understanding of the basic mechanisms for radon transport into
building structures. Some of the research has been directed towards
developing specific diagnostic techniques that are most useful for
mitigators to use. The mitigator on the other hand is interested in being
able to mitigate a house successfully with a minimum of time invested in
diagnostic measurements. The Phase II discussions attempted to separate
these two approaches to diagnostics.
2. Mitigator current diagnostics
The mitigators present at the workshop explained the diagnostic
techniques they are currently using. They ranged from a visual inspection
of the house to a walk through accompanied by some grab samples and
differential pressure measurements and/or subslab and wall communications
testing. Also discussed, but elaborated on in more detail in the formal
presentations, was Saum's diagnostic technique. His "blower floor"
procedure is tailored to a substructure with sufficient aggregate under
the slab that near ideal conditions for subslab ventilation exist. The
diagnostics are designed to assess the size and location of the system
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Radon Diagnostic Workshop, 1987. Phase II Summary
which should be installed, and have proved very useful under these
conditions.
There was generally agreement by the mitigators that with experience
one can often successfully mitigate a building after only a visual
inspection. This is perhaps true if subslab ventilation is the mitigation
installed, partially because the success of subslab ventilation is
dependent on at least some communication existing under the slab (which
does occur in many homes). A visual inspection by an experienced person
is often enough to decide upon the most expedient location for the subslab
penetrations and the exhaust pipe and fan for the system.
An installation with no diagnostic measurements, however, cannot
assure that either too little or too much air (with an accompanying excess
of basement air) is being drawn into the subslab ventilation system.
Currently, however, many mitigators are using no pre-mitigation
diagnostics. They are installing subslab ventilation systems and using
post mitigation radon concentrations to motivate any necessary system
alteration.
Subslab ventilation is the mitigation system for which the most .
diagnostic measurements have been developed and performed, to date.
The most important and useful test in this category is
communications testing. A vacuum cleaner is commonly used to pump on a
given hole through the slab and the induced change in air flow (speed but
most importantly direction) is monitored through other holes which have
been drilled through the slab and temporarily sealed. In some cases a
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Radon Diagnostics Workshop, 1987. Phase II Summary
variable speed pump is used. Good communication means that sucking on one
hole with a vacuum cleaner will cause air to flow through each of the
other test holes into the subslab space. The same test can be done for
within wall and subslab to wall communications.
3. Researcher current diagnostics
The research community is currently working on quantifying the
degree of communication obtained by a known pumping source (and how much
is necessary to maintain subslab depressurization under a variety of
conditions) by measuring the air speed and direction and pressure
differential through each test hole under a variety of conditions.
Grab samples are used in pre-mitigation diagnostics to determine the
location of radon hotspots. This can be attempted by collecting grab
samples from various test holes through the slab, in the hollow block
walls (if they exist), and in any cracks or holes or sumps that exist.
The radon concentrations in these various spots, along with the air
velocity and the cross sectional area through which the air is moving,
will give an estimation of the radon source strength at each test
location.
Grab samples of soil gas collected outside the perimeter of the
house (generally from metal pipes which extend one meter below the soil
surface) along with a soil permeability measurement at the same location
have been used (mostly by researchers searching for some association
between soil gas radon concentration and soil permeability) to determine
which sides of the house may need more attention in the design of the
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Radon Diagnostics Workshop, 1987. Phase II Summary
subslab ventilation system, i.e. where the radon entry points may be the
most significant. Unfortunately this diagnostic procedure has not proven
to. be very useful.
4. Blower door testing
Blower door tests are used for a variety of purposes in pre-
mitigation diagnostics. Regular blower door tests, which relate the-
amount of air flow into (or out of) a house which maintains a specific
amount of pressurization (or depressurization), are used to estimate the
effective leakage area, i.e., the "leakiness" associated with a particular
house. If the test is applied to the basement area alone it is possible
to determine the amount of air flow necessary to maintain a basement
pressurization of between 5 and 10 Pascals. This is the amount of
counter-pressure which should be sufficient to prevent convective entry of
radon gas. If the air flow determined from the blower door test is less
that about 350 cfm, (ideally below 200 cfm), basement pressurization may
be a viable mitigation strategy if subslab ventilation is not suitable.
Another use of a blower door test is to determine what amount of air
exchange is needed in the basement or crawlspace for a Heat Recovery
Ventilator to effectively remediate a radon problem.
A depressurization of the substructure to -10 Pascals can be used in
the summer to simulate winter conditions, although there is some question
as to the reality of this simulation. In this -10 Pascal depressurized
mode, grab samples, pressure differentials, and air velocities through the
test holes can be recorded (as described above) and used to determine
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Radon Diagnostics Workshop, 1987. Phase II Summary
radon source strengths at specific points in the depressurized mode.
5. Tracer gas measurements
Tracer gas measurements can be used in pre-mitigation diagnostics to
augment communications testing. Also, leaks through the exterior of the
substructure can be located using tracer gas techniques (and sealed if a
tighter basement is necessary for success of a basement pressurization
system). Tracer gases can be used for finding a footer drain.
6. Grab sample questions
Questions still remain regarding the extent to which grab samples
should be used. Questions arise because of the diurnal and seasonal
variability in the radon content of the soil and subslab gas and the
dependence of this variability on both environmental and house specific
parameters. These variations need to be better characterized.
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Radon Diagnostics Workshop, 1987. Phase III Summary
Phase III - SUMMARY
MITIGATION INSTALLATION DIAGNOSTICS - M. Osborne, Chairman
Four distinct radon mitigation approaches were discussed along with
their related diagnostic procedures.
1. Sealing
Sealing was the first mitigation method mentioned, where Canadian
studies indicate that a total area equal to one square centimeter opening
in the basement slab or walls is all that can be allowed if the sealing
approach is to be successful. Quality control is extremely important, as
well as the choice of materials. Epoxies often don't bond well with
themselves; they require special surface preparation, and bonding to the
surroundings is vital.
Sealing is viewed as expensive and difficult but not an impossible
task. The best success would be anticipated in new construction where one
needs, an experienced team using common sense in the choice of sealing
methods. A specific recommendation was the use of a sealant such as a
solvent-hardening, rubberized asphalt.
Radon flux measurements. as a diagnostics tool, point out the
effects of even pinhole leaks. Tracer gas methods are also recommended as
a method of assessing radon leakage paths and whether or not sealing is
successful.
2. Dilution
Dilution was the second general method discussed for radon
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Radon Diagnostics Workshop, 1987. Phase III Summary
mitigation. Cautions with this approach include making certain the
airintake isn't near radon sources or located close to the ground, and
avoiding short circuiting (air exiting prior to complete mixing).
The ultimate desire is to set up a plug flow situation, i.e., where
an air flow sweeps away pollutants rather than mixing them with interior
air.
Diagnostics for dilution methods include the use of the blower door
to evaluate the envelope leakage rate of the house as well as to catalog
bypass leakage areas which allow radon to move within the building. For
example, unless appropriate tightness levels are present it may make no
sense to use heat recovery ventilation. The blower door tests can also be
used to evaluate communication between zones. Pressure measurements can
be used to make sure that pressures indoors are slightly positive rather
than negative to avoid drawing radon into a living area.
Air flow measurements may make use of pitot tubes, heated-wire
anemometers, vane-type anemometers, etc., in ducts or pipes. A grid-type
measurement, such as a pitot tube grid, is a superior approach to
averaging flow profiles.
Tracer gas measurements are also very useful in flow measurement and
air movements, as well as detecting leaks in the system.
Use of a continuous radon monitor as a diagnostic tool allows
exhaust air radon concentrations to be evaluated, and to make certain
exhaust flow isn't being reintroduced to the house by the supply air.
Because of shorter air residence times, dilution may result in
reduction of working levels greater than the radon levels themselves.
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Radon Diagnostics Workshop, 1987. Phase III Summary
Radon profiles (multi-location testing) may be used to check for hotspots.
One approach is to flush out the radon with high initial ventilation and
then observe the ingrowth of radon. This diagnostic method may be used to
evaluate the amount of ventilation required to meet EPA guidelines.
3. Pressurization
Pressurization of the basement was the third category discussed.
Separation of the basement/crawlspace from the upstairs is an initial
requirement. If upstairs air is used to pressurize the basement, care
must be taken with the venting of upstairs combustion devices.
Use of the blower door is recommended to check for air leaks between
zones, crack leakage to the outside, and back drafting of appliances.
Flows of approximately 500 cfm, and pressure differences of at least three.
pascals are provided as representative numbers for judging airflow
requirements for pressurization.
Turning on all venting appliances and checking whether the system
maintains proper pressurization is one way to check performance adequacy
of the ventilation system.
4. Subslab depressurization
Subslab depressurization was the fourth approach discussed. Using
the slab as the separation between house space and soil gas
depressurization of the subslab must be sufficient to overcome stack
effects (buoyant airflow in the house that depressurizes the basement) and
venting appliance operation since the resulting basement depressurization
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Radon Diagnostics Workshop, 1987. Phase III Summary
can cause soil gas to move through the slab and walls to the living space.
Sensitive pressure measurement techniques (such as electronic
digital manometers) may be used for evaluating the pressure differences
and smoke tracers can determine the direction of air movement. The lowest
pressure drop locations across the slab are the critical zones and should
not be located near any radon hotspots.
Since the exhaust from subslab depressurization tends to contain
high radon concentrations, avoiding re-entrainment is essential; tracer
gas techniques work well in this check.
The exhaust also often contains high levels of moisture, making it
essential to design piping to avoid water accumulation and eliminate
possible pipe blockage.
Again back drafting of the combustion appliance can be influenced by
the operation of the radon mitigation system since air is being removed
from the house substructure. Indication of spilling of exhaust products
into the space may be documented by a small temperature-sensitive "tab" at
the flue entry. Spillage tends to be worst at start of combustion
appliance operation. Use of blower door techniques can also supply
information on the required air leakage necessary to supply combustion
devices. Dedicated make up air to the appliance is highly desirable.
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Radon Diagnostics Workshop, 1987. Phase IV Summary
Phase IV. - SUMMARY
POST MITIGATION DIAGNOSTICS - B. Henschel, Chairman
Radon monitoring
o Radon monitoring.is the principal post mitigation diagnostic test commonly
utilized by commercial mitigators. The first question is -- should the emphasis
be on measurement of radon or radon proEenv? Currently most people measure
radon gas. One reason is that it is simpler to measure radon gas -- i.e.,
charcoal canisters, and alpha track detectors. Radon measurements might provide
a less ambiguous indication of mitigation performance. Radon might even provide
a better indication of health risk (given that only a relatively inexpensive
measurement can be made, and that the WL - versus - particle size measurements
needed for dosage/risk models are thus impractical for routine use); the radon
is tracked by reading the value for Polonium-218, which -- as the daughter with
the greatest fraction unattached -- probably represents the largest contribution
to the health risk. There is a need for technical clarification of the EPA
guideline of 4 pCi/L or 0.02.WL because it is known that the equilibrium value
relating radon and radon progeny varies by up to fifty percent. From a policy
perspective, however, the guideline is sufficient as it is expressed (4 pCi/L
or 0.02WL) because no specific equilibrium condition is specified or implied.
In other words, the EPA action level is reached when concentrations of radon
exceed 4 pCi/L or radon progeny exceed 0.02WL.
2. Who makes the measurements?
o Post mitigation radon monitoring also involves the question of who
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Radon Diagnostics Workshop, 1987. Phase IV Summary
makes the measurement? A mitigator faced with the question of liability
needs a direct knowledge of how the mitigation system is functioning.
Also, information on the success of the mitigation method aids the
mitigator in selecting mitigation approaches for other homes. The
homeowner is concerned that the problem has really been solved and might
want an independent measurement, made by someone other than the mitigator.
Federal or state government representatives may be most interested in how
well the mitigators are performing from a public health standpoint, and
therefore may desire an independent evaluation of radon levels. These
results may dictate which mitigators are placed on a "recommended list",
where states maintain such a list.
3. Length of testing
The next question involves the length of testing. Short-term
monitoring is essential, immediately after radon mitigation system
installation, to confirm that the system is functioning properly. In
addition to this immediate measurement, an integrated measurement over two
to three months (alpha track) in the winter (to provide a worst case test
of the system over a reasonable time period) is a recommended minimum
evaluation.
The need to develop two-week monitors as an intermediate measure was
also discussed.
Arriving at an annual average radon exposure is a point that needs
further clarification; if the 4 pCi/L guideline is interpreted as the
annual average that a homeowner should try to achieve, then measurements
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Radon Diagnostics Workshop, 1987. Phase IV Summary
might cover a full year.
Multi-year monitoring could be valuable in evaluating changes in
mitigation system efficiency and/or variations in the radon source
strength over time. Annual and multiyear measurements would probably not
be conducted by the mitigator, but would be the responsibility of the
homeowner, or might be carried out by researchers or state agencies.
Inexpensive monitoring devices may be heading to the market place to
help solve some of these radon monitoring problems.
4. Where do you monitor?
Measurements are normally done in more than one location: in the
living area, both upstairs and downstairs, in the basement/crawlspace, and
in those locations cited by the homeowner as important. Protocols must
specify monitoring location.
By surveying the radon levels throughout the house (radon profile),
one is less likely to miss a high radon area, and also these data can be
the basis for estimating total occupant radon exposure. The basement (or
perhaps crawlspace) area normally registers the highest radon levels and
thus is most sensitive in revealing if any radon problem still exists
after mitigation.
5. What monitoring techniques are being used?
Charcoal canisters and alpha track detectors are popular because of
ease of use and relatively low cost. For immediate radon level
information, grab and continuous radon sampling are popular. There remain
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Radon Diagnostics Workshop, 1987. Phase IV Summary
several uncertainties associated with the interpretation of grab sample
data because of the large variation in indoor radon levels (which is
evident from continuous radon data).
In view of all the uncertainties, there would appear to be a need
for a standardized procedure that could be routinely applied in the post
mitigation period.
6. Other diagnostics
Diagnostics other than checking radon concentrations are usually not
done routinely by commercial mitigators.
Testing of the final pressure field under the slab after
installation of a subslab ventilation system was emphasized by several of
the workshop participants as an important item to consider as a post
mitigation diagnostic measurement.
Assurance that combustion devices are not back drafting is also an
important post mitigation measurement to make.
Measurement of flows and pressures in the piping associated with the
mitigation system can be important in the post mitigation diagnostics as
well as during system installation.
Mounting a gauge on the piping to indicate proper system function is
being used and is a form of post mitigation diagnostics that provide
assurance to the homeowner that the system is functioning satisfactorily.
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B. WORKSHOP PRESENTATIONS
The following presentations preceded the actual workshop discussions.
The purpose was to introduce the workshop attendees to the spectrum of
radon diagnostic subject matter presented by researchers and practitioners
who represented the cutting edge of radon diagnostics and mitigation
technology. These presentations, of necessity, were concise, but the
workshop participants were given adequate time to pose questions to gain
more detailed information on those areas of particular interest. Further
references were provided in many instances, and a reference section has
also been included in this workshop summary.
18
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The worse descrisea in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
GENERAL CONSIDERATIONS
RELATED TO RADON DIAGNOSTICS
J. Tell Tappan
ARIX Sciences Inc.
Grand Junction, CO 81501
1.0 INTRODUCTION
Numerous diagnostic techniques have been used for determining the
existence and extent of a radon problem. These techniques are generally
categorized in four sequential phases; initial problem assessment, pre-
mitigation. mitigation installation, and post-mitigation. This paper
presents a general overview of the various techniques used during these
four basic phases of diagnostics.
2.0 INITIAL PROBLEM ASSESSMENT
Diagnostic techniques used for this phase can be applied to open land
areas, as well as existing structures and their sites. The normal
approach includes identifying areas that are geologically prone to radon,
and then surveying specific sites within the radon-prone area to confirm
the presence of a radon problem. The sequence of diagnostics related to
this initial assessment is discussed below.
2.1 Geologic Characterization
A review of individual state .geologic maps serves as the basis for
identifying potentially elevated radon areas. The primary geologic
formations that accommodate elevated radon are as follows:
Granitic Rocks
Granitic formations are generally associated with higher
concentrations of uranium than other formations. The uranium
enrichment occurs naturally due to the geochemical composition.
Additionally, fractures are routinely associated with granites,
and the fractures accommodate remobilization and concentration of
uranium within the fractured areas.
Marine Black Shales
These formations are primarily carbonaceous (plant derived
material) shales, and in many cases low concentrations or seams
of coal are related to the shales. The carbonaceous materials
tend to absorb uranium during initial deposition. Additionally,
uranium migration associated with ground water results in
enriching the carbonaceous materials, since these materials
essentially act like a sponge relative to the radioactive
materials.
19
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Silty Shale Containing Phosphate
These formations are always naturally enriched with uranium.
Many phosphate milling operations actually reclaim the uranium
(yellow cake) from the phosphate tailings on a profitable basis.
It is not uncommon to find uranium concentrations ranging from 50
to 100 ppm in these formations.
Thorium and Rare-Earth Occurrence
These occurrences are generally related to several geologic
characteristics; alkalic rocks, carbonatites, senites, granites.
and in veins. The U.S. Geological Survey has two open-file
reports, 79-576T and 79-576U, that have mapped these occurrences
within the conterminous United States.
Soil Permeability
Review of state geologic maps can assist in characterizing
permeability of soils that overlay geologic formations of
concern. These data are useful in estimating radon emanation to
the soil surface.
2.2 Gamia-Ray Anomalies
Gamma-ray anomalies can be related to daughter products of
uranium, thorium, and potassium. In the case of uranium, the
daughter product bismuth-214 (which is also a radon daughter) can
contribute to the gamma-ray anomaly. Identification of these
anomalies is generally based on a historical data review and
field surveys as follows:
Historical Data
In 197A, the U.S. Department of Energy (DOE) initiated the
National Uranium Resource Evaluation (NURE) program. This was
prompted by the need to address concerns over the available
uranium supply for nuclear reactors. Aerial radiometric surveys
were flown, using sensitive gamma-ray spectrometers_that measured
uranium, thorium, potassium, and bismuth. All but four of the
quadrangles in the conterminous 48 states were surveyed; 99 of
154 quadrangles in Alaska were also flown. The flight line
spacing varied from a quarter mile in detailed surveys to six
miles in areas not expected to contain significant uranium
concentrations. Maps produced by the DOE depicting the uranium
occurrences identified by this survey are useful in defining the
naturally-occurring concentrations of radon on a regional basis.
20
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Many states have completed gamma-ray surveys using mobile gamma
scanning vans or hand-held portable gamma scintillometers. These
survey results have been mapped by the appropriate states and
they are useful in defining near-surface anomalies that will
produce radon problems.
Field Surveys
A gamma-ray scintillation detector incorporating a multi-channel
analyzer has been mounted on a van-type vehicle to accommodate a
mobile survey within areas of concern. The detector is normally
shielded to direct sensitivity to a single side of the mobile
unit. A recorder is incorporated with the system, and recorded
gamma anomalies are related to physical location by hand.
Accumulated- data are useful in identifying specific structures or
building sites where there is a high probability of elevated
radon.
Gamma-ray surveys are also performed on foot using hand-held
scintillometers. For individual building sites a scanning
technique, with the detector about two inches above the surface,
is used and data are recorded on a 10-foot grid basis. Existing
structures are also thoroughly scanned and data are recorded on
an appropriate floor/plot plan sketch. Anomalies identified are
useful in identifying specific "hot" spots where elevated radon
is likely.
2.3 Soil Radon Gas and Flux Rate Measurements
Soil radon characterizations are particularly useful in diagnosing
open ground areas planned as building sites. Two techniques are
normally used; one that measures the radon concentration contained
in the near surface soils, and one that measures the radon flux rate
on the surface area. These techniques are discussed below.
Soil Gas Radon Concentrations
Alpha track film detectors are normally used to make these
measurements. The detectors are normally placed on the surface
soil in a grid pattern over the area of interest; areas where
gamma-ray anomalies have been identified are always included in
the sampling. Detectors are also placed over or within soil
boreholes of varying depths to accommodate soil gas measurements
from subsurface soil layers. Data from the alpha track film are
plotted on an appropriate plot plan map; this mapping shows a
soil gas profile over the area of interest. These data are
useful in determining the soil radon concentration related to a
specific location planned for building. To date, a precise
method for relating these measurements to an indoor radon
concentration has not be determined.
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Radon Flux Measurements
Two radon flux measurement techniques are commonly used; charcoal
absorption and accumulator. Since radon transport or migration
through soil is highly dependent on soil permeability, moisture
and several other parameters, flux measurements are normally made
at the location of a hole (dug or bored) that represent the
footing depth of the planned structure. Measurements are made in
units of pico-Curies of radon per square meter (pCi/m^). The
resulting data is related to a flux rate of < 2 pCi/m^ which is
associated with soils where the habitable structures do not
contain elevated radon concentrations. Areas measuring in excess
of 2 pCi/m^ can be expected to produce a radon problem in an
enclosed structure.
2.4 Structural and Occupancy Characteristics
Visual inspection of the structure and general habits of the
occupants are important factors related to indoor radon problems.
The structure design and condition of structural components have a
direct relationship to the problem since these parameters can either
produce a radon barrier or an influx route. Additionally, occupancy
characteristics have a significant relationship to the air exchange
rate and indoor pressure differentials associated with the
structure. Techniques normally used to diagnose these
characteristics are discussed below.
Visual Structure Inspection
This technique includes identification of apparent major radon
influx routes such as open soil areas, sumps, structural cracks,
fence drains, porosity of structural components, and use of
exhaust fans. These observations are normally recorded on a
standardized form, and the data is useful for evaluating
complexity relative to possible remediation.
Occupancy Characteristics
This technique includes having the occupants fill out a
standardized form indicating the number and age of occupants,
smoking habits, occupants that work outside the home, and other
data that can be related to the occupant-induced ventilation of
the structure. Additionally, other related data are normally
obtained during structure inspections through conversation-with
the occupant.
2.5 Indoor Radon Profile
This diagnostic effort includes measurement of radon and radon
decay-product concentration (RDC) in various zones or regions of a
habitable structure. Several measurement techniques are routinely
used that can generally be categorized in three groups; grab
sampling, integrated monitoring, and continuous monitoring.
22
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Resulting data are useful in identifying concentration gradients
that indicate regions of significant radon influx or stagnant air.
Additionally, simultaneous radon/RDC measurements will identify the
equilibrium state of the decay product, and the age (equilibrium
state) of the decay products can be related to the air exchange rate
of the structure. The techniques used to obtain this profile data
are discussed below.
Grab Sampling
This technique includes collecting simultaneous radon and RDC
measurements from various locations representing all indoor areas
of the home. Equipment includes radon scintillation cells, low
volume air sample pumps incorporating a glass fiber filler, and
appropriate photo-multiplier tube detectors with sealers.
The number and location of samples required is site specific
depending on the number of floor levels and configurations of
room partitioning associated with the home. The following sample
location selection criteria will generally apply:
Basement - Usually a minimum of two locations, one in either
end; however, can require four locations in basic quadrants if
partitioning indicates isolation of one area from another.
Crawl spaces - Usually one location near the center of the
crawl space, followed by one location in the living space
directly above the crawl space location.
Main floor above basement - Usually a minimum of two
locations, one in the main living space and one in the
opposite end of the house in a closed bedroom.
Third level of two story house - Usually one location from
closed bedroom; an additional sample is required if open
living area is present.
In summary, radon profile sample locations required for each home
will vary from a minimum of 4 to as many as 9.
Accumulated data are normally summarized on an appropriate
"standard" form. The radon and related RDC is recorded for each
sample location, and the equilibrium state of the RDC is
calculated for each location. These data are averaged to show
the overall house radon and decay product concentrations as well
as the average equilibrium state.
23
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With respect to the measured equilibrium. 50-percent equilibrium
is equivalent to 38 minute old radon decay products, which
equates to approximately 1.6 air exchanges per hour. This
information is a "rule of thumb", since decay product plate-out
and other factors are ignored. However, the data is useful in
determining structure ventilation prior to and during sampling,
and it serves as a good indicator of the validity of the sampling
effort.
Integrated Monitoring
Carbon canisters, alpha track film, and the Environmental
Protection Agency (EPA) Radon Progeny Integrating Sampling Unit
(RPISU) are commonly used to accommodate this radon profiling
technique. The sampling device is placed in a single area of
interest, or in various regions of the house as discussed in
relation to grab sampling.
Normally measurements are made over a 2 to 5 day period, and
results are interpreted over this sampling period. These data are
useful in identifying areas of primary radon influx, as well as
for confirming the presence of an indoor radon problem.
Continuous Monitoring
Several manufactures produce continuous monitors for measuring
radon or radon decay-product concentrations. These monitors are
deployed in a specific area of concern or various zones of the
indoor area. Sampling periods should be a minimum of one hour,
and sampling periods of up to several days can be accommodated.
Resulting data are useful in providing relatively prompt
information regarding concentration gradients, and confirmation
of a radon problem is easily obtained.
3.0 PRB-MITIGATION
This phase of diagnostics accommodates collection of data from indoor
areas, and these data are the basis for identifying appropriate site
specific radon mitigation techniques that can be applied to the
structure. The basic techniques used can be generalized in three
categories; radon grab sampling of structural components or zones, radon
flux rate measurements from structural components or features, and
pressure measurements and alterations. These techniques are briefly
discussed below.
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3.1 Radon Grab Sampling
Flow-through type radon scintillation cells are normally used to
accommodate this diagnostic effort. Samples are collected from
inside hollow walls (through a drill hole or from behind an
electrical switch plate), from water drain sumps, from beneath
concrete floor slabs (through drilled holes), or any other
structural component or area of interest. Resulting data identifies
areas or components with significant radon concentrations that may
be suspected as major contributors to the indoor radon problem.
3.2 Radon Flux Measurements
The charcoal absorption or accumulator methods are normally used to
accommodate these measurements. The sampling device is sealed over
the surface area of interest for a timed interval, and resulting
data is calculated in pCi/m^. Sample collection locations normally
include each basement foundation wall, the floor/wall joint, the
solid floor, and any structural cracks that could accommodate
significant radon entry. The accumulated data provides a comparison
of the radon source significance related to structural components or
features sampled. This information aids in determining which
structural feature should be mitigated to obtain the most
significant radon reduction.
3.3 Pressure Measurements and Alterations
These diagnostics normally incorporate use of fans, blower doors,
pressure and air flow rate measurement devices, and tracer in gases.
Pressure differentials are measured in areas of interest and indoor
zones. Specific areas or zones in the house are pressurized or
depressurized through use of' fans, connections through floor slabs
or into walls, and blower doors as appropriate. Radon sampling is
normally performed between each induced pressure change to determine
the effect on radon concentrations.
Air movement and velocities are measured through structural test
holes to identify communication from one point to another. Inert
tracer gases are often injected in areas of interest and resulting
measurements are also used to determine communication between
specific points.
Blower door tests or inert tracer gas injections are normally used
to evaluate the building envelop tightness. These techniques will
be discussed in detail by other workshop participants.
25
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In summary, pressures are recognized as a dominating factor relative
to radon influx rates. Diagnostic techniques used are highly
variable as is the equipment incorporated with the techniques.
Information gathered is useful for determining the effect of
occupant or meteriologically induced pressure charges.
4.0 MITIGATION INSTALLATION
Diagnostics used for this phase include measurements and observations to
assure the quality and integrity of the installed mitigation system.
These parameters are discussed below:
4.1 System Quality
The primary quality factors are materials used, craftsmanship
applied, and the cosmetic effect the system has on the interior
area. Quality products must be used, and installation must be
accomplished using industry craftsmanship standards. In all cases,
system installation should be accomplished in a cosmetically
acceptable and pleasing manner to the extent that is practical.
4.2 System Integrity
Diagnostics to assure system integrity includes balancing air flow
within the system, tracer gas injections to identify leakage or
determine exhaust backdraft, and pressure differential measurements
in specific areas or zones.
Simple smoke tube techniques can usually identify significant single
point system leaka-ge or backdrafts, however, other tracer gases
injected into the system will provide better identification of
leakage related to several small points that are significant when
combined.
Pressure differential measurements from specific areas and zones
will identify system induced changes that may affect the radon
influx. It is possible to create a negative pressure with an active
mitigation system, and this will normally result in increased radon
influx. Conversely, over pressurization of a radon influx zone will
either reduce the influx rate or force increased radon
concentrations into other areas of the structure.
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5 .0 POST-MITIGATION
Diagnostics related to this phase will identify the most efficient
operational mode of the mitigation system, and evaluate the systems
overall performance relative to desired indoor radon reduction. After
the operational efficiency and overall effectiveness of the system has
been determined, various appropriate diagnostic measurements discussed
previously may be required in the event indoor radon concentrations
remain above the desired level. These aspects of diagnostics are
discussed below.
5.1 Effectiveness Evaluation
The indoor radon profiling techniques, previously discussed in
Section 2.5. are normally used to determine radon/radon decay-
product concentrations in various areas or zones throughout the
structure after the mitigation system is activated. These data
provide relatively prompt information regarding radon reduction
achieved. If the mitigation system incorporates blowers or fans,
speeds of these units are increased or decreased to obtain maximum
radon removal and energy efficiency; re-sampling radon profile
locations is accomplished after each adjustment to accommodate this
evaluation.
5 .2 Additional Remediation Considerations
If the post-mitigation effectiveness diagnostics indicate need for
additional remediation, various techniques (discussed previously)
are used to determine appropriate options. Since these techniques
have been discussed previously, the following simply lists
techniques commonly used in the order of personal preferences:
Radon flux rate measurements to determine primary structural
contributors remaining.
Radon grab sampling from structural areas sampled during pre-
mitigation diagnostics and other suspect areas to determine
elevated sources remaining.
Re-measurement of delta pressures, air flow rates, and air
movement directions to determine need for further system
balancing.
Additional visual examination of structure characteristics to
identify any possible oversights.
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This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication.
Use of Vehicle-Mounted Radiological Equipment
in the Diagnosis of Houses with Elevated Levels of
Radon and Its Short-Lived Progeny
C. S. Dudney, B. A. Berven,
T. G. Matthews, and A. R. Hawthorne
Health and Safety Research Division
Oak Ridge National Laboratory
Oak Ridge, TN 37831
I. Introduction
Since^he discovery of American homes with levels of indoor
radon progeny far in excess of the levels allowed in
underground mines by governmental regulations, there has
been greatly increased awareness of radon in residential
environments. Homes with high levels of indoor radon have
also been identified in .Scandinavia. Underground miners
exposed to radon progeny have experienced elevated incidence
of fatal lung cancers and it is suspected that residential
exposure may also lead to cases of lung cancer. Nero et al.
(1986) have estimated that 1 to 3% of American homes have
annual average levels of radon in excess'Of 296 Bq/m . The
federal government (U.S. EPA and CDC, 1986) has estimated
that lifetime exposure to levels of radon above 296 Bg/ro3
will increase lifetime absolute'risk of fatal lung cancer by
at least 26 chances in 1000.
Many factors are important in the identification of houses
with elevated levels of radon. Since indoor radon comes
predominantly from the rock and soil near a house,
geological factors are important. Occupant behavior,
building structure and weather are important factors because
exchange of indoor and outdoor air is a principal means of
dilution of indoor radon. This paper will briefly discuss
the use of vehicle-mounted equipment in the assessment of
Research sponsored by the U.S. Environmental Protection
Agency under Interagency Agreement No. 40-1709-85, by the
Tennessee Valley Authority under Interagency Agreement No.
40-1459-84, and by the Offices of Health and Environmental
Research and of Remedial Action and Waste Technology of the
U.S. Department of Energy under Martin Marietta Energy
Systems, Inc., contract No. DE-AC05-840R21400 with the U.S.
Department of Energy.
References to radon in this paper refer to 222Rn unless
otherwise noted.
28
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some of these factors, principally building and geological
ones, in studies that either seek to identify houses of
concern or to identify radon entry points and sources in
selected houses. Emphasis will be given to work that has
been performed by Oak Ridge National Laboratory (ORKL) staff
during the last ten years.
II. Description of Vehicles
Two principal types of vehicles have been used by ORKL staff
in their radiological surveys. The radiological scanning
vehicles have been used to investigate spatially dependent
anomalies in the gamr.a radiation field at selected
locations. The mobile radiological laboratory has been used
to provide logistical support to surveys requiring
radiological measurer.ents at sites that may lack electrical
power or other requirements.
A. Scanning Van
A mobile garnr^a scanning system has been developed for the
U.S. Department of Energy (DOE) by ORNL staff. The unit was
originally developed in 1979 and its performance was
enhanced following a research and development project in
1981. The vehicle provides continuous nuclide-specific
analyses while in motion.
The detection system consists of a Nal(Tl) crystal, shielded
so that photons principally originating from the passenger
side of the vehicle are detected. The system is controlled
by the operator through an on-board computer, with data
output provided to the computer monitor, strip chart
recorders, and a printer. Data are also stored onto floppy
disks. Multichannel analysis capabilities are provided for
qualitative radionuclide identifications. A 22°Ra-specific
algorithm is currently employed to identify locations
containing residual radium-bearing materials.
The primary mission of the mobile scanning van is to locate
and identify those building lots on which there is evidence
of residual radioactive material above local background
levels. Typically, the scanning surveys are conducted as
the final stage of the identification process and are used
to (1) document locations that were identified from
historical records, (2) provide ground-level surveying in
support of aerial survey efforts, and (3) screen large areas
of a residential neighborhood on a street-by-street basis.
In identifying lots where contaminated materials exist, the
scanning system is used to detect changes in the gamma
radiation field associated with the site, as observed from
accessible roadways or other public thoroughfares.
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B. Mobile Radiological Laboratory
The staff at ORNL have also developed two mobile
radiological laboratories. During surveys, a mobile
laboratory can serve as a control center as well as housing
instruments and other needed equipment. Each vehicle is a
modified motor home equipped with its own electric
generator, desktop computer, and radiological instruments.
The radiological capabilities pertinent to radon diagnosis
that can be performed on site include analysis of short-term
samples for airborne radon and airborne progeny from 222Rn,
2 Rn, and 2^Rn. A detailed description of these
techniques is given below. In addition, crude radiological
analyses of soil can be performed using Nal(Tl) well
detectors.
III. Identification of Houses for Further Study
Because only a small fraction of U.S. houses are currently
thought to require remediation for radon progeny exposures,
it will be necessary to identify those residences needing
further evaluation. In cases where the radon precursors are
inhomogeneously distributed in the soil, it has been
possible to investigate the gamma radiation field near
houses while avoiding intrusions onto private property by
using the mobile scanning van. These kinds of studies have
allowed investigators to target residences for more detailed
assessments. In cases where radon precursors are more
homogeneously distributed, the only methods identified so
far for identification of potential problem areas have
involved geological assessment or untargeted measurements
within houses and will not be discussed here.
A. Uranium Kill Tailings
Currently there is a large ORNL field office near Grand
Junction, Colorado, out of which health physicists,
geologists, and other ORNL staff are assisting in the
identification of houses and building lots that are eligible
for remediation under the Uranium Mill Tailings Remedial
Action Project. Federal law, as implemented by 40CFR192,
stipulates that DOE will offer to remediate buildings or
homes at which there is evidence of mill tailings from the
government's uranium mining programs in the 1940's and
1950's. Properties can qualify in various ways for this
program, one of which is demonstrating both annual average
radon progeny levels in excess of 0.02 WL and the presence
of uranium mill tailings. This program provides for the
One working level (WL) means any combination of short-lived
radon progeny in one liter of air that will result in the
ultimate emission of 1.3 x 105 MeV of potential alpha
energy.
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removal and replacement of soil around qualifying buildings
and residences.
To facilitate the completion of this program, radiological
scanning vehicles have been used to identify potential
candidate houses without intruding on building occupants.
By slowly driving the scan van, described in Section II.A,
down public roads it is possible to flag sites of
radiological anomalies. In this case, the anomalies for
which a search is made are those related to emissions from
226Ra or 232Th progeny.
B. Radioactive Waste from Dump Sites
There is a similar need for remediation in areas where soil
from radiologically contaminated landfills has been used for
backfill around homes. For example, in West Orange, New
Jersey, waste from a radium dial painting facility was
disposed of at several landfills in the 1930's and 1.940's.
Subsequently, houses were built above some of these
landfills and there is now an effort to remove the radium-
containing soil from near the adversely affected houses.
When there is reason to suspect that some homes in a region
may have a problem but it is not possible to identify them
explicitly from historical records, then the use of a scan
van or similar vehicle may be warranted.
IV. Identification of Sources Within the House
After a house has been identified as having a radon problem,
there are potential uses for vehicle-mounted equipment in
the identification of points of entry- The techniques
historically used at ORNL will be discussed here. With the
recent advent of more compact, light-weight electronic
equipment, alternative methods are available to make some of
these assessments.
A. Radon
Air samples collected near a single point in space and over
a relatively short interval of time (i.e., less than 5 min),
can be used to estimate the spatial distribution of radon
levels within a residence. In this way, entry points with
significant elevation of radon gas may be located.
A modified Lucas cell is used to measure radon (Volchok and
dePlanque, 1985). The cell consists of a 500-mL plastic
flask with interior surfaces coated with zinc sulfide. Room
air is transferred into the flask and it is held for at
least 4 h to let all preexisting radon progeny decay. The
flask is then placed in a counting well on the vehicle and
total alpha activity determined with a photomultiplier and a
single channel analyzer. Currently, there are commercially
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available, battery-powered, portable systems that perform
the same function.
B. Radon and Thoron Progeny
Another indicator of radon (or thoron,' 220Rn) entry points
is measurement of progeny levels to estimate the spatial
distribution. Due to the short half-lives of these species,
more complex techniques are employed to measure levels of
specific airborne progeny.
To collect a sample of airborne radon or thoron progeny,
room air is pumped through a filter with pore size less than
one micron. Most progeny, both attached and unattached to
particulate matter, will be trapped on the filter and can be
analyzed for alpha activity. The protocol used at ORNL has
called for drawing 100-200 L through a 0.45 urn filter in ten
min. The filter is then taken to the mobile radiological
laboratory and mounted below a surface barrier detector with
helium gas flowing over the surface of the exposed filter.
The heliur. serves to reduce the energy dispersion of
observed disintegrations of any given alpha energy. Between
2 and 12 min and between 15 and 30 min after the cessation
of pumping, energy-resolved data from the detector are
acquired into a 512-channel analyzer. Using the algorithms
of Perdue et al. (1980), concentrations of progeny from
222Rn, 22 Rn, and 219Rn can be estimated.
C. Working Level Ratio
Another indicator of radon entry points that may be used in
the future is the ratio of progeny levels to radon levels.
As radon-containing air ages, the progeny to radon ratio
increases. Using the techniques described above or
equivalent ones, it is possible to measure radon and its
progeny at nearly simultaneous times at several locations.
Figure 1 summarizes data from a survey of 70 houses in four
states and shows that on average, air in basements has a 36%
lower ratio of progeny to radon compared to air sampled on
the floor above the basement.
V. Identification of Sources Away from the House
The scanning van has been used to investigate the relative
abundance of 226Ra in various geological strata near some
houses with elevated radon levels. In Huntsville, Ala.,
four of eight houses studied had radon levels between 740
and 2220 Bq/m (Dudney et al., 1987). A team of geologists
investigated the geological strata in Madison County to
determine which strata contained significant levels of
226Ra. Of eight strata measured, the radium content of
Chattanooga Shale was 20-fold higher than that of any other
stratum. There is a layer of bedrock above the shale and
below the studied houses that is approximately 500 feet
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thick. If we assume that Chattanooga Shale is the source of
most of the radon found in the studied houses, then it has
migrated a substantial distance to reach these houses.
VI. Summary
Vehicle-mounted radiological equipment can be used in a
variety of ways to identify and diagnose houses with radon
problems. Some of the capabilities can be duplicated using
modern portable electronic devices, but not all. In some
cases the presence of a vehicle is needed due to the weight
of shielding required or the presence of generators,
computers, and other equipment for more sophisticated
analyses.
VII. References
Nero, A. V., Schwehr,, M. B., Nazaroff, W. W., and Revzan,
K. L., "Distribution of Airborne Radon-222 Concentrations in
U.S. Homes," Science 234:992-997, 1986.
U.S. Environmental Protection Agency (EPA) and Center for
Disease Control (CDC) of the U.S. Department of Health and
Human Services, 1986, "A Citizen's Guide to Radon," Report
#OPA-86-004, 1986, available from the National Technical
Information Service, Springfield, Va. (USA).
Volchok, H. L., and dePlanque, G., "The EML Procedures
Manual," p. G-25-01 in Report HASL-300, 1985, available from
the National Technical Information Service, Springfield, Va.
(USA).
Perdue, P. T., Leggett, R. W., and Haywood, F. F., "A
Technique for Evaluating Airborne Concentrations of
Daughters of Radon Isotopes," pp. 347-356 in Proceedings of
Third International Symposium on the Natural Radiation
Environment (Eds. T. F. Gesell and W. M. Lowder), 1980,
available from the Technical Information Center of the U.S.
Department of Energy, Oak Ridge, Tn. (USA).
Dudney, C. S., Hawthorne, A. R., Wallace, R. G., and Reed,
R. P., "Levels of Radon and Its Short-Lived Progeny in
Alabama Houses," 1987, Submitted to Health Physics.
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Upstairs equilibrium ratios tend
to be 55% greater than downstairs.
120
Upstairs Ratio (%
100-
80-
60-
40-
20-
0
o
o
o
o
o
o
o o
o
o
o
o
I
10
I
15
I
25
I
35
20 25 30 35 40 45
Downstairs Working Level Ratio (%)
50
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Soil Characterization for Radon Availability and Transport
C. Kunz
Wadsworth Center for Laboratories and Research
N.Y.S. Dept. of Health
Albany, NY 12201
Report for Radon Diagnostics Workshop Princeton University
13-14 April 1987
Introduction
To identify high risk areas and to gain a better understanding of the
causes for above average levels of indoor radon it is necessary to characterize
the surficial soils and bedrock for radon availability and transport. Some of
the measurements and measuring techniques we have used to determine the
availability and transport of radon in surficial soils and bedrock will be
briefly discussed in this report.
The availability of radon refers to the rate of formation of radon in the
gaseous state (soil gas) that is available for transport into homes. The
availability is related to the soil and bedrock radium concentration, the
emanating fraction, soil porosity and soil gas radon concentration. The
transport of radon is related to the permeability (inverse of resistance) of
the soils and bedrock for gas flow.
There is existing information available regarding the radium concentration
and permeability of the surficial soils and bedrock. Most of the U.S. has been
mapped for surficial Y through the National Airbourne Radiometric
Reconnaissance study conducted by the DOE as part of the National Uranium
Resource Evaluation program. These airbourne Nal measurements observe Y
radiation from about the first foot of surficial soil or rock. Latitudinal and
longitudinal flight lines were spaced 3-6 miles and 12-18 miles respectively.
These data should be useful in identifying regions high in surficial radium.
35
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Information from mining and drilling operations is also useful in locating
areas high in bedrock uranium and radium.
For most of the United States there is a great deal of information
available with regard to soil type, depth, water permeability, particle size
and bedrock. Most of the soil information can be obtained from soil
conservation service data. Maps of the surficial bedrock geology are also
available in addition to soil, ground water and bedrock data from sources such
as drilling logs. As the understanding of the relationship of soil gas
permeability and indoor radon improves the available surficial soil and bedrock
information will be of great value in identifying potentially high risk areas.
Surficial Gamma
Surficial gamma measurements were made using Nal survey meters by placing
the meters directly on the ground. In addition to measuring the T flux from
radionuclides in the ground the meters were sensitive to cosmic rays. Long
Island soils with geometric means for U-238, Th-232, Ra-226 and K-40 of 0.9,
0.8, 0.6 and 6.9 respectively averaged 9 yR/hr at the surface. Of this about 3V
R/hr can be attributed to cosmic rays. Shallow soils over black shade in
Onondoga County with geometric means for U-238, Th-232, Ra-226 and K-40 of 2.7,
1.1, 2.3 and 26.7 respectively averaged 14 yR/hr at the surface. We have found
that surficial gamma measurements are easily made and are a good indicator of
surficial soil and bedrock with above average concentrations of Ra-226. It is
possible that high surficial gamma readings are due to above average
concentration of U-238, and/or Th-232, and/or K-40 in soils or rocks with normal
concentrations of Ra226, however, in general this is not the case.
Soil Ra-226
Soil samples of about 1 kgm were usually collected from depths between 2
to 4ft. Occasionally soil profiles were measured by taking samples at every
36
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foot down to 4 feet. The samples were sealed in plastic bags and returned to
the laboratory for analysis. The soils were dried at 100°C, the moisture
content determined, and then passed through a 20 mesh sieve (.841 mm opening).
The gamma spectrum of the fraction passing through the sieve was measured using
either Ge(Li) or Nal detectors. Rock samples were broken and passed
through the same 20 mesh sieve. Samples of about 70 gm were sealed in plastic
bottles for GeLi counting and about 300 gm were sealed in Al cans for Nal
counting. A radon-radon daughter in growth period of 3 weeks in the sealed
container was allowed before counting. In addition to Ra-226, the
concentration of U-238, Th-232 and K-40 were routinely measured.
Portable Y spectroscopy equipment is available and would be very useful
for field measurements of Ra-226.
Soil Gas Rn-222
The concentration of radon in soil gas was measured using both grab
sampling and time integrating techniques. Grab samples were taken by driving a
1/2* diameter pipe into the soil at depths ranging from 1 to 4 ft. (Figure 1).
The end of the pipe was fitted with a driving point and perforated with about
50 small holes (3/32" diameter). The pipe was attached to a diaphram pump .and
air withdrawn at 200 cc/min for 5 min to purge the pipe and lines. A 1-liter
evacuated flask was then filled with soil gas and returned to the laboratory
for Rn-222 measurement using Lucas scintillation cells. Samples were also
measured in the field by flushing scintillation cells with soil gas and
counting with portable photomultiplier equipment. Samples were generally taken
at depths of 2 and 4 ft. The average Rn concentration in soil gas at 4' was about
a factor of 2 greater than observed for samples taken at 2'.
Soil gas radon measurements were also made using alpha track detectors
(Figure 2). Time integrated measurements were made for periods ranging from a
37
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few weeks to several months. A 6 in. hole was augered or dug to depths ranging
from 2 to 4 ft. A three-inch diameter PVC pipe with a reducing fitting on one
end was placed in the hole and the soil tamped into the space around the pipe.
A 1 1/2-in. diameter PVC pipe with a track etch detector attached to the end is
then placed inside the 3 in pipe and threading into the reducing fitting. The
3 in pipe is left in the ground and the alpha track detector periodically
changed by withdrawing the inside pipe. Alpha track detectors with membranes
to exclude thoron are used for soil gas measurements of Rn-222.
Permeability
The permeability of the soils for gas flow is measured with the apparatus
used to take grab samples of soil gas (Figure 1). Soil gas is withdrawn using
the 1/2 in diameter soil pipe at a measured rate of 200 cc/min. The pressure
differential, P (atmospheric) - P (line), required to maintain the flow is also
measured using either a pressure differential transducer or magnehelic pressure
gauges. The gas flow permeability is then calculated using a relationship
reported in "Review of Existing Instrumentation and Evaluation of Possibilities
for Research and Development of Instrumentation to Determine Future Levels of
Radon at a Proposed'Building Site" by DSMA AtconLtd., January 1983.
k = 2.5 x 10~? |
where Q = 1/min
P '= cm of water
K = cm*
Permeability measurements were generally made at depths of 2' and A'.
Water, bedrock or changes in soil type often caused the permeability to change
considerably with depth.
Sample Collection
In our study samples of soil and soil gas and permeability measurements
38
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were generally taken at depths of 2 and A ft., and at distances of about 1 1/2
ft. and > 20 ft. from the basement wall (Figure 3). To more adequately
characterize the soil as it relates to radon entry into homes; measurements
should be made to depths of 6 ft. when possible. For homes with basements,a
soil depth of 6 ft. would normally be about 1 ft. below the basement floor.
Profiles with sampling at depths of 2, 4, and 6 ft. would more adequately
characterize the soil volume that contributes most to the soil gas radon
entering homes. Samples taken from beneath the basement floor from sumps,
floor drains, wall interiors, etc. relate directly to measurements made in the
soil around the house.
Tracer Studies
A passive perfluorocarbon tracer technique developed at Brookhaven
National Laboratory was used to make in house multizone air infiltration
analyses. Perfluorocarbon tracers were also placed in the soil near homes and
the fraction of emitted gas that entered the house was measured. The tracer
sources were placed in the FVC soil pipes in the same position as the alpha-
track detectors (Figure 2). Tracer gas sources were placed in the PVC soil
pipes located 1 1/2 ft. from the foundation at depths ranging from 2 to 4 ft.
Tests conducted at 45 homes showed that, on average, 55% of the emitted tracer
actually entered the houses. Five different tracer gases are available and
could be placed at various locations in the soil around or under a home to
study the flow of soil gas into homes. These measurements can be integrated
over time period ranging from about 6 hrs to several months.
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
39
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-P-
o
Evacuated Flask
for Sampling Soil Gas
Pressure
Gage
Flow
,Meter
Diaphragm
Pump
Figure 1 Soil probe schematic
-------
SOIL GAS RADON-ALPHA TRACK MEASUREMENTS
SOIL
2-4 ft
|3" DIA PVC PIPEi;i
11/2" DIA PVC PIPE
(retractable)
POLYURETHANE;
IPLUG
ALPHA TRACK
ilill DETECTOR
Figure 2 Detector placement in the soil
-------
>20ft-
N
\
^ 1
iJfeft
,
r /
/
/
r7 r
/ /
/ /
/ /7
/
/
/
t /
/
/ s
**
Soil
1
Figure 3 Locations of soil permeability measurements
-------
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
OVERVIEW OF SELECTING RADON MITIGATION METHODS
Terry Brennan
ED *4 Box 62
Rome, New York 13440
315-865-4269
Over the past several years a growing number of
researchers and contractors have been lowering elevated
radon levels in residences by a number of techniques. All of
them fit into one of the following categories:
1 ) Prevent radon entry
preventing radon entry by soil depressurization
or pressurization
preventing radon entry by basement
pressurization
preventing radon entry by sealing of entries
2) Dilution of radon by introducing outside air
(It is important that this does not increase soil
entry by putting negative pressure on the basement)
heat recovery balanced flow
non-heat recovery flow (Blowing in or powered by
negative pressure on the basement)
There are perhaps a dozen specific methods that have
been tried with varying degrees of success in lowering radon
concentrations and no doubt several more that are
experimental, untried or undreamed of. The advantage to
having a number of techniques available to choose from is
that it gives flexibility - an opportunity to use a method
that has a greater chance of success.
The problem of course is to select the one or two from
amoung the multitude that gives you greater chance of
success or Is most appropriate for the situation.
Here are my thoughts on selecting a mitigation
technique, based on experience, feelings, the work of many
others and of course analysis of the physics involved.
Please keep them in perspective. In many ways they are
Incomplete or tentative. They are certainly open to new
thought and modification. I would be very distressed If they
interfered with new insight or discouraged asking questions
by appearing to provide answers when they are really ideas.
Begin at the House
Probably 80* of the Information I use to decide on a
43
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mitigation technique is gathered by using ray eyes and brain
while visiting the house. First thing I do is see what state
of mind the homeowner is in. I may be the first
semi-knowledgeable person to come in contact with them and
they may have a number of fears concerning their health,
their families health (will this affect my daughter's ability
to have children ?) and the impact on the value of the
property. I want to keep them from undue panic but not calm
them down so much that they don't do something about a real
problem.
The second thing I do is get a feeling for the house by
walking around it keeping my mind clear and paying attention
to ray peripheral vision. I'm looking for how the building's
put together, are there any unaccounted for volumes in the
house, exhaust fans, furnaces, ways to get pipes around. But
most importantly I'm looking for ways that radon can enter
the building, how does the building hit the ground, sumps,
footer drains, crawlspaces, any place there is a large soil
surface that has good airflow connection to the house.
I am always asking "What is going on here ?" Where is
radon coming in ? Why is it coming in at all ?
Then I make a floorplan and fill out the site form.
This is nothing more than a way to get the information most
critical to selection of a mitigation plan together in one
spot. The homeowner may know if there are exterior footer
drains, perhaps there are gutters emptying into risers from
the footer drains and you can see them. The homeowner may
have photographs of the building under construction from
which you can learn a great deal. Once again it is physical
inspection that tells you most.
Look and see !!
The key things I look for when simply observing are:
For soil depressurization
soil gas entry points using eyes and smoke sticks
anything that is like a cavity that has a large
contact with soil surface
hollow core block walls, cored and reinforced ?
interior or exterior footer drains
sump holes (drains or not?)
For basement pressurization
basement that seems tight and Is easily isolated from
the upstairs
no combustion appliances upstairs
basement that is hard to apply soil depressurization
to (finished, hard to seal wall or slab openings)
44
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For dilution with outside air
crawlspace or basement that is easy to isolate
(no freeze problems, few penetrations)
tight house
lack of other options
Measurements
Soil Depressurization Tests
Drill at least two holes through the slab (basement
floor, slab on grade or crawlspace floor). One of these is
1-1/4" diameter (coincidentally the O.D. of the hose for a
Eureka Mighty Mite vacuum cleaner), the other 3/8".
Use smoke sticks to see if soil gas is entering from
the holes (if it is then the make up air must be coming from
somewhere, eh?
Look in the large hole. What do you see ? *2 stone,
sand and gravel, silt, clay, bedrock ? A good bed of stone
everywhere and you can easily depressurize the entire
sub-slab soil surface (maybe 1800 square feet or so in one
fell suction point).If it is clay it will be hard to get any
pressure field to develop under the slab. If the soil has
settled away from the'slab (most likely near the .edge ) you
may have good access to a large soil surface even if the
sub-slab soil is clay.
If the basement wall is concrete block drill at least
one 3/8" hole in it. If there is a wall that has a slab on
grade next to it (like a garage floor, a patio or living
area as in a split level design) then drill a 3*8" hole in
that and one hole in another wall.
Take a grab sample under the slab and in holes in the
block walls (or better yet do a sniff with a scintilation
flask). Are they higher than the basement air ? Are they
higher because it is a major source or because the air under
the slab is very stagnant ? This is one of the tests I'm not
sure how to interpret. Does it really make a difference if I
depressurize the soil in the location with the highest
concentration ? I are sort of using that as a guideline right
now, but I wish someone would do some research to help me
understand grab sample results better.
Use the vacuum cleaner to put a suction on the large
hole in the slab and check with smoke sticks at the other
holes that you've drilled through the slab and walls or at
floor cracks, sump holes and other openings through the slab
that were already present to see how easily air will move
beneath the slab. If there is *2 stone or a cavity under the
slab this will probably be quite far. If it is sand under
the slab you can expect a pressure field to develop only 5
45
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to 15 feet away from the suction point. Sometimes in a very
fine, tightly packed soil (fine sand or silt) you will get
no airflow with this test, but if you release some Freon
under the slab at one of the smaller holes it will quickly
move to the vacuum where it can be detected in the vacuum
exhaust with a halogen detector of the type used by
refrigeration and air conditioning technicians. With the
vacuum cleaner not running you can inject Freon under the
slab and find locations where it leaks back into the
basement, identifying soil gas entry routes, and if
exterior footer drains are present you can sometimes find
where they drain away to daylight by sniffing around outside
and finding Freon exiting to the open air.
The purpose of these tests are to decide whether soil
depressurization can be effectively employed as a mitigation
technique. If it is easy to develop a pressure field in the
sub-slab agregate or block wall then this will be a
preferred method. If the vacuum cleaner test results show no
airflow but Freon will move or if the vacuum cleaner suction
test ios marginal (spotty or only a few feet) then sub-slab
suction might be possible but should be considered with
other possibilities.
Basement Pressurization
A fan door test between the basement and upstairs is
done with particular attention paid to the 10 Pascals or
less delta P range. The test should be run so that air is
being blown from the upstairs into the basement. In the
basement another person is checking with smoke sticks to see
when soil gas stops entering the building, reverses and is
actually leaving the basement and being blown back out into
the soil creating a sort of air pressure shield that forces
soil gas away from and around the building. If this can be
accomplished using a small enough airflow (I'd say less
than 300 cfm at 10 Pascals) then basement pressuriztion may
be considered as a mitigation tehcnique. In this method air
would be drawn from the upstairs house putting some negative
pressure on the upper part of the building and blown into
the basement to pressurize it and prevent soil gas entry.
The fan door test will give you some idea of what
performance characteristics a fan would need to do the job.
If the airflow rate can be lowered from 300 cfm to 200 cfm
by sealing the floor between the basement and the upstairs
then this should not greatly add to the energy load from
Infiltration because it is just reversing the normal stack
effect airflow found in cool climates In the winter time.
Another precondition for this mehtod would be the absence of
* fireplace, woodstove or other vented combustion device in
the upstairs where the pressurization air would be drawn
from.
Dilution of Radon Test
46
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A fan door test is done on the whole house to get an
idea of how tight the building is. This will aid in deciding
if introducing dilution air is a possibilty for controlling
radon levels. Armed with some simple infiltration models and
assuming that dilution air can be added without putting a
negative pressure on the house that would increase soil gas
entry an estimate can be made of the expected reductions in
radon concentrations for varying increases in ventilation
air.
If there is a crawlspace or basement that would be easy
to isolate from Hvingspace and does not contain things that
would need freeze protection (or are easily protected from
freezing) then I would consider isolation of the space and
passive ventilation (followed by active ventilation if
passive didn't quite do it).
Selecting Th» Mitigation Technique
When it comes to selecting a mitigation method I am
currently using the following order of preference.
soil depressurization (or pressurization)
basement pressurization
isolate and ventilate (crawlspace or
basement )
ventilate house
For deciding on what do do within each of these
categories I am using logic shown in the decision charts for
each of these categories at the end of this paper.
All of this is just used as guidelines and the final
selection will involve aesthetics, noise, homeowner
preference, budget, insight from the mitigation contractor,
permanence of installation, power consumption, longevity and
a variety of other more or less subjective factors that may
overide the logic outlined above.
A series of figures that summarize this discussion,
including flow diagram and summary sheets, are supplied
on the pages that follow.
-------
Selecting Mitigation Method
Inuestigate Building by
looking, filling out site forms,
doing qualitatiue and quantitatiue
tests.
Use Results of Tests and
Floujcharts to make a List
of Mitigation Techniques to
be Considered
Make the Final Selection Based
on Vour Current Method Prioritization
List and all Those Important Factors
That Flowcharts Don't Rccomodate
flesthetics, Noise, Homeowner
Preference, Contractor Input,
Combinations of House Features
That the Charts Don't flllouj.
-------
LLlith
Footer
Drains
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mp French
IB Drains
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Footer Bottom |
Drains end Drain*
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k-
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\V ^v^^x^x^'vv\^,'\^^^^.x
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JL. ^_A
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I I
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Large
Entries
T
Sub Slab
Suction
Considered
49
-------
UJalls
Block
Poured Concrete
Or Stone
Sealed or
Scalable
Unseeleble
Greb Samples
I
T
liialls
Closed
RtTop
Seal
Block
Tops
^XXXXVVXXXXXNNNXXVVVVVVNVVNV-
| Block UJall |
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50
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Current Prioritization List
My current order of preference for mitigation
techniques is as follows :
Depressurize soil or isolate and uent non-Iiuing
spaces (use flowcharts for malls and Floors
to find Luhich methods should be considered
for the house)
Pressurize basement (Do a fan pressurization
test on the basement using the basement door
to decide if this is appropriate and if so what
fan flow at what pressure drop is needed.
Currently, I'm using 300 cfm as the decision point)
fidd uentilation air to dilute the radon (Use a fan,
test on the whole house to help decide if adding
dilution air mill prouide the reductions needed
assuming that it can be done with balanced
or positiue pressure flow).
51
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HOUSE ID
NAME
HOUSE SUMMARY SHEET
PHONE NUMBER
ADDRESS
HOUSE TYPE
HOUSE AGE
TIGHTNESS DATA
AIR CHANGES AT 50 PA
EARTH CONTACT AREAS
PIERS
SLAB
CRAWLSPACE
BASEMENT
SOIL GAS ENTHY ROUTES
CRACKS IN WALL
CRACKS IN SLAB
EXPOSED EARTH
OTHER ENTRIES
ELA
SUMP HOLE W/DRAIN TILE
AIR DUCTS UNDER SLAB
OPEN CONCRETE BLOCKS
52
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HOUSE SUMMARY SHEET - PAGE 2
NEGATIVE PRESSURE DATA
Exhaust Devices
Bath Fans
Dryer
Range Fans
Kitchen Fans
Whole House Fan
Heating System Type
Fuel
Thermal Bypasses
Around Chimney
Balloon Walls
Soffits
Attic Scuttle
Other Bypasses
CFM
Distribution
Plunbing Chase
Recessed Lights
Bath Fans
Pocket Doors
RADON MEASUREMENT HISTORY
Time Integrated
Date Location
Results
Units
53
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HOUSE SUMMARY SHEET - PAGE 3
Grab Samples
Date Location Results Units
Suggested Mitigation Strategies:
54
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FLOOR PLAN
HOUSE ID:
HOUSE ID:
FLOOR PLAN
LOCATION:
TECHNICIAN:
DATE:
NOTES:
-------
This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication.
INTERIM REPORT ON DIAGNOSTIC PROCEDURES
FOR RADON CONTROL
B.H. Turk, J. Harrison, R.J. Prill, and R.G. Sextro
Indoor Environment Program
Applied Science Division
Lawrence Berkeley Laboratory
University of California
Berkeley, California 94720
(Editor's Note: The following pages are an abstract of the report, EPA-
600/8-88-084 (NTIS PB88-225115), June 1988, not available at the time
of the Workshop.)
I. INTRODUCTION
With the discovery of high indoor radon (Rn-222) concentrations in a significant
number of residences since the late 1970's, it has become important to develop a better
understanding of the mechanisms of radon movement into and accumulation in
buildings and suitable methods for controlling or eliminating the accumulations. In
general, earlier research has found that the most significant source of indoor radon is
the soil surrounding the building shell from which radon migrates into the building
transported by pressure-driven flow of soil gas. A few of the factors influencing the
radon entry rate include indoor-outdoor air temperature differences, wind loading, soil
characteristics, construction details of the building superstructure and substructure, and
coupling between the soil and the substructure.
In order to further investigate radon entry and radon control techniques, the U.S.
Environmental Protection Agency (EPA), the Department of Energy (DOE), and the
New Jersey Department of Environmental Protection (NJDEP) are funding an intensive
study in fourteen northern New Jersey homes. The research is being conducted by the
Lawrence Berkeley Laboratory (LBL) in seven homes and collaboratively by Oak
Riclge National Laboratory and Princeton University in a second set of seven homes.
Since few studies have attempted to relate influencing factors to entry rates and to
investigate the importance of these factors on systems designed for radon abatement,
th; fc!!cv,-;r.- overall objectives were established for this project.
Extend our understanding of the fundamentals of soil gas flow and radon entry
into buildings and improve our basic knowledge of factors that influence the entry
rate.
Develop a better understanding of the success or failure of certain mitigation
techniques and of the operational ranges of key parameters that affect the utility of
these techniques.
Refine and develop analysis procedures for diagnosing radon entry mechanisms and
the selection of appropriate control systems.
The basic research plan for this project has four main operational components: 1)
house and site characterization measurements, 2) baseline and continuous monitoring of
environmental and building parameters, 3) diagnostic procedure development, and 4)
installation and operation of selected mitigation techniques.
56
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This report focuses primarily on item 3, development of diagnostic procedures.
Diagnostic procedures are defined here as an organized and logical set of
measurements, tests, and observations that are necessary for identifying the specific
means by which radon enters and accumulates in a particular structure. In addition,
these procedures should point the way to a suitable system or technique for controlling
the indoor radon levels. These procedures may also encompass follow-up
measurements, tests, and observations important in optimizing mitigation system
performance. This development effort builds on the previous, on-going, and generally-
unpublished work of others, including Scott, Tappan, Henschel, Ericson, and Brennan.
as well as on the basic scientific understanding developed by Nazaroff, Nero, and
others at LBL. Hopefully, it provides a format for refinement, reduction and
interpretation of the measurements and observations necessary for selecting an
appropriately designed, effective, and economical system for controlling indoor radon
levels in a majority of existing U.S. single-family houses with elevated radon
concentrations.
TABLE I: Project Measurement Activities
I) Parameters to be monitored continuously:
indoor radon concentrations (various locations within the house), and possibly
radon progeny concentrations (smaller subset of houses),
outdoor and indoor temperatures,
meteorological parameters at each site, including wir.dspeed and direction,
pressure differentials across ths building shell (various locations),
soil moisture and temperature, and
barometric pressure and precipitation at one central site.
2) Parameters to be monitored periodically:
soil air permeability,,
ventilation rate,
indoor water vapor,
soil gas radon concentrations at selected locations, and
occupant effects and activities, including operation of a fireplace or wood
stove, forced air furnace systems, exhaust fans, etc.
3) Parameters to be measured once or occasionally:
effective leakage area,
radon progeny concentrations.
soil characteristics (at LBL), including permeability, grain size distribution, soil
radium concentration, and emanation ratio,
frost depth and snow cover,
pressure-field mapping to determine coupling between building shell and
surrounding soil,
iracer gas (SF.) injection in soil and resulting concentrations within the
building shell (if utilized), and
additional parameters specific to the mitigation technique under investigation,
such as the.flc.*' rate of air through a block wall or subslab ventilation system,
or tracer gas analysis of flow pathways.
57
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II. OUTLINE OF GENERAL DIAGNOSTIC PROCEDURES
The premise for much of the diagnostic procedures developed and discussed here is
that the pressure-driven flow of radon-bearing soil gas is the most significant source of
radon in houses with elevated concentrations. While further discussion of this premise
is-beyond the scope of this report, the reader should refer to DSMA, (1985) and
Nazaroff, et a/., (1985a, 1985b, 1986) for additional discussion. On the other hand,
other potential sources of radon, such as water and building materials, are also included
in the diagnostic procedures discussed here. A good overall review is found in Nero
and Nazaroff, (1984).
The procedures described here rely on a series of individual site-specific
observations and measurements of air flow, pressure differentials, radon concentrations
and near-building material characteristics. This collection of measurements is then
used to identify primary radon sources (water, building materials, soil) and most
probable radon entry points and mechanisms. Various tools and instruments (see Table
2) are necessary to conduct the diagnostic procedures discussed here and this report
assumes that the reader has prior experience with flow and pressure measuring devices,
and alpha particle counting techniques. Samples of forms for recording this diagnostic
information are found in Appendices A, B, C, D and are referred to in the text.
Some investigators have used gamma radiation surveys as a method of locating
radon source materials. Making and interpreting results of such surveys in buildings
appears to pose a number of difficulties and we have not utilized this technique here.
Since soil gas flows are the most significant source of radon in houses, the location and
extent of penetrations through the building shell, along with physical characteristics of
the surrounding soil (such as air permeability) are the most important determinants of
radon entry and source locatoin. Variations of apparent radium and/or radon
concentration in the soil near the building may not be correlated with entry locations.
The methods we discuss here, particularly air sampling for radon at suspected entry
points and in areas where radon accumulation is likely, provides a more direct method
of identifying radon sources and entry locations.
Radon, not radon progeny, is measured before, during, and after diagnostics and is
the contaminant on which control efforts are focussed. In its role as progenitor,
control of radon also controls radon decay products, which are responsible for the
adverse health risks associated with radon exposures. There are some potential
mitigation measures directed at progeny control only, such as air cleaning. These are
not considered here.
Before diagnostic procedures for radon control are employed, the indoor radon
concentrations on any occupied floor in a particular structure should be verified during
the heating seasons as being greater than the recognized guideline. Methods and
procedures for determining indoor radon concentrations during non-heating season
periods are being studied. However, relationships between heating season and non-
heating season concentrations in homes with elevated concentrations have not been
established. In this report, EPA's suggested guideline of 4 pCi/L annual-average
concentration is used as a conservative heating season worst case target in diagnosis and
in determination of successful mitigation. Ultimately, these heating season
measurements would predict the annual average concentration. However, at this time,
we are unable to make that prediction. The basic procedure here can be used with
different guidelines. For example, in an area with many homes with indoor
concentrations greater than 20 pCi/L, these houses might be the main objective of
diagnostic and remedial efforts during the next several years.
58
-------
TABLE 2: Instruments and Equipment
Radon Grab Sampling:
Alpha scintillation calls
Portable photomultiplier tube counting station
Band pump with sample tube and 0.8 iaa filter
Compresaed air or nitrogen for cell flushing
Vacuum pump for evacuating cells (70 cm, 27 in. Hg vacuum)
Air Leakage and Flow
Measurements:
Calibrated-flow blower door (6800 m3h"1, 4000 cfm 9 5 Pa)
Pitot tubes (electronic or liquid-filled manometers: 1-50 kPa)
Hot wire anemometer (with temperature sensing element)
Smoke tubes
Industrial vacuum cleaner (170 m h ,
1.5 m (5 ft.) flow sections of :
Non-toxic tracer gas (SF
D
100 cfm 8 2m, 80 in. H_0 pressure)
7.5 em (3 in.) PVC with coupler
15 cm (6 in.) galvanized duct
Freon 12)
Tracer gas detection instrument
Soils Characterization:
Soil core and auger samplers
3/4" reversible electric drill
Soil air permeability device
Sliding hammers
Various diameter drill bits, including some
attached 1.5 m (5 ft.) long extensions
1.5m (5 ft.) long probe pipes
Inspection Equipment:
Stiff wires
Telescoping mirrors
Portable gama spectrometer
Fiber optics scope
Tools:
3/8" variable speed hand drill
Masonry bits
1/2" hammer drill
Impact bit*
Pocket flashlights
Band sledge
Pry bar
Pipe wrench
Locking pliers
Adjustable wrenches
Portable lights
Step ladders
Long blade screwdriver
Miscellaneous:
Forms
Inspection hole plugs
Epoxy-based mortar patch or hydraulic cement
Duct tape
Duct leal
0.3. 0.8. 1 cm (1/8, 1/4, 3/8 in.) diameter tubing
Various-sized hypodermic needles
Plastic film
Thermometers: electronic and mercury-filled glass
Silicons sealant
59
-------
III. DISCUSSION OF DETAILED DIAGNOSTIC PROCEDURES
A "General Plan for Radon Control", shown in Figure I, outlines the basic process
for mitigating elevated radon levels. Once a. structure is determined to have a radon
problem, a survey of the structure is conducted that characterizes soil-linked radon
entry points in the building shell and evaluates potential non-soil sources. After
reviewing the results of the diagnostic measurements, suitable options for radon
mitigation are considered and a final plan for the control system(s) is developed.
Follow-up measurements of indoor air concentrations and system operating conditions
are made once the installations are completed. If follow-up short-term diagnostic
measurements of indoor radon concentrations are still greater than the guideline, then
modifications or additional system options must be installed. For apparently successful
installations, the system is tuned for improved efficiency (i.e., effective performance
with reduction in system size requirements) and more economical operation and the
reduced indoor levels are verified with a 14-day average heating season measurement.
The report discusses details of the various diagnostic methods, techniques, and
procedures currently under development. Figures 2-7 in flowchart-graphical form
show a logical sequence of steps that will assist in guiding the reader through the
measurement and evaluation process. We emphasize again that this system of diagnosis
is for research purposes and is intended to serve as the basis of somewhat simpler
approaches for general application.
IV. SUMMARY
A preliminary set of diagnostic procedures has been developed for identifying the
sources of indoor radon problems and selecting systems for controlling radon. In the
homes where the recommended remedial measures have been installed, based on the.
diagnostic measurements, radon concentrations have fallen below the guideline of 4
pCi/L. However, a rigorous process for selecting successful, optimized systems has not
yet been developed for widespread use by technicians and contractors.
Three new, and largely unvalidated, techniques are presented that may assist in
determining the contributions to indoor radon levels from the domestic water supply
and building materials and the approximate distribution of air infiltration leakage area
in a structure. This document reports progress in research still underway. Additional
data and observations are being made that may support, augment, or in some cases
invalidate, some of the conclusions discussed here.
Other diagnostic techniques and tools under investigation in this and other studies
include: use of tracer gases to quantify entrainment of building air into subsurface
ventilation systems; creating flow and pressure maps for hollow block foundation walls;
attempting to quantify and apportion subsurface ventilation from below slabs and from
within block walls; estimating outside air ventilation that enters along the soil/house
line; and development of a radon "sniffer" with faster recovery time between samples
taken from test holes, entry points, and indoor air. Another new method will attempt
to challenge an installed mitigation system by using a depressurization fan to gradually
increase substructure depressurization and thereby determine the system failure point.
This work is cofunded by the U.S. Department of Energy (DOE) and by the US
Environmental Protection Agency (EPA). DOE support was from the Assistant
Secretary for Conservation and Renewable Energy, Office of Building and Community
Systems, Building Systems Division, and from the Director. Ofice of Energy Research",
Office of Health and Environmental Research, Pollutant Characterization and Safety
Research Division under Contract No. DE-AC03-76SF00098. EPA support, und-r
Interagency Agreement No. DW8993 IS76-01-0 with DOE, was through the Office of
Environmental Engineering Technology Demonstration, Office of Research and
Development.
60
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V. REFERENCES
Becker, A.P. and Lachajczyk, T.M., (1984), Evaluation of Waterborne Radon Impact on
Indoor Air Quality and Assessment of Control Options, Report EPA-600/7-84-093
(Springfield, VA: NTIS).
DSMA ACRES, (1979), Report on Investigation and Implementation of Remedial
Measures for the Radiation Reduction and Radioactive Decontamination of Elliot
Lake, Ontario, Dilworth, Secord, Meagher, and Associates, Limited and ACRES
Consulting Services Limited, (Ottawa, Canada: Atomic Energy Control Board).
DSMA ACRES, (1980), Report on Investigation and Implementation of Remedial
Measures for the Radiation Reduction and Radioactive Decontamination of Elliot
Lake, Ontario. Dilworth, Secord, Meagher, and Associates, Limited and ACRES
Consulting Services Limited, (Ottawa, Canada: Atomic Energy Control Board).
DSMA Atcon Ltd., (1983), Review of Existing Instrumentation and Evaluation of
Possibilities for Research and Development of Instrumentation to Determine Future
Levels of Radon at a Proposed Building Site, Report INFO-0096, (Ottawa, Canada:
Atomic Energy Control Board).
DSMA Atcon Ltd., (1985), A Computer Study of Soil Gas Movement into Buildings,
Report 1389/1333, (Ottawa, Canada: Department of Health and Welfare).
Environmental Protection Agency (EPA), (1986a), Interim Protocols for Screening and
Followup Radon and Radon Decay Product Measurements, Office of Radiation
Programs, Report EPA 520/1-86-014 (Washington, DC: US EPA).
Environmental Protection Agency (EPA), (1986b), Radon Reduction Techniques for
Detached Houses, Air and Energy Engineering Research Lab, Report EPA 625/5-
86-019 (Research Triangle Park, NC: USEPA).
Ericson, S.O., Schmied, H., and Clavensjo, B., (1984), "Modified Technology in New
Constructions, and Cost Effective Remedial Action in Existing Structures, to
Prevent Infiltration of Soil Gas Carrying Radon", in Indoor Air, Proceedings of the
3rd International Conference on Indoor Air Quality and Climate, Vol 5, pp. 153-
158, (Stockholm: Swedish Council for Building Research).
Fisk, W.J., (1986), "Research Review: Indoor Air Quality Techniques", Report LBL-
21557 and in Proceedings of IAQ '86, Managing Indoor Air for Health and Energy
Conservation, pp. 568-583 (Atlanta, GA: ASHRAE).
Gesell, T.F. and Prichard, H.M., (1980), "The Contribution of Radon in Tap Water to
Indoor Radon Concentrations", in Proceedings of the Symposium on the Natural
Radiation Environment III, Vol 2, U.S. Department of Energy, CONF-780422, pp.
1347-1363, (Springfield, VA: NTIS).
Henschel, D.B., and Scott, A.G., (1986), "The EPA Program to Demonstrate Mitigation
Measures for Indoor Radon: Initial Results", in Indoor Radon, Proceedings of an
APCA International Specialty Conference, pp. 110-121, (Pittsburgh, PA: Air
Pollution Control Association).
Nazaroff, W.W., Boegel, M.L., Hollowell, C.D., and Roseme, G.D., (1981), "The Use of
Mechanical Ventilation with Heat Recovery for Controlling Radon and Radon
Daughter Concentrations in Houses", Atmospheric Environment, 15, pp. 263-270.
61
-------
Nazaroff, W.W., Feustel, H., Nero, A.V., Revzan, K.L., Grimsrud, D.T., Essling,
M.A., and Toohey, R.E., (1985a), "Radon Transport into a Detached One-story
House with a Basement", Atmospheric Environment, 19, pp. 31-46.
Nazaroff, W.W., Lewis, S.R., Doyle, S.M., Moed, B.A., and Nero, A.V., (1985b).
"Experiments on Pollutant Transport from Soil into Residential Buildings by
Pressure-Driven Air Flow", Report LBL-18374, Lawrence Berkeley Laboratory, to
be published in Environmental Science and Technology.
Nazaroff, W.W., Doyle, S.M., Nero, A.V., and Sextro, R.G., (1985c), "Potable Water as
a Source of Airborne Radon-222 in U.S. Dwellings: A Review and Assessment",
Report LBL-18154, Lawrence Berkeley Laboratory, to be published in Health
Physics.
Nazaroff, W.W., Moed, B.A., Sextro, R.G., Revzan, K.L., and Nero, A.V., (1986),
Factors Influencing Soil as a Source of Indoor Radon: A Framework for
Geographically Assessing Radon Source Potentials, Report LBL-20645, Lawrence
Berkeley Laboratory, Berkeley, CA.
Nero, A.V., and Nazaroff, W.W., (1984), "Characterising the Source of Radon Indoors",
Radiation Protection Dosimetry 7, pp. 23-29.
Nitschke, LA., Traynor, G.W., Wadach, J.B., Clarkin, M.E., and Clarke, W.A., (1985),
Indoor Air Quality. Infiltration and Ventilation in Residential Buildings, W.S.
Fleming and Associates, NYSERDA Report 85-10, (Albany, NY: New York State
Energy Research and Development Authority).
Sachs, H.M. and Hernandez, T.L., (1984), "Residential Radon Control by Subslab
Ventilation", in Proceedings of the 77th Annual Air Pollution Control Association
Meeting, San Francisco, CA, Paper No. 84-35.4, (Pittsburgh, PA: Air Pollution
Control Association).
Scott, A.G. and Findlay, W.O., (1983), Demonstration of Remedial Techniques Against
Radon in Houses on Florida Phosphate Lands, Report EPA 520/5-83-009,
(Springfield VA: NTIS).
Sherman, M.H. and Grimsrud, D.T., (1980), "Measurement of Infiltration Using Fan
Pressurization and Weather Data", Report LBL-10852 and in Proceedings of First
Air Infiltration Centre Conference on Air Infiltration Instrumentation and Measuring
Techniques, pp. 277-322 (Berkshire, UK: Air Infiltration Centre).
Tuma, J.J., and Abdel-Hady, M., (1973), Engineering Soil Mechanics, p. 102,
(Englewood Cliffs, NJ: Prentice-Hall).
Turk, B.H., Prill, R.J., Fisk, W.J., Grimsrud, D.T., Moed, B.A., and Sextro, R.G.,
(1986), "Radon and Remedial Action in Spokane River Valley Residences", Report
LBL-21399 and in Proceedings of 79th Annual Meeting of the Air Pollution Control
Association, Minneapolis, MN, Paper No. 86-43.2 (Pittsburgh, PA: Air Pollution
Control Association).
62
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Figure 1
General Plan for Radon Control
Problem Diagnosis
Measure heating season indoor radon concentrations
Evaluate non-soil sources
Characterize structure and soils and identify entry points
Selection and Implementation of Mitigation Systems
- Consider results of diagnostic measurements
Review options for mitigation
Develop and implement mitigation plan
Post-Mitigation Evaluation
Monitor indoor air concentrations
Measure mitigation system operating parameters
Successful
(improve system efficiency)
Unsuccessful
modify system
or
install additional options
XBL 871-8920
63
-------
Figure 2
Problem Diagnosis
Replicated, 7-Day Average Radon Concentration in Indoor Air
Heating Season Measurements
Levels < 4 pCl/L on all livable HOCKS - No Action
~l
Levels > 4 pCi/L on any livable floor
\
Conduci Building Survey
L
Figure 2A
Non-Soil Sources
Characterize Structure and Identity Entry Points
i.) Conduct Visual Inspection:
- Complete forms (sue and lloor plans, elevations, housing surveys, occupant questionnaire)
- Probe likely entry points (wail or lloor cracks and holes, masonry interlace, block wall lop and holes) using shit wiie.
screwdriver, and smoke lubes.
2.) Grab Sample Indoor Air under Natural Conditions
Collect alpha scintillation cell grab samples under existing natural conditions Irom each unique building tone (garage. 2nd lloor.
1st lloor. basement, crawlspace. slab-on-grade areas).
3.) Grab Sample Indoor Air under Mechanical Depressuriiation
Collect grab samples using alpha scintillation cells Irom likely entry points and various building tones (this sampling could be
repeated 2-3 days alter the lirst sampling to document the variability in the technique due to environmental (actors or sampling
procedure)
Depresaunie house using blower door to -10 Pa in substructure lor > 30 mm. (may not cause representative distnbution of Rn
throughout house)
a) grab sample ol indoor air from each separately delined room or zone at mid-height
b)grao sample from cavities m bottom course ol blocks, approx. every 3 m (10 fl.) (through existing or 0.6 cm (1/4 in.) drilled
inspection holes - lit! holes on completion)
grab sample Irom 2 to 4 holes through slab (through existing or 1 cm (3/8 m.) drilled inspection holes)
C) grab sample Irom behind lined walls every 3 m (10 It.) (Approx IS cm (6 m.) above lloor)
d) grab sample Irom each obvious penetration to soil (condensate drains, lloor drams, sumps, service penetrations, toilet and
snower bases)
e) grab sample Irom wall/door joints Irom each wall (where accessible)
I) grab sample Irom representative wall and lloor cracks and French drain cavities
For el and 0. either:
1) Tape over joint, crack or French dram lor approximately 60 cm (2 It.) to either side ol sample location and seal ends m
French dram, or
2) Tapo or seal with sealant, plastic film over |Oini/crack. evacuate Irom beneath film, ana allow film »paca to charge with soil
gfts b«lor« collecting »«mpl«.
-------
h| grab sample from other confined space in contact witti in* wills or now. sucn as framed will cavities
Count the activity lor eicfi simple (see tent) and identify on hou>« lloor plan. Samples with concentrations < room concentration
are not likely entry points, those with concentrations 2-3 X room concentration are possible entry point], and those witrt concen-
trations > 3 X room concentration are likely entry points.
4.) Qualify Air Movement From Likely Entry Point*:
Depressunte nouu to 30 Pa in tub structure to chanctenie air movement Irom soil to house through entry points using
Chemical smoke
Check flow ah substructure cracks, holes or joints in slabs or walls
lops ol biock wails
previously drilled test holes
between floors
exterior soil line
other potential entry points: sumps, drains, shower and toilet bases, service entrances and penetrations
5.) Conduct Blower Doof Test! to:
- meiiure me equivalent leakage area of:
tne whole house
substructure only
superstructure only
- identify large notes and bypasses between upper floors and basements that will ennance the SUCK effect
8.) Observe Ventilation Communication Within Block Wills and Beneath Slabs:
- using nign vacuum (2 m: SO in. water) and hign flow (170 m'tr1; 100 ctm) blower, depressunze subslab region and measure
pressure drops and determine e!r movement at likely entry points and drilled test holes, including those m wills
- attach blower to block walls and check for air leaks in the walls and the eitent ol Ihe induced ventilation at cracks and holes
and drilled ten holes.
7.) Observe Effect ol Appliance Operation:
- using micromanometer determine additional depressuntation of substructure due to appiTince opereiion (dryer, rurnice imoil-
ance. fireplace, wood stove. e»hausl fan) by cycling appliance on/off for appro>. 20 cycles.
Additional depressunzatlon > S Pa
Take corrective action
Additional deprenurizalion < 5 Pa
I
~~~-~~ No jcnon
8) Conduct Soil Tetts (optional):
- i* Subsurface or weeping 1iie ventilation may be considered as mitigation options conduct neif.nouse jo'il a'lf permeiailtry
nil. and so'ii Ri test
XBL
B9I9
-------
Figure 3
Radon in Water
Local Well Water?
i
INU
X
To
jure
~-~*
i ea
\ Direct Test water
4J method I
\
Water sample analysis
1
Alternative
method
\
Bath air gn
Cw < 40,000 pCi/L
No water
treatment necessary
Cw > 40,000 pCi/L
(replicated)
Operate Bath Shower 15 Minutes
to Obtain Closed Room Air Sample
\
__ (Cfinal bath ~ ^initial bath) X ^bath (U
" * Fshower(L/hr) X 0.9 X t(hr)
*+ Cw < 40,000 pCi/L
C > 40,000 pCi/L *
Mitigation options:
- Aerate
- Filter
- Options: 10
I 11
14-day average indoor
radon concentration measurement
I
Indoor levels > 4 pCi/L
Indoor levels < 4 pCi/L
No additional corrective action
Annual follow-up water tests by occupant
Periodic system maintenance by occupant
XBL871-8917
65
-------
Figure 4
Radon Flux from Building Materials
Unusual construction features incorporating local geological formations (rock outcropping) or
large amounts of earth-based construction materials (thermal mass, native stone surfaces)?
No
Yes
i
Measure Rn flux
Flux rate (pCi/m2-hr) X material area (m2)
house*
V, (L)
<2 pCi/L-hr
>2 pCi/L-hr
No materials
mitigation action
necessary
Mitigation options:
- Remove or seal material
- Options: 10
11
Materials mitigation
implemented
14-day average indoor
radon concentration measurement
Indoor levels > 4 pCi/L
and flux <2 pCi/L - hr.
Indoor levels > 4 pCi/L
and flux > 2 pCi/L-hr
I
Indoor levels < 4 pCi/L - No additional action
Annual long-term follow-up indoor air measure-
ments using «-track film by occupant
Periodic mitigation system maintenance by occu-
pant
XBL 871-8918
-------
Figure 5
Selection of Mitigation Systems
Alter a careful review ol Ihe subslruclure(s). ilomizalion ol potential entry points, grab sample and air (low
mapping, and occupant comments on operation ol certain appliances, a mitigation plan should be developed.
It should address control ol radon lor each house starling with one substructure type bolore moving lo Ihe
next substructure type. Crawlspaces (il they exist) are typically Ihe simplest lype to mitigate and work should
begin here il Ihe diagnosis so indicates.
Crawlspace
r
No
Other predominant substructure
types or combinations
Basement With Poured Foundation Walls
As indicated by mapping and inspection survey.
Mitigation options: 1
2
3
4
5
Basement With Block Foundation Walls
As indicated by mapping and inspection survey,
Mitigation options: 1 6 11
1
Yes
Slab on Grade
As indicated by mapping and inspection survey.
Mitigation options:
4 In addition, subslab heating system ducting may require
sealing Irom occupied spaces and rerouting through attic.
5 In addition, subslab heating system ducting may require
sealing from occupied space and rerouting through attic.
7
10
Crawlspace concentration <
0.75 x occupied space - and less
than other substructure zone con-
centrations
Crawlspace concentration ~»
0.75 x occupied space concentra-
tion or greater than other sub-
structure zone concentrations
I
Install 0.09 m1 (1 It1) uniformly distributed venti-
lation/9 m* (100 ft2) floor area or install Ian sized
lor 5 ACH to overpressurize lo -10 Pa. Install
thermal insulation. Seal between Crawlspace
and structure, including return air ducts.
I
14-day average indoor radon concentration
measurement
Indoor levels > 4 pCi/L
- Additional mitigation
1
Indoor levels < 4 pCi/l - No additional action
Annual long-term follow-up indoor air measure-
ments using ii-lrack film by occupant
Periodic mitigation system maintenance by occu-
pant
XBLBM 8915
-------
Figure 6
Mitigation Options
1) Sump sealing - active and inactive sumps
2) Floor drain sealing - if not water-trapped
3) a) Sump sealing and ventilation - active or inactive sumps with or without drain tile
b) French drain sealing and ventilation
4) Subsurface ventilation
A) Exterior B) Interior
If homeowner prefers exterior Gravel under floor slab
No landscaping interference Central ventilation point
No utilities interference every 45 m2 (500 ft2)
Perimeter wall entry points No gravel
Locate near entry points
Exhaust ventilation - soil impermeable, soil Ra high
Supply ventilation - soil permeable, soil Ra low
Drill series of small inspection holes in floor (1 cm; 3/8 in. diam.) and walls (0.6 cm: 1/4 in. diam.) to
determine extent of pressure field.
5) Weeping tile ventilation Where tile is accessible
Where tile is proximate to entry points
6) Wall ventilation - only if sealing successfully limits fan size to < 500 m3rr' (300 cfm) (smoke tubes at
inspection holes to verify extent of ventilation)
7) Floor crack sealing Where majority of cracks accessible
Where cracks localized - no network of cracks
Floating slab gap if no indication of water entry
8) Wall cracks and hole sealing Where majority of openings are accessible
Where openings are localized
Only if blocks are open cell
9) Basement overpressurization (special option)
Where leakage of basement membrane is small
Where sealing of exterior and interior membranes is possible
Where if heating system is forced air, ductwork is tight and no forced air furnace
registers present in basement
Where 1st floor vented combustion devices are not present
Use blower door on basement to estimate approximate fan size: should be < 1 ACH delivery to achieve
5 Pa over-pressure
10) Balanced ventilation with heat recovery (special option)
Multiple substructures:
If indoor concentrations > 4 pCi/L, < 20 pCi/L on all floors:
- Ventilate all floors with 5 X original ventilation to < 2 ACH (new total)
Basement only:
If basement concentrations < 80 pCi/L
- Ventilate only basement where original basement ventilation < 0.2 ACH to new total < 3.5 ACH
System must be installed to match existing finish
11) Balanced ventilation w/out heat recovery (special option)
Unoccupied basements sealed and thermally insulated from occupied space.
In basement install 0.09 m2 (1 ft2) uniformly distributed vents to the outside per 4.6 m2 (50 ft2) floor area
or install fan sized to 5 ACH to overpressurize substructure to 10 Pa
Options not considered here : Coatings
Soil removal
Air cleaning
68
-------
Figure 7
Post-Mitigation Evaluation
Measure: Temperatures and differential pressures in installed ducts, pipes: soil and building interior air (lows
developed by fans in ducts and pipes; radon concentrations in exhaust air streams.
Observe: Integrity of sealants, fillers, and bonding agents. Noise and vibration of fans and blowers. Inspect
for leaks and bypasses in all systems. Correct if necessary.
Repeat grab sample mapping survey and measure average indoor air concentrations for minimum of two
days. ,
Indoor levels > 2 < 4 pCi/L
14-day average radon measurement in
indoor air (heating season measurement)
Indoor levels < 2 pCi/L
Refine system operation until room air
concentrations just begin to show an increase-
then boost system operating parameters
Indoor levels > 4 pCi/L
Grab samples < indoor
(room) concentration *-
Grab samples remain > indoor (room) concentration (and
pressure held is insufficient at likely entry points
mitigation options 3. 4, 5, 6. 9)
Indoor levels ;> 2 < 4 pCi/L - No turlher action
Annual long-term follow-up indoor air measurements
by occupant (..-track film)
Periodic mitigation system maintenance by occupant
Reduce Blower Flows Approx. 50%
Mitigation options:
3 9
4 tO
5 II
6
Increase pressure developed
by blower npprox. 50%
Install additional ventilation
points near remaining entry points
Increase blower flow rates
Mitigation options: 10 f"
See
Dlock-off Subsurface
Ventilation Points
Mitigation options
4
6
4
5
6
9
See
Figure 6
4
5
6
See
Figure 6
i
Figure 6
J
xni n?i Ron,
-------
Figure 8
Distribution of Structure Effective Leakage Areas
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Substructure (ELAb) = d + e + f + g
Substructure ceiling (ELAC) = d
Substructure walls/floor (ELAf) = e + f + g
XBL871 8921
70
-------
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-------
GUARANTEED RADON REMEDIATION THROUGH SIMPLIFIED DIAGNOSTICS
David Saum and Marc Messing
INFILTEC Radon Control services
P.O. Box 1533
Falls Church, VA 22041
l.Q INTRODUCTION
How can guaranteed radon remediation performance be provided at a
price that homeowners are willing to pay? The paper summarizes the
diagnostic procedures developed by INFILTEC to achieve this goal.
Assumptions will be pointed out, as well as problems and questions.
INFILTEC is submitting a patent on the pressure/flow test equipment
and techniques described in this paper.
2.0 TIME/COST
The customer seems to be willing to pay for diagnostics if it will
result in a better system installation with a higher level of
confidence in the remediation. Two to three hours of diagnostics may
be an upper limit on time, with a corresponding cost of $200 to $300.
3.0 RADON SOURCE MAPPING
The radon source is assumed to be primarily under the slab ar.d at
levels 10 to 1000 times the levels in the air. Walls, whether block
or concrete are assumed to not be a problem unless the source mapping
does not show any significant levels. Source mapping consists of
drilling approximately 5 small holes (one at each corner and cne in
the center) and counting a Lucas cell for 5 one minute intervals while
puir.ping subslab air through the cell. The cell is allowed to clear
for two or three minutes between holes. If wide deviations in levels
are noted, or the slab is complex in shape, or the slab is large, then
more holes may be drilled and tested. Although the radon counts do
not allow for daughter equilibrium, the relative levels around the
slab are of most interest and the actual levels are assumed to be 1.5
to 2 tines as high as the count indicates. The combined time for
drilling the holes and counting is approximately one hour. When the
source mapping is completed, the slab areas of most interest (highest
radon) should be known. Drains, sumps, and crawl spaces are also
tested similarly. Walls are only tested if the subslab levels seem
too low to account for the previous screening and confirmation
measurements by the homeowner.
4.0 PRIMARY REMEDIATION TECHNIQUE
Sub-slab suction is assumed to be the primary radon source
remediation technique which should be attemped if at all possible.
Radon is assumed to be prevented from entering the house if there is
an adequate pressure barrier at the slab. Wall suction has not been
found to be necessary in any houses. Some houses have been
encountered that have not been remediated yet, due to complex
construction that makes sub-slab suction difficult.
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
72
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5.0 SUB-SLAB PRESSURE/FLOW MAPPING
A portable suction system with flow and pressure gauges (blower floor)
is installed in a 1" diameter drilled hole or a sump hole that is near
to the radon concentrations and is also near a good venting location.
Selection of a good suction point involves many cosmetic, venting,
radon source, and customer considerations. The fan for the suction
system is outside to avoid worker exposure to high radon
concentrations, and a long flexible tube is used to connect the fan to
the suction hole. Note that apha-track measurements taken during
months of almost daily diagnostic and remedial work, show radon
exposures below 4 pCi/1. Two types of measurements are made: flow
versus pressure in the hole, and pressure in the suction hole versus
pressure in the test holes around the slab. If there is no pressure
induced in the test holes by the suction hole pressure, other suction
holes may be drilled on the assumption that the suction hole was in a
dead spot. If the suction hole pressure induces large pressures at
the perimeter test holes, then the flow has been shown to be good, and
tight enough to induce pressure with standard fans. Cases of marginal
pressure and flow require further analysis.
6.0 EDGE PRESSURE RULE OF THUMB
Simple rules of thumb are assumed to determine the minimum adequate
pressure across the slab. Houses are assumed to be so leaky that
stack pressure is the dominant cause of suction on the slab. The
neutral pressure point is assumed to be in the attic, and the stack
maximum stack pressure on the slab is assumed to be approximately
0.001" WC per foot of building height. This leads to an approximate
rule of thumb of 0.015" WC of suction for the design pressure in a
typical house. This is the worst case pressure to be exerted across
the slab. Actual measurement of stack and appliance induced pressure
are complicated and do not seem to be necessary in most cases.
7.0 ESTIMATING SYSTEM PERFORMANCE
When marginal flow and pressure measurments are encountered, the
capability of a particular fan/pipe system to achieve adequate edge
pressure can be calculated from measured pressure and flow data.
Section 11 of this paper gives a sample of this type of calculation.
It allows tradeoffs to be made between fan sizes, pipe, venting, etc.
8.0 QUALITY CONTROL
The installed sub-slab system must be carefully checked to determine
if it actually achieves the required pressure field across the slab
and whether is has leaks that could cause radon inflow back into the
house. A separate quality control visit is made after the system has
been operating for a least 24 hours. A pressure gauge is
permanently installed on all remediation systems to allow contractor
and the homeowner to quickly verify proper fan operation. Freon is
injected into the system while the fan is on and a freon leak detector
is used to detect leaks in the fan, pipe and vent location. Radon
grab samples are taken to measure remediation performance and the
homeowner is given charcoal and alpha-track test kits.
73
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9.0 INFILTEC RADON REMEDIATION PERFORMANCE
LOCATION
Mt. Airy
Herndon
Owings Mills
Potomac
Potomac
Damascus
Damascus
Mt. Airy
W. Bethesda
Columbia
Potomac
Columbia
Columbia
Columbia
Reston
Germantown
Laytonsville
Herndon
Bethesda
Damascus
Silver Spring
Owings Mills
TYPE OF HOUSE BEFORE REMEDIATION
Split Level
Colonial
Ranch
Split Level
Colonial
Ranch
Ranch
Colonial
Modern
Colonial
Modern
Colonial
Colonial
Ranch
Townhouse
Colonial
Ranch
Colonial
Ranch
Ranch
Ranch
Modern
100 pCi/1
30
26
215
7
11
45
22
67
62
20
59
16
11
150
40
160
12
17
18
12
44
AFTER REMEDIATION
3.3 pCi/1
3.1
1.6
1.6
2.0
1.4
2.0
1.3
4.5*
3.1
0.5
1.3
1.6
1.3
1.6
0.6
1.2
0.8
2.0
1.4
0.2
1.8
The readings before remediation may be summer or winter charcoal
tests in the basement, but the readings after remediation are all
winter charcoal tests in the basement.
* reading after 1st stage remediation on house with slab on rock.
10.0 EQUIPMENT REQUIRED FOR DIAGNOSTICS
Very few remediation contractors are now willing to buy the full range
of equipment that these diagnostics require.
* Continuous Radon Monitor ($3500-54500)
* Rotary Hammer and other tools ($300-$600)
* Pressure Gauge (Analog model $60, Digital model $600-$1400)
* Blower Floor (Analog model: $2500?, Digital model: $5000?)
* Freon Leak Detector and Freon ($150-$250)
TOTAL COST RANGE: $6500 to $12000
74
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11.0 SAMPLE SUBSLAB PERFORMANCE CALCULATION
The objective of this calculation is to predict the pressure that will
be induced under the slab by specific fan and pipe configuration. The
calculation requires formulas for the pressure/flow characteristics of
the fan, pipe configuration, and the subslab. The fan and pipe
formulas are available but the subslab characteristics must be
measured.
11.1 SUCTION HOLE PRESSURE
Flow/Pressure Measurements By INFILTEC Blower Floor:
PRESSURE FLOW PRESSURE COMPUTED FLOW
("WO ("WC) (CFM)
0.136 0.150 83.27
0.120 0.134 78.70
0.100 0.110 71.31
0.090 0.095 66.27
0.080 0.082 61.57
0.060 0.058 51.78
These data then can be fit to a power law flow equation with the
following results:
* Correlation Coefficient = 0.998
* Flow Exponent (N) = 0.581
* .Flow at 1 " WC = 268.6 CFM
* Effective Leakage Area (ELA) = 12 square inches
Note that this basement is 25' by 40' with a perimeter of 130'. If we
assume that all of the leakage is due to the perimeter crack, then
this crack has a predicted width of about 0.008".
Now that we have a formula relating subslab pressure and flow, we can
write an equation equating the pressure generated by the fan to the
pressure loss in the pipe and in the subslab:
Fan Pressure = Pipe Pressure Loss + Suction Hole Pressure Loss
This equation can be solved for flow, and this flow can be used to
evaluate each pressure component. Suppose we assume the following fan
and pipe characteristics:
11.2 FAN PRESSURE
Kanalflakt T-2 fan specifications can be written as the
following equation:
Q = 270 - 116P
where Q is the flow through the fan in CFM
P is the pressure across the fan in " WC
75
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11.3 PIPE SYSTEM PRESSURE
Consider a system with ten feet of 4" diameter PVC with one 90 degree,
one vent cap, and one screen. An approximate equation for air flow
through a smooth round pipe of length L and diameter D can be derived
from handbook graphs:
Q = (.027LD EXP(2.75)) (P EXP(.55))
where Q is the flow through the'fan in CFM
D is the pipe diameter in inches
P is the pressure drop in one foot of pipe
L is the length of the pipe in feet
Assume an equivalent pipe length for resistance of pipe components:
one 90 degree Bend = 50 pipe diameters
one vent cap = 50 pipe diameters
one screen = 50 pipe diameters
Equivalent Total length = 150D/12 + 10 = 60 feet
Solving for pressure:
Fan Pressure = (270 - Qj/115
Pipe Pressure Loss = (Q/(.027LD EXP (2.75)) EXP (1.818)
Suction Hole Pressure = (Q/C) EXPd/N)
Substituting into the subslab system equation:
(270 - Q)/115 = (Q/(.027LD EXPC2.75)) EXP (1.818) + (Q/C) EXP(1/N)
This equation can be solved interatively for Q:
* Steady-state flow = 141 CFM
And the flow can be used to solve for the component pressures
* Fan Pressure = 1.11" WC
* Pipe Losses = 0.78" WC
* Suction Hole Pressure = 0.33" WC
This compares well with the measured 0.35 " WC subslab suction
generated by the installed system.
The pressure at the suction hole can now be used to estimate the
worst case pressure induced across the slab, far away from the suction
hole (called the "edge pressure"). In this particular basement, the
edge pressure was .020" WC when the pressure of 0.25 " WC was induced
on the suction hole by the blower floor. In some cases, the realation
between the suction hole pressure and the edge pressure is linear, but
in others it is not and in those cases the edge pressure must be
predicted by finding a curve fit between it and the suction hole
pressure.
76
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This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication.
FOLLOW-UP DIAGNOSTICS - HOW WELL DOES THE MITIGATION WORK
AND DOES IT MEET THE GUIDELINES?
Kenneth J. Gadsby
David T. Harrje, Lynn M. Hubbard and Craig Decker
Center for Energy and Environmental Studies
Princeton University, Princeton, NJ 08544
Many of the diagnostic procedures covered by the other presentations in
the Radon Diagnostics Workshop must be employed before a choice of mitigation
method is made. We will not review each of these procedures but rather will
touch briefly on items that have not been included in the other presentations.
Infrared scanning of interior surfaces
This diagnostic technique is used to uncover air leakage sites and air
flow patterns within the building. Outside air is normally a different
temperature, colder or hotter, than interior surfaces. When this outside air
enters the building it alters the local surface temperatures and thus can be
detected with an infrared scanning device which is sensitive to small changes
in surface temperature. Air flowing upward in the home from a cooler or
warmer basement environment again results in alteration of interior surface
temperatures. If the blower door is used to increase the upward air flow
(operating upstairs in the depressurization mode) the air path is made even
more evident. Since this is likely to be a pathway for radon transport,
the IR technique can prove useful in documenting such radon paths as well
as evaluating how well separated the living space is from the
basement/crawlspace. This degree of separation may directly affect the
choice of mitigation method.
Tracer gas measurements.
Flowpaths, as just described, can also be evaluated using a tracer gas.
The tracer gas is injected into the basement or other radon source locations,
and the path that air takes is then determined from local measurements, over
time, of the concentrations of the tracer gas. The tracer gas detection
equipment may take a variety of forms from simple freon leak detectors to
portable gas chromatograph electron capture-based devices. Cost may vary from
$100 to more than $5,000 per detector.
Another application of tracer gases is for evaluation of the air
infiltration/ventilation rate in the house or zone. One method is to add a
tracer gas, allow it to mix with the air in the space (natural convection
helps the mixing process, and running the furnace blower normally achieves
the mixing in less than 10 minutes), and then monitor the decay in the
tracer gas concentration levels. This "decay method" or "dilution method"
(see ASTM Standard E779 for details) allows one to directly determine the
air exchange rate, i.e., the faster the decay the higher the rate. Another
method, such as "constant injection" of the tracer gas, may employ tracer
emitters and passive samplers to evaluate the air infiltration rate.
Several different tracer gases can be used with this method so that flow
77
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from zone-to-zone can be measured. If each zone is maintained at a
constant tracer gas concentration, i.e., the "constant concentration
method", flow rates are then directly proportional to the tracer gas flow
rate to each zone. Systems are available to measure air infiltration rates
in 10 zones simultaneously. Rather than porbable diagnostics equipment,
this is computer-controlled ventilation monitoring equipment, priced in the
$20,000 range.
All of the methods described above evaluate building tightness and flow
paths and therefore may directly influence the choice of mitigation device.
During and after the mitigation device is in place.
The preceding discussion on diagnostic techniques is useful for choosing
the correct mitigation approach. Now we wish to shift attention to what
should take place during and after the mitigation device is in the house.
Mitigation installation diagnostics are important to see whether or not the
equipment is working correctly.
During installation of a mitigation system, such as subslab ventilation
where one is exhausting radon-laden air, adding a tracer gas to that air
allows one to evaluate where leaks in the system may be occuring, and whether
or not exhausted air is being carried back into the house. Of course the
radon itself serves as a tracer but the measurement equipment tends to be less
portable and more expensive than using freon and a freon leak detector, for
example.
Flow balance.
Many of the mitigation devices rely on withdrawing radon from critical
areas such as under the basement slab. Such air movement is governed by the
standard flow relationship, namely:
Q oc A y delta P
where Q is the air flow rate, A is the area for the flow passage and delta
P is the differential pressure. This means that if the air passage is non
restrictive, i.e., A is large, then a small differential pressure may be
all that the system can provide when the exhaust fan is flowing at its
rated Q value. On the other hand, if A is very small, delta P will become
very large and the rated Q may not be reached since the fan will stall, or
run very inefficiently.
Since there is often more than one branch to the mitigation system
piping, one wishes to make certain that all the critical radon source areas
are being appropriately treated. For example, in a house with a subslab
system treating a basement slab and crawlspace slab, one wishes to balance the
system so that both slabs are being treated equally. In the case of high
radon spurces in one area, that particular area should receive the higher
flow.
Diagnostic methods involve flow measurements in the various duct branches
using heated wire anemometers, pitot tube and micromanometer, or other flow
78
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measurement systems that can be easily inserted into the piping. Provision
for dampers in the piping lends itself to rapid flow adjustment of the
branches. Measurement of the exhaust for radon concentration level can
also help determine the best adjustment or balance of the system.
Energy and Radon Mitigation
Once the radon mitigation system is working satisfactorily from a
radon reduction point-of-view, it is then worthwhile to consider other
factors. Lowering the fan speed, providing the radon concentration in the
home does not rise, offers an ability to save energy in two ways: first
the fan electrical energy is reduced and second one limits the energy loss
assocaited with the conditoned interior air that is exhausted with the
radon laden air. From a diagnostics standpoint, energy savings from either
a lower fan speed or smaller fan can be determined by the use of a
wattmeter. The evaluation of how much additional air is being removed from
the house must rely upon air exchange measurements using tracer gases. For
example, placing a tracer gas in the basement and measuring the
concentration there and then measuring the concentration in the exhaust
from the subslab system allows an evaluation of how much of the air was
basement air and thus to evaluate the energy penalty. It is evident from
test home data that exhausting systems do alter the "normal" air
infiltration rates and raise energy use. This often can be limited to a
minor increase by appropriate mitigation system adjustments.
When mitigation systems are used which cause air to leave the
basement, we must be sure that the air flow is not causing a pressure
reduction that results in combustion products from the heating system to be
drawn into the basement and home. Use of heated wire anemometer, pressure
micromanometer, and smoke tracers can prove useful diagnostics tools for
evaluating proper flow direction in the furnace exhaust. Remember that the
greatest tendency for reverse flow will be under mild weather conditions.
Also, where the piping of the mitigation systems leaves the
conditioned space, the opening must be completely sealed to avoid
undesirable energy losses. Use of smoke sticks, tracer gas or IR scan will
immediately revel such shortcomings. In the same area of "good
installation" the system piping must have the appropriate slope so that
condensing moisture will not form a local puddle and plug the exhaust flow.
This is a very real problem with large volumes of water being condensed.
Use of bubble levels and careful measurements and firm bracketing avoids
these difficulties.
Conclusions
This has been a very brief review of some additional diagnostic
procedures that should prove useful in the choice of the mitigation approach
and whether the mitigation system is performing as desired. Diagnostic
techniques are focused on providing quantitative and qualitative data to
improve the chances for successful radon mitigation. At times the most
critical procedure will prove to be something very house specific, meaning the
investigator must continually ask critical questions and ponder those
measurements that "don't make sense" while looking for the "right
solutions."
79
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PART C WORKSHOP DISCUSSIONS
The following are the actual discussions that took place in the
Workshop as transcribed from audio tapes. Efforts have been made to
identify the originators of question (Q), answers (A), or comments (C).
This identification is by initials in the parenthesis before each quotation.
Please refer to the list of attendees for this information.
As has been the rationale throughout this Workshop the discussions
will be treated in four phases:
I. Radon Problem Assessment
II. Pre-Mitigation Diagnostics
III. Mitigation Installation Diagnostics
IV. Post-Mitigation Diagnostics
80
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Radon Diagnostics Workshop, 1987. Phase 1 Discussion.
Phase I - WORKSHOP DISCUSSIONS - RADON PROBLEM ASSESSMENT
M. Mardis, Chairman
C(M.M.) "Phase I is the Initial Radon Problem Assessment and we want to
focus our attention on diagnostic tools that will prove useful to identify
radon source strength and location; to characterize the existing building
structure; evaluate occupancy factors; and measure the radon concentration
in the different zones within the structure.
The panel will begin the discussion, and we will start with mobile
scans with Mike Koontz:
C(M.K.) "I would like to start out with a few background comments about a
statewide survey in Florida. That is, I'll start with a regional
perspective and lead into the specifics of a house."
"The purpose of the Florida study is to identify areas of the state
which are problematic in terms of radon. There is an environmental rule
there that basically states that if an area is declared to have problems
then certain types of radon-resistant construction methods are to be used in
new construction. In that study we're measuring radon indoors, short-term
with charcoal canisters, and measuring soil gas concentration. We're also
using portable scintillometers to measure radiation instantaneously inside
and outside the houses."
We're guiding our survey as to high-concentration areas with USGS 1-
24,000 scale maps representing 8 mile x 8 mile squares (quad) of land. We
originally thought that as we had our field techs going from one place to
another searching for houses and making these measurements it might be
useful to use these portable scintillometer to make measurements while
driving to give us a better feel for local variations. Unfortunately we
found that the road surface was a confounding factor, and we couldn't make
reliable measurements that way. This leads to my question with respect to
measurements from mobile vans: what sort of false positives might you see
due to road surface or other potential confounding factors?
"Alan spoke about mapping data from NURE or other sources. We've found
that the 1:24,000 quad is a convenient mapping tool. We've looked at the
NURE data, not only the radiation values, but another possibly valuable
addition from the NURE data is that they do have so-called geologic map
units associated with each reading. Again, bearing in mind that at least in
Florida, flight lines are sometimes 18-20, miles apart, depending on
whether you're looking N-S or E-W. Nonetheless, the 1:24,000 quad can be a
convenient way of looking for subcountry variations at a gross level. The
NURE data, both the brightness and the geological data, seem to be helpful,
and we're seeing also that there are fairly good correlations between soil
gas' concentrations and indoor concentration, again, at this more aggregate
level. I don't think it works at the neighborhood level, looking at house
to house variations.
"These state-wide data can be used to identify potentially "hot" areas.
Within a given area there may be variation of an order of magnitude."
Q(T.T.) "During your work in Florida, you did gamma surveys. We've heard
81
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Radon Diagnostics Workshop, 1987. Phase 1 Discussion.
here that some studies have shown that gamma and other emanation studies in
some parts of the country (like Grand Junction, Colorado) are usefully
correlated with Indoor levels, but that in other areas (such as in the
Reading Prong) the case is not so straightforward. What experience did you
have in Florida?"
A(M.K.) "We haven't analyzed all the data yet, but we did see that the
strongest correlation of indoor radon concentrations is our soil
measurements made with alpha tracks. We do see some correlations, even
indoors, between concentrations of uranium and radon, but we're not in a
position yet to say how well It works."
Q( ) "How are the soil measurements made?"
A( ) "Without the traps they're in 12 to 15 inches."
Q( ) "What kind of correlations are you getting?"
A(M.K.) "The correlation coefficent between soil measurements and
Individual houses has been 0.5, whereas using the quad as a unit of analysis
with the soil measurements, the correlation coefficent has been 0.7. We've
taken measurements in, say, 4-6 houses per quad. 0.7 is the correlation
between mean soil concentration and mean indoor concentration. Q(M.M. )
"Do these houses have basements?"
A(M.K.) "This becomes an issue when one is doing mass screening using
charcoal canisters indoors and looking for problem areas. Ideally one would
be able to identify a "marker house" of a design found throughout the state
so as to avoid the confounding effects of measuring in houses of completely
different construction types. Fortunately, in Florida, perhaps 75% single-
family homes are slab-on-grade, so we've restricted ourselves to that type
of structure."
Q(D.S.) "I'd like to focus in on that correlation. The correlation is
acceptable, but is it really the soil gas and source strength? Or, is it
that plus the transport in the sort of homogeneous conditions found in all
your houses? We are getting closer to the "radon availability index". The
reason that you got a good correlation may be not only that the soil gas
level is related, but that it is available because of the transport
ability."
A(M.K.) "I agree, and we might want to follow the dual method Alan Tanner
suggested which measures soil permeability as well as sour strength,"
Q( ) "How many alpha track soil measurements did you make?"
A(M.K.) "We did one per house for about 3000 houses."
Q(T.T.) "Where did you put it in relation to the house?"
A(M.K.) "It's fairly close to the slab, perhaps three inches away 12-15
inches deep. We also take scintillometer measurements at that same
location, and at a location on the opposite side of the house. We've seen
substantial variation between the two sides of the house in those
instantaneous radiation measurements."
C(W.L.) "Someone commented this morning that you have to go down at least a
meter."
C(A.T.) "I did some work in Hillsborough and Polk Counties in Florida,
where the [radon] problem is the worst, and Florida is really quite unusual.
Often one will find 10 or 20 feet of well-sorted (in other words, the grain
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size is fairly uniform) pure quartz sand, in other words, a very uniform,
homogeneous soil. The soil is of pretty high permeability -- it's pretty
fine stuff, but it's well sorted. The diffusion coefficient is probably
very characterizable and the permeability is reasonably so. The water table
can come right up to the surface, or it can be down a ways, so there will be
seasonal changes in dryness and wetness. But in comparison with most areas
of the country, the soil is the ideal, almost the physicists' mode of
homogeneity. Under those circumstances, placing track detectors at that
shallow depth is probably not unreasonable. At some point I'd like to get
into a discussion of the use and abuse of track detectors."
C(D.S.) "It is important to say why measurements agree or disagree as we
discuss these points."
C(R.S.) "So, Alan, you're saying that it's not surprising that one sees
some degree of correlation, at least at a gross spacial scale just because
it is so uniform. David made the point earlier that if it's pressure-driven
flows into the house (and of course you're not really seeing that with alpha
track detectors buried in the soil --at best you're seeing diffusive
radon."
C(A.T.) "This may be the time to talk about alpha track detectors."
Q(T.T.) "Is it true that the bulk of your studies in Florida is on tailings
and reclaimed pits?"
A(M.K.) "We're actually doing uniform coverage of the state."
Q(T.T.) "I was down there in the early seventies to study housing built on
a reclaimed pit. I was surprised to find that my hotel room in Lakeview was
hotter than the housing I was studying.
Q(D.S.) "Are there other experiences with the use of alpha track soil
measurements?"
A(I.N.) "When Teradex first came out of these kits, we sent them to 60
homeowners in central New York, and put four monitors around each house. It
was very simple and inexpensive. Simultaneously we put three alpha tracks
in the house itself as well as in the water, in their toilet. We found
absolutely no correlation of any of the radon measurements in the soil nor
the indoor measurements.
Q(D.S.) "Can you give us some specifics as to the placement in the soil?"
A(I.N.) "It's the same technique: 12-18 inches into the soil, about three
feet from the foundation, as specified. This may not have been a good
idea."
Q(D.S.) "Tom Peake, could you speak on this issue?"
C(T.P.) "The office of Radiation Programs of the EPA has a program called
the House Evaluation Program. We are taking some work that ORD is doing
with the research in mitigation, and applying it to the private sector.
These houses provide us access to homes which have been fairly well
diagnosed. We're taking some soil gas measurements around the houses, 4 to
5 feet from the foundations. We are using grab samples, similar to what
Alan has been doing; he's working on a soil gas protocol for us. We're
taking the information which he's giving us with help from Jay Davis. We
took measurements near houses and away from houses, three ft. and 15 feet.
We found generally an increase in soil gas concentrations away from the
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house. We did not get a good correlation between radon soil gas values and
indoor Rn levels though correlations were positive. We had one house with
550 pCi/L in the basement, and an average of measurement of 800-900 in the
soil, 15 feet away from the house. Maximum levels were higher than that."
Q(D.S.) "Do you have alpha track measurements as well?"
A(T.P.) "We have some alpha track measurements, but results are not back
yet. We had some problems with moisture condensation on the alpha tracks.
And I know Charlie Kuntz from New York had trouble with the water table
going up into the alpha tracks. We also had trouble with atmospheric
dilution because of the way the dirt is settling."
C(M.M.) "Tom brought up that in making alpha track or charcoal
measurements, in fact any type of soil-gas measurement, one has to take into
account the influence of the house. He noticed that soil gas radon levels
increase with distance from the house, and that there is a lot of
variability."
C(R.S.) "Looking at Figure 9 of a house, we see where grab samples were
taken from a soil probe, usually a meter of 1.5 meters deep. We see levels
of 300-500 pCi/L at one point. Around the house the house the numbers vary
to 89,000 pCi/L. Back fill questions, location of concrete slabs, and other
factors account for three orders of magnitude variation."
Q( ) "Has anyone taken soil moisture content measurements at the same time
that they took soil radon gas measurements?
A(A.T.) "I can show some related material."
Q(M.M.) "Let me use that question to take a step into another area, still
dealing with soil gas measurements, but in the area of mapping of radon soil
gas. The question is mapping radon soil gas permeability and moisture and
how these relate to one another."
Q(R.S.) "Another question: You've been taking measurements, both alpha
track and grab samples, and you've discussed confounding variables, such as
moisture. Could someone comment on what other confounding variables might
affect the placement or depth at which you grab a sample?"
A(R.S.) "If you get down below a meter or a meter and a half, you lose that
confounding variable, except in really permeable soil."
Q(D.S.) "But Rich, could you comment on other confounding factors. We're
talking about diagnostics, about how you can get really meaningful
measurements. One factor is depth of placement and another is water and the
water table and how they affect the measuring device. Are there others we
should point out now?"
C(A.T.) "Not just the depth of the water table, but the percentage
fractional saturation of the pores is an extremely important factor in both
diffusion coefficient and permeability."
Q(D.S.) "Is there an estimate as to how these connections are made?"
A(R.S.) "It's important to note that moisture does two things: it
increases the emanating fraction (or emanation ratio, if you want to put it
that way). But at large enough moisture saturations in the soil, it
decreases convective flow through the pores because as you begin to fill up
the large pores, you lose your convective flow pathway."
C(A.T.) "These data are actually Roger's... the moral of all this is the
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following: In theory in dry, porous media, the diffusion coefficient is
independent of pore size and the grain size, as long as you're within the
mean free path of radon, which is quite small. But in the real world, the
diffusion coefficient drops rather dramatically as you, (looking at chart:
these are all orders of magnitude now and this is the diffusion coefficient
in free air)... as fractional moisture saturation increases, you get a
change in the diffusion coefficient of four or more orders of magnitude.
Even in principle, you get the same drastic change in permeability as you
increase the moisture concentration, and both of these are strongly affected
by... if you were to think of the water in the pore space as merely
occupying the space the air would otherwise be in you'd have a curve that
went something like that... and only when you get down to nearly complete
saturation would you have a marked change in diffusion coefficient. The
answer is that the water, via surface tension primarily, tends to block
inter-pore communication, and therefore the water has a disproportionate
effect.
"Now I can get back to the question of alpha track measurements. I
have to say that my views are not necessarily those of the Teradex
Corporation. This is an experiment conducted by Willashevitz and Pyrictonov
in 1959: they had a sealed tube, with ports for examining the concentration
of radon in an open space, but in this otherwise closed tube, at various
distances along the length of the tube. It was radium-loaded sand, and a
measured diffusion rate d/porosity measurement of .0134 cm2/second, and
these data were taken at steady state. Now think of this as a track
detector cup over a column of earth. What it shows is that the track
detector cup to some degree is actually performing an exhalation measurement
on that porous medium. This .0134 cm2/sec is a fairly good diffusion
coefficient, not quite as high as that of nice dry sand, but it's a good
deal more than that of a lot of sandy clay loam; for instance, in which the
curve would look much more like this... The implication here is that as the
moisture concentration varies, the concentration of radon reflected in the
track detector measurement is going to vary considerably, even though the
actual radon production and the radon value in the pore space is remaining
constant, or even increasing slightly. So, you do not get a real
concentration measurement using a track detector in the ground, or in a
porous medium. Now there-is a modification here, because while this is a
strictly one-dimensional situation, in real life there would be
contributions from the side. So, the situation would not be as drastic as
implied by the experiment. But you do have to remember that you are looking
at a cross between a concentration measurement and an exhalation measurement
that is going to be very drastically affected by moisture in the ground, and
which is going to show seasonal variation and variations due to sudden
precipitation and so forth. The closer you are to the surface, the worse
the situation is going to be."
Q(M.M.) "Let me ask you a question about the moisture effect on the alpha
track. Your chart shows some concentrations differences based on moisture.
What scale are those? Are we talking about differences of 10% as moisture
changes, or are we talking about 50%?"
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A(A.T.) "I would think that changes of 50% would be more typical."
Q(M.M.) "Would you say then that based on that and on typical moisture
ranges that the alpha tracks would not be a useful tool?"
A(A.T.) "There are two considerations. One is how you use it, and another
is how you interpret the information you obtain from it.
"There is even another caveat, though, an important one: this study
was done for completely different reasons by ChrisJensen and Mumquist, and
what they had here were results from two holes side-by-side, and the one on
the left-hand they made track measurements where the cups were used at
successively greater depths, and back-filled so that there was no
competition from the atmosphere, i.e., no atmospheric dilution. In the
depth range down to six meters they have (although there is a lot of scatter
in the data) a monotonically increasing radon concentration with depth.
"In the left-hand experiment they had the track detector mounted in a
thimble that could pull up out of the ground after the experiment. That's
rather'difficult to do and Charlie Kuntz, in his presentation, had a control
over the atmospheric dilution.
"In the right-hand experiment they merely drilled the hole to a given
depth, put the track detector in the bottom and did not back-fill it behind.
What you see is that as you go down in the ground, the permeability
decreases, both because of moisture increase, and because of increased
packing of the ground with depth, and the atmospheric dilution takes over,
so that you get very low results. This is strictly an artifice, and means
nothing. If you put track detectors in the ground, you've got to back-fill
them. I was thinking about what happens when the track detectors are
sampling a variable information volume. It may be that that's a saving
grace and in fact a pretty good way. It's been noted for a long time that
track detectors are an integrating device, and integration is general for
soil measurements is very desirable. There are some data indicating that
there is a seasonal effect of a factor of five. But, if in fact, the
measurements from the track detectors are a function of variation in
permeability and in the diffusion coefficient, maybe that's a good thing,
maybe you do iron those things out, and get a better measurement. The one
thing I would advocate is that people reduce the size of that open space.
This may cause trouble with moisture on the surface of the track detector,
but I think that it's worthwhile to consider experimenting with something
smaller than the typical track detector cup.
C( ) "There have been some studies done comparing grab samples, alpha
tracks, etc. I have here a Swedish paper which describe traverse with
charcoal, alpha tracks and then the grab sample. From the information it
looks like the different instruments measure the peaks at the same place.
However, the magnitudes of the peaks are different in every case. So, I'd
like to caution everyone that even though it looks as though these different
devices might have some potential for measuring radon soil gas, only the
grab sample can be used to get a permeability measurement which is
important. Also, we should remember that when someone says they've measured
soil gas measurement of 1000 pCi/L with an alpha track detector, that may
not mean the same thing as the same measurement made with a grab sample.
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Many people have been using a classification method developed by the Swedes,
under which an area with 1350 pCi/L would be considered a high-risk area.
We don't think that we can use that method as is. In the near future we
hope to compare some of these different types of measurements around houses
among themselves. We've already had a contractor do a little work, and his
results are similar to the Swedes: that different types of instruments can
be used, but that one must be careful about the configuration of the
instruments and their use in different situations. We need to improve the
protocols for the use of these instruments, because at the present time
everyone is using them in different ways. We need to know how these
different measurements relate to one another."
Q(M.M.) "That's a good point... we've talked about the direct, Lucas-cell
type measurement, and about alpha track measurement. There's a third,
fairly common type, which is the charcoal canister. After we discuss that a
moment, I'd like to see if we can agree on a standard soil gas and soil
permeability technique, based on the experience we have among us in this
room. Which is the most simple, best technique?
Would someone like to comment on the use of charcoal devices for soil gas
measurements?"
A( ) "Why don't you talk about Vern Rodgers' experiments?"
A( ) "In essence, Vern Rodgers compared charcoal canisters to track etch
and grab samples and found that data from the charcoal canister (the same
ones we use indoors) did not properly represent the levels of radon actually
found in the soil because the charcoal canisters acted as a sink for radon.
You weren't measuring the actual behavior of the soil. The Swedes, in the
paper cited earlier, found that charcoal canisters gave the lowest soil gas
concentrations of any of the methods. Moisture can also be a problem with
charcoal canisters."
Q(M.M.) "Were these side-by-side measurements for which the charcoal
canisters gave lower values than the alpha tracks?
A( ) "There's also variability in all the measurements."
Q( ) "How much lower are the readings from the charcoal canisters?"
A( ) "20-50% less would seem typical. It's not that charcoal canisters
can't be used -- it's the way they are configured now."
Q(M.M.) "What is standard canister out there now?"
C(R.S.) "If you dig a hole you can put a pipe in the ground more easily.
If you have a major soil gas radon concentration why not use a grab sampler
or something? You can do it, because you can put a pipe in the ground just
as easily as you can dig a hole."
C(A.T.) "The contention there is that you have temporal variability. How
do you get around that?"
Q(T.B.) "We've talked about grab samples and alpha-track detectors. What
happens with soil gas concentration as time goes on and how do we get a
handle on that?"
A(W.B.) "It appears that seasonal variations are stronger than day-to-day
variations, at least as compared to indoor radon levels. That seasonal
variation is going to have a lot to do with where you are measuring. If,
for example, one measures where the soil is frozen for six months of the
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year, soil gas values will be higher. But in the summer, soil gas values
will be lower. It basically follows the same path as indoor radon levels.
For instance, you would get very different soil gas values in Florida, where
the soil does not freeze, than you would in New York or Pennsylvania. We
have to watch out for freeze and thaw conditions because of elevated soil
gas levels.
C(D.S.) "I'd like to interrupt. We're trying to address the accuracy and
precision of different approaches, including alpha track, grab samples and
carbon canisters. I'd like to outline how good those measurements are.
We've tried to address some of the confounding variables. There may be more
variables confounding carbon measurements than the other methods. We also
heard about the short-term vs. long-term integrating effects of these
methods. Let's try to keep the discussion focussed on specific points
before we move on."
C(M.M.) " To finalize our discussion of soil gas measurements, I've heard
several discussions about differences between the three techniques. About
five months ago in Washington there was a meeting of people heavily involved
in making soil gas measurements. We agreed that the simplest and most
straightforward method is the direct measurement. I think Alan was touching
on that when he suggested that a pipe be driven into the ground. The direct
method is the most representative and gives a real value. One disadvantage
is that it doesn't give you information on time variability. Another point
is that once you have a measurement of Radon in the soil, there still
remains the question of how easily the radon can move or migrate to a
structure. In short, we mean permeability. Can someone factor those two
together for us?"
A(A.T.) "Well, they are the factors. Permeability is not the only one of
course; diffusion is a valid method of motion, and I think that because of
the aggregate below the slab, diffusion may in fact contribute more than we
think to the reservoir which that aggregate layer makes up. The process is
then diffusion into the reservoir and then when you get an underpressure in
the house, you pull that quickly in by flow."
"You can characterize the undisturbed ground with respect to radon
availability being a product of radon concentration times the mean migration
distance, by whatever transport mechanism. Does that tell the whole story
or do you have a two-part problem, one of getting the radon to the subslab
reservoir, and the second of getting it into the house? By assessing the
first, do you get a handle on the whole picture, or not? In time the
Berkeley people will give us the coupling coefficients."
C(M.M.) "I think the variability we're seeing between soil gas levels and
indoor levels definitely says that the second process may be a major
factor."
C(R.S.) "As Brad pointed out in his discussion this morning, it is a
coupled problem. You've got the impedance across the building shell, and
the impedance of the soil. That means that just knowing where the radon is
high in the soil is not enough; we have to know at which points the radon
can gain entry into the building."
Q(K.G.) "What about some of the soils we tend to find in this area which
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tend to be heavy clay and wet? You can pull a vacuum with a hand pump when
trying to take a gas sample... as a matter of fact, if you take repeated
samples, you can see the radon concentration go down as you deplete the
source. How do you measure the soil gas concentration there?"
A(A.T.) "If that, in fact, is the location of the radon source, then you
don't have a problem."
C(K.G.) "What do you mean we don't have a problem elevated radon levels
are present?"
C(R.S.) "Alan's point earlier was that if you have a diffusively driven
reservoir, the house pumps on it in a diurnal cycle reflecting the fact that
the indoor-outdoor pressure difference flows a diurnal cycle. We see that
the reservoir may be depleted in one part of a day and replenish itself in
another. This may explain what's going on near houses where the soil is of
low permeability but where there is a reservoir under the soil."
Q(A.C.) "Do you see a diurnal change in the level of the reservoir?"
A(B.T.) "We haven't see it yet."
C( ) "But in one slide you showed in Philadelphia did show a time-varying
soil level."
C(R.S) "But the frequencies didn't match."
C(A.C.) "Well, then your facts don't match your hypothesis. I'm not saying
that was the situation at that particular house but rather that it is a
plausible explanation for some house situations."
C(T.B.) "The problem is that you've sampled using a small hole about a
meter deep. I might come in and excavate all that impermeable red clay off
the top, and discover that four feet down is a layer of shattered shale
which you've missed. We don't have x-ray eyes; soils aren't uniform and
isotropic. All our models are uniform and isotropic, but if you were to
make a finite difference model, I could imagine many soil configurations
that could give you some very anomalous results. I see that occurring time
after time."
Q(AC) "Have you considered going through the slab and measuring soil
permeability below the slab?
A(K.G.) "Yes, on that house we did just that, and there was no permeability
under the slab."
C(T.T.) "The way I've accomplished that over the years is simple, but
requires a back-hoe. I just dig an eight foot trench, get down in the
bottom of it, and I take a flux measurement through the bottom of the
trench. The soil gas doesn't tell me anything. I've mapped it, I've tried
to correlate it with indoor concentrations. I've used pipes to measure it
at various depths in the same hole. I really question whether these soil
measurements are getting us anywhere."
Q(M.M.) "Let me see whether I can put this in a final question then. Do we
fee-l that soil gas measurements are a useful, viable and cost-efficient tool
for diagnosing radon at a site?"
Q(A.S.) "What is the question which soil measurements are answering?"
A(W.L.) "Radon availability."
C(A.S.) "That's more than soil gas then?
A(A.T.) "Yes. I think a soil gas measurement per se can tell you something
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only if it's very low or very high. But without the permeability data the
procedure is highly questionable."
Q(W.L.) "This is where the question of nomenclature comes in. In
Montgomery we agreed that the product of two factors defined the entry rate.
They are radon availability and transport efficiency. Transport efficiency
itself is a function of soil permeability, pressure differentials, and so
on."
Q(T.B.) "But how could we discover irregularities in the composition of the
soil, for example, pockets of sand, using soil measurements?
C(another person) "Don't forget that the ratio of surface area to volume
for clay is very large, so it gives very high emanation efficiency for the
radon. The transport efficiency is clearly very poor, but put the clay next
to a layer of sand, and you can get the transport."
C(W.L.) "The soil gas measurement is very close in my mind to the radon
availability. But without these other factors the situation is still very
hazy."
C(A.T.) "Wait a minute -- I don't believe we've agreed that radon
availability is the value of the radon concentration in the soil -gas. When
I say "radon availability" I'm very definitely including the soil
permeability, the diffusive and advective flow, in addition to the radon
concentration in the pore space."
Q(R.S.) "How then do you factor in the radon migration? How would you
handle your definitions for a house which is pumping radon from the soil?"
A(A.T.) "I define it as radon concentration in the pore gas times the mean
migration distance, which incorporates both the diffusive and the advective
flow. The computation of that may be subject to change. The concentration
of Radon alone is not a sufficient criteria."
C(E.K.) "I'd like to go back to the charcoal. When we developed the
charcoal method in New York, we meant it to be used indoors, at comfortable
temperatures. Using it outdoors raises a series of new questions."
C(M.M.) "I'd like to sum up by noting that we're not certain how useful
soil measurements are at predicting radon problems at a given site. I
think, though, we are in general agreement that the most effective
measurement of soil gas is the direct measurement, and that we need to know
the permeability of the soil. "
Q( ) "What is the progress that we are making on soil gas sampling?"
A(A.T.) "I think I can answer that question and the one that Mike Koontz
raised when he asked whether soil gas sampling was a viable technique
evaluating radon problems on for a single lot. I think a good deal of
progress has been made. A lot of measurements have been made, and I don't
think there had been a lot of measurements before last summer...well,
certainly there have been some, but there have been a lot more since. New
York State ERDA(?) has done a lot of them, Jay Davis has done a lot, LBL did
a lot last summer. I do not think it's going to be viable on a single lot
basis, because in any given area you have to develope confidence that
you're getting statistical validity in your measrements. You can't afford
to make too many measurements on a single lot before it gets less expensive
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to build the house the right way in the first place. But if you're talking
about a development that mayt encompass a couple hundred houses and some
acres of land, and you can afford to grid and spend several days doing it,
there may (or may not) be a viable technique there. I don't think we have
enough information at the present time to prove that. It will take a full
year or so of gathering data to indicate the variability of a set protocol,
whosever it might turn out to be. We have some indication that the results
are going to be highly variable on a single lot. If we saw the same
variation that Brad a Terry were talking about as a general rule, I don't
think it would be a viable technique."
Q(H.T.) "What is the mean migration distance you've been talking about?
A(A.T.) "It's the distance which radon moves, by any transport process or
combination of them, in it's mean life, which is 5.52 days. If you will
look in either Clement's thesis, or in Sherry et al. in 1984, 'Factors
affecting Radon Transport in Sandy Clay Loam' in Journal of Geophysical
Research (the published 1974(?) JJR(?) article doesn't contain the
equation), you'll see that the J, the exhalation Current Density under
steady-state conditions is equal to gamma times the square root of the
diffusion coefficient times the porosity times the decay constant. Gamma is
equal to beta plus beta squared plus one. Beta is V over 2 times the square
root of D epsilon Lambda. It's a mess! Multiply that by 5.52 days and
you've got it."
Q(D.H.) "I'd like to step back again. The first talk with Mike was a very
general survey over a land area, looking to see whether it showed signs of
having problems. Then we went into very a very detailed analysis of the
many different ways we could sample radon in the ground, and then we came
back to the conclusion that a direct measurement (for instance, a grab
sample out of a hole) was the best way of getting local information. Now I
think that you've just stated that you would be afraid to use that technique
for a given building-size plot, but that for a larger plot you could. Are
we back to the simple surveys where we started out? We started in the big
picture, and then we took this very detailed method and showed all of the
things which Terry was pointing out, with different types of sand and
everything else. But we ran into trouble in the small picture, and we're
back using this very detailed measurement, but on a larger scale. Aren't we
competing now with much simpler methods?"
A(A.T.) "Well, No. When you're talking about the gamma survey or the use
of the NURE data or regional type information, when you're talking about
square miles and larger areas, all you're going to do is to predict that
most of the houses are going to be fairly low or else threatened enough that
one should use radon-resistant construction methods. You can't make
predictions about what the radon will be in any individual house. When you
start talking about sampling on a given lot, then you're trying to be
specific about whether or not you're going to have a radon problem at a
house on the site. You can't evaluate that possibility at all by taking a
simple measurement of radon in the upper foot of the soil."
C(D.H.) "You sound leary of making measurements down at that small scale."
A(A.T.) "I'm not so leary of it, I just think that you may have to make so
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many measurements that the costs of testing can increase above $2000, which
is already more expensive than most estimates I've heard for making a house
radon-resistant."
C(M.M.) "The National Association of Home Builders says that builders can
build radon prevention into a house for $300 to $400."
Q(M.M.) "We can return to this topic later, but for now we'll have to move
on. We've talked about identifying soil gasses and measuring levels in the
soil; now let's discuss how we can identify a problem house? Not a survey
of a given area or a specific, measurement for a lot, but rather, how can we
identify already constructed houses that -may have; problems? I'd like to
narrow this to screening techniques for now, and we ca-n move to techniques
for measuring radon in specific zones of houses a little later. Does any
one have any comments on surveys to aid in identifying of hot spots?"
Q(R.S.) " Mike, doesn't it depend a lot on what level ytK3/re operating? I
think that as Alan Tanner indicated earlier, if you have information such as
NURE or other radiometric surveys, soil permeability information and other
things, you might be able to locate areas where you would do more detailed
surveys. I think it's fair to say that we're not there yet in terms of
compiling all that information and putting it together in a way that you
could, with some assurance, say that a given area has a problem and that one
does not."
C( ) "But we've done it."
C(A.C.) "Yes, I also disagree with you, absolutely. I've taken the twenty-
eight hundred readings in Maryland [that University of Pittsburgh has from
Maryland], and I can tell you exactly which counties or parts of counties
have a problem, and which ones .do not."
C(R.S.) "But that's an ex post facto.
C(A.C.) "That's right. Now as far as I'm concerned, tbe people who are
using the NURE data and who think that it's a great technique, when they are
confronted with hot spots that we've found using other techniques, they have
confirmed that they should have seen them, but they didn't."
C( ) "That's not entirely true."
C(A.C.) "They all come back and say, Hey! Clinton shows on the NURE map,
but nobody mentioned it."
C( ) "But nobody looked for it before. The reason why the geologists
haven't been able to find the hot areas is that they haven't looked for
them."
C(A.C.) "I'll tell you the £aae thing which I told a. geologist last week.
There are twenty to twenty-five spots in the Reading Prong area of New
Jersey, where the geologists who identified the Clinton Knowles area in 1971
as a good place to mine uranium. In that part of New Jersy there are twenty
to twenty-five hot spots that he was on personally in 1971 which were as
high in uranium content as Clinton Knolles, and every one of those should be
as much a hot spot as Clinton Knolles, but no one has found them yet."
C(R.S.) "I didn't actually mean to get us started on this. I thought what
that meant was the sort of survey information which the states generally
have, and it's a one- or two-page document describing the kinds of houses,
where they're located, and that in fact may relate to geological maps and
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other information. But housing characteristics, occupancy characteristics
gives you some idea of the level of concern we should have about the houses
in this area. Is that a valid set of survey information? It's readily
available for most states, and part of existing programs. How much of that
do we as people interested in finding problem houses and fixing them should
we try to solicit? Another source of readily available information is
University of Pittsburgh Data."
A(R.S.) "What I was starting to answer earlier was the question of what
sort of screening surveys we should do first. Is that what you were
asking?"
Q(M.M.) "Let me rephrase the question. I was specifically talking about
the screening survey. Given the fact that we have some information, whether
geological or NURE or whatever, that would focus us on some area in a given
state, what is the next step in identifying radon problems in given houses
or groups of houses in this area? I'm talking about specific surveys,
making indoor measurements. These are the data that Chuck would later used,
and it's been generated in a random way, Bernie Cohen's data."
C(R.S.) "One of the things which you've started to do, a step in the right
direction, is to wintertime charcoal screening surveys. They don't tell you
anything about the annual exposure, but it could tell you something about
hot spots which you can then correlate with external information."
A(A.C.) "In looking at .16 states, at least 12 out of 16 states had at least
one county with at least 50% -of the houses above 4 pCi/L. If I lived in a
county in which 50% of the houses measured above 4 pCi/L, I would certainly
have my house tested, and every house in that county should be tested, there
is no other way to tell the extent of the problem."
C(R.S.) "That's right, I think you could use that as a gross screening
survey, that someone would have to follow up."
A(A.C.) "The ten-state survey being done right now by ORP for the 2000
cannisters being run followed by 1000 follow-ups is going to really tell you
whether those ten states have a problem and in which parts."
C(R.S.) "But it's very important to do it in the wintertime."
C(T.P.) "I'd like to say something about the surveys which ORP is working
on. We're just now getting some of the results back from the state surveys,
and we have only preliminary results. I'm not exactly sure how accurate
they are. Using geological characterization, at least for Tennesee, we've
been able to find geometric means higher in the areas predicted to be high.
C(M.M.) "So the state survey data may correlate with the areas predicted to
be high. To be sure that this type of data is comparable, we need to
standardize, to focus on standard measurements made in these houses. I'm
not sure whether it has to be in the winter. It's true that doing it in the
winter will give better closed-house conditions, but if you can achieve
closed-house conditions, and if you can measure on lowest global levels,
then you tend to maximize the values you find for a screening purpose, and
your data will be pretty good."
C(G.F.) "Just a remark back to Chick's comment, I think New Jersey's
approach in their follow-up, looking for another cluster situation like in
Clinton, is mainly their fan-out program, when they have a discovery home or
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an index house of 200 pCi/L. It's an excellant approach to find those
pockets around the state that indeed have elevated homes in the vicinity. I
don't know if Pennsylvania is doing that or other states you are in touch
with, but even though it costs a lot of money, it's to find the pattern of
high-level homes in a given territory."
C(A.C.) "Of the counties where I'm saying that 50% of the houses are above
4 pCi/L, most of them do not have any house with levels above 100 pCi/1.
But the number of houses in the range 20-50 pCi/1 are far higher than
average."
C(T.P.) "When you do look at that data, you can bring that back to the
geology of the area. I'm not saying that this could apply to a specific
house, but suppose you look at a number of homes on black shale which is
elevated, or suppose you look at a large number of homes which are elevated,
and you examine the geology and the other information, you can use that to
go and find other high levels."
C(G.F.) "We're sitting right here on a Triasic Ridge, and there was no
comment made by state geologists a year and a half ago that this was at all
a probable area for radon. So, I disagree with you on that."
C(T.P.) "The EPA has a national radon map. I've been looking at the data
that goes with these maps, and the triasic basins are responsible for
elevated levels, black shales are responsible for elevated levels, so I
think we have to look into some of the other areas. "
C(M.M.) "If we could stay off geology for a few minutes here. Gene was
talking about fanning out around high areas once you've discovered them, and
making additional measurements. That seems to be a good policy. Chick was
talking about taking measurements in every house in the United States. That
would tell us all we need to know." (laughter)
C(A.C.) "You've misquoted me."
C(R.So.) "We need to get the permeability better documented. This variable
is jumping out at everybody, but there's almost no discussion of the
methodology and protocols needed to pin down this variable. We should
always have two parameters for each house. We keep describing a situation
in which only one of two parameters is known, the other one is guessed, and
the explanatory power is very low. People have been aimed too much at
measuring radon concentrations."
A(A.T.) "It isn't that we don't understand it, we just haven't measured it.
First of all, there is a data base, though it isn't all that we would like.
Most counties in the U.S. have data concerning perk tests and soils
information, or the Soil Conservation Service has information. The Berkeley
group spent a long time studying soil groups and which ones had tendencies
to be permeable. There exist very specific data, sometimes with very high
density, on things like perk tests. They may not be quite what you want,
but.they do give you a strong clue. In the state survey effort that Tom has
been talking about, those data are used as clues in classifying counties as
high or as low risk. So far it looks as if it's working pretty well."
C(R.So.) "Fairly well" is the last word there. How much stronger is the
explanatory power of geological measurement when you have these two
variables instead of just one? We should be able to get a quantitative feel
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for how much we can improve our explanatory power when we consider both of
these variables instead of just one."
A(B.T.) "We do that under the slab. You take your grab measurement, we see
how pressure fields develope, and you're basically measuring permeability."
C(R.So.) "The goal would be to improve the quantitativeness of these
methods. The discussion in these last two hours has been non-
quantitative ."
A(A.T.) "The really missing variable, though, is where you are on the
coupling efficiency between the ground and the house."
C(R.So.) "The third element is obviously how leaky is the house boundary?"
C(A.T.) "We're going to come to a solution to the first two before we
figure out the third, I'm afraid."
C(D.S.) "Rich suggested that you needed winter and summer readings, some
indication of an annual kind of situation. In looking at the Canadian
survey, they only do summer measurements. They've come up with very low
levels of geometric means. They have no problem, by their definition. In
my opinion it is inadequate to make measurements in only one season".
C(A.C.) "In fact the highest level ever measured was found in June, closed
house, on a dining room table, when temperatures were in the eighties and
nineties, slab on grade house, a value well above 5000 pCi/L. The
measurement in the wintertime was only 2000 pCi/L.
C(A.T.) "That soil runs several hundred ppm of uranium as well."
C(A.C.) "In fact the gamma measurements in the backyard got as high as 120,
average at the four corners was about 80."
C.(T.T.) "I don't think we should overlook the value of gamma in a quick
screening method either, I mean an on-foot micro-R-meter kind of survey. If
you've got high soil gas you're going to see the bismuth gamma, you're going
to see elevated background in a hot spot. If you've got gamma in any
amount, you can bet that you'll find high radon in that area."
C(M.K.) "But if you have low gamma, you still can't tell that you don't
have a problem."
C(T.T.) "Yes, but it will tell you right away where your real hot spots
are. I've never seen an extremely hot house that didn't have a significant
gamma radiation level associated with it. I came out of the Watras's house
in my sport coat, and about 30 minutes later down in the valley I measured
about 60 micro-R per hour, background was twelve to fifteen. It's a good
quick screening tool to find the hot spots."
C(M.M.) "I've seen a fair amount of correlation between gamma and radon
levels, and the correlation is better at high levels. The gamma seems to
indicate the high level houses a lot better. Gamma seems to me like a
useful tool for identifying those very high level houses. It may not be as
useful for those houses which range in the 10, 20 or 50 pCi/L levels."
C(A.S.) "No, I would say that it is the other way around. Gamma may be
useful for identifying regions, but as for identifying individual places
(unless they are contaminated) it is not very useful."
Q(M.M.) "You're saying that gamma could grossly identify a region, but
probably would not identify a single house?"
A(A.S.) "Yes, particularly when we're dealing with these very high houses.
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Let me say that it seems insufficiently predictive for me to suggest it as a
general rule."
C(T.T.) "Let me use an example to help me with my argument. We've got an
area in Edgemont, South Dakota, where none of the houses exceed 30 pCi/L
radon concentration. This was not the result of any mill tailings, but
rather, occurred naturally on the ridge where the houses are located. The
gamma is consistently 40% above normal background down along .the streak
where we've got these elevated houses. We're seeing the radon and the
Bismuth 214 in the soil gas in an equilibrium."
C(M.M.) "So here the gamma is identifying even lower-level houses."
C( ) "The question has to be phrased very carefully here: are we looking
for something to tell us not to put radon resistance into construction? Or
are we looking for something to tell us to be on our guard for extreme
problems after the fact? I see no evidence [that we've found] an.indicator
that says that one should not put in the radon-resistant construction. Yet
we see many indicators here that tell us that we may be risking a very high
house, and that we should be on our guard."
C(A.T.) "Let's take south New Jersey. It's in the Atlantic coastal plain,
there are rather few places where it would be reasonable to expect that
there would be course material to give you a permeability problem. The
uranium series activity in the ground is quite low. You might want to say,
'Look out, boys, look out for some ridges of gravel that we might find
sometimes; there you've got to take caution.' But otherwise this is an area
where radon-resistant construction should not be necessary 99% of the time.
The same thing goes for much of the outer coastal plain on the east coast.
You get down to the Carolinas, then you've got to start worrying about
Thoron. Unfortunately, the measurements being taken now do not detect
Thoron--not that they can't, but routinely they try to exclude Thoron from
consideration. I think that is going to be a mistake in some places."
C(T.B.) "If you get Thoron present in any large amount, you'll get a
background which will last longer, and I haven't seen that any place. "
C(A.T.) "Well, so far I haven't seen Thoron greater than 30% of the radon.
count. But there are some places where it may occur, there they're known.
C(M.M.) "Let's move on now to visual inspection and questionnaires, out of
the realm of source availability and into the realm of diagnostics. Visual
inspection and questionnaires: what information can we gain by simply
looking at the house and asking the home-owner questions about the house?
That will give us information which we'll later use in developing mitigation
techniques."
C(A.C.) "The LBL questionnaire which we were using both in New Jersey and
in other places consisted of five or six pages of questions. The surveys
simply give us a systematic way of looking at the most likely entry points
for.radon. Mary Cahill has made a few house visits with me, and I've walked
through a house, spent a half hour in the basement, gone upstairs and sat
down at the dining room table, and she was writing and I was helping. I can
answer 90% of the questions there without going and looking. The reason is
that I've been in enough houses and I've found enough cases where there are
obvious radon entry points that I know what to look for. The best thing
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you've got is your pair of eyes. You often run into things that you had no
way of predicting. We were walking through one house in New York when I saw
a block of wood lying on the floor. I kicked it and it didn't move. When I
picked it up I saw that it covered a hole in the slab. This was on an
asphalt tile floor, and the block of wood covered a cleanout plug for a
sewer line that went out to a septic system. The plug had never even been
caulked in, and the soil was showing. There was no way to look for this
sort of thing, it just happened to be there lying under a piece of wood.
You can see holes in the wall without any problem. As Terry said this
morning, if you can see dirt, you know you've got the potential for a
problem. But you've got to constantly be thinking of places where dirt
might be exposed, that you can't find. Arthur can tell you stories of floor
drains which looked absolutely innocuous, not at all like they could be
entry points for radon. After about a week of trying to find where that
last fifty picocuries of radon was coming from, he tested the floor drain,
and it was the floor drain without a trap, but drained to the surface behind
the house, not connected in any way to an entry route. However, when he
finally took his grab sample out of the floor drain that didn't have a trap,
and measured the velocity of flow in it, there was enough radon in the gas
coming out of the pipe to account for the level in the basement. There was
a perforated drain tile all the way around the footer, and where that drain
surface ran through or under the footer, they tied the drain tile into that
line, and ran it to the surface. That was a good collection system around
the house, the soil gas was coming up an innocuous line which had no
perforations in it. Because of the drain tile arrangement it was dumping
radon into the basement. It suddenly dawned on me a month ago that when I
built my own house, I ran my three basement drains to daylight, and one of
the three has never had any water in it. When I went out under the
foundation with it, I remembered that I tied my footer drains from all
around the house to that same kind of line, exactly what I'd seen in
Pennsylvania. There's a source you have to look hard for; there's no way to
know what is there. Even if someone had questioned me, I wouldn't have
noted it, because I wouldn't have thought of it. In fact, it didn't even
occur to me until a year after our visit to Pennsylvania."
C(A.S.) "Let me add to that. One home-owner told us there was no weeping
tile drain around the house. I suspect he may merely have had crushed stone
without."
C(A.C.) "Either way. There's some way that soil gas is getting in to that
pipe and coming in. It used to be very common to put drain tile around the
house, go in through the basement, and into the sewer line above the trap.
Then they made it illegal to put storm water in with sanitary water. When
you're looking at these houses, think of yourself as a gas, and look for any
holes you might get through.
Q(M.M.) "In talking with homeowners and making visual inspections, what
additional information could you gain for designing mitigation techniques
for that house?"
C(A.C.) "As far as I'm concerned, the longer the questionnaire, the better.
(laughter) This may come as somewhat of a surprise to your people, Mike,
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but I'd like to get that questionnaire down to two pages. The reason is
that I'll pick up most of these things, [that home-owners write on their
questionnaires] when I go through a house. But we have to think about the
new people just getting into the field, not just the experienced people
who've been through hundreds of houses."
Q(D.S.) "To put this in context, are you talking about a twenty- or thirty-
minute walk-through, or about something which has been categorized as coming
later, as part of the pre-mitigation surveys? At that point you need six-
or eight-page questionnaire, you need all the information down in a
systematic form."
A(M.M.) "I'm talking about a very cursory, preliminary visual observation
of the house, and questions that might be asked of the home-owner."
C(D.S.) "That's the sort of thing that states often do. When they think
they've got a problem, they'll visit the home and fill out a one- or two-
page questionnaire. But that has limited value."
Q(T.B.) "Is this a questionnaire that someone takes out and walks around
with, or one like those which Bernie Cohen sends out?"
A(M.M.) "This is a questionnaire like those which Bernie Cohen or the state
might send out. We're not into pre-mitigation diagnostics yet."
A(A.C.) "These one- to two-page questionnaires have got to be so simple and
explicit that even a home-owner who knows nothing about construction could
understand it. You've got to assume that he knows the difference between a
public sewer and a septic system, and that he knows whether he's on public
water or a well. These things are important in this first phase: whether
his house has a' crawl space, slab-on-grade, or basement, or some combination
of these; if he has a basement, whether it's block-wall or poured concrete.
These questions have to be phrased so that the average homeowner, who knows
nothing about house construction, will know what the question means and how
to answer it."
Q( ) "What is the value of this type of questionnaire?"
A(A.C.) "When we're going to do an additional research project in an area,
and we want to cover 20 to 30 houses, then we'd like to have 100 to 200
houses at the beginning to start sorting from. If we start out with 500 or
so, then we can sort those into categories based on their substructures, or
into other categories, so that we can aggregate like houses into study
groupings. However, such a questionnaire does not help in the general
mitigation effort.
C( ) "The point I was going to make is that the way houses are built no
two exactly alike, if the soil gas is the same underneath, it really doesn't
do you much good just to know the substructure of a house as far as telling
you whether you're going to have a radon problem. You've got to measure
anyway. At that point you've got to do a longer questionnnaire, of the type
done before mitigation."
C(M.M.) "So the information which is to be gained here is simply the type
house, slab-on-grade vs. crawl space or basement, and questions as simple as
the type of walls, i.e., concrete block vs. poured concrete."
C(A.C.) "What kind of sewer, what kind of water, type of fuel, type of air
circulation, which might tell you something about depressurization of the
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house."
Q(K.G.) "Isn't this the same idea that mitigators are already using when
they prequalify a house by asking a list of about 10 questions over the
telephone? This method has already been in use for several years."
C(T.T.) "There are about 10 key questions which really mean something to a
mitigator. I have an example here, a letter from a man in Silver Spring,
Maryland. I fixed his house 3500 miles away and asked him 10 questions. He
wrote me a thank-you letter saying "I got [the radon] down from 16.8 pCi/L
to 2.8 pCi/L, Thank you Mr. Tappan."
A(A.C.) "I did the same thing with someone in the western suburbs of
Chigago, who had 10 pCi/L in his house in October. He did nothing but seal
the basement. He called me back in January with 1.7 pCi/L."
C(M.M.) "We'll try to put those ten questions together and offer them as
information to the group. One final question: It's a reflective question.
When we're talking about a questionnaire, we have to be sure what its
purpose is. I think we've been discussing several different ones
simultaneously. The purpose of that ten-question questionnaire is to
determine whether there is any action which the home-owner can take, short
of calling in professional diagnosticians or a mitigation team. There are
five or six questions which you can identify, so you know if there is
anything the homeowner can try. Once we get beyond that questionnaire, the
questionnaire in the next level is much shorter. If the home-owner has
confirmed the measurements, or has tried sealant (which is generally what
we're talking about here), the next questionnaire simply askes the name,
address, phone number, and the date on which they are available. Any other
questions are really placebos, to show that you know your stuff and are
concerned about their house."
Q(M.M.) "This leads us to] the determination of radon concentrations in
different zones of the house.... Another thing I'd like to touch on is the
status of our scientific knowledge, our need for additional research: do we
feel we've reached a point where we can define the topics we've discussed
this morning? I'll let Wayne open that one up."
C(W.L.) "Let me pose one question for thought over coffee break. I come
from a side of DOE which has been concerned with basic research. Until this
morning I was thinking that we were going to have to do some detailed
geological studies to develop better predictive models on a regional basis,
to try to understand why certain mitigation techniques are effective; to
understand all the factors which determine radon entry rate, so that we
really have a firm scientific basis for making generalizations from the
experience we gain in the field. However, the message I've gotten today is
a little bit of a surprise to me. What I seem to be hearing is the fact
that we have already developed the kind of qualitative understanding we need
to be effective mitigators on a very broad basis, even though we can't put
all the factors important in defining radon entry together into a coherent
equation. I was very impressed by the success one speaker had, based on a
very limited approach to the problem. If that is true generally, then
perhaps there are just a very few questions on which we should focus our
attention. That is, perhaps we need not develop a radically more detailed
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scientific understanding. Perhaps we are already where we should be."
C(A.T.) "There are 79 million more houses, aren't there?" (laughter)
Q(L.K.) "One thing which we haven't discussed, which affects your panel and
the panel on post-mitigation diagnostics: how well we can relate a
measurement which we do either before or after the mitigation to the annual
average? This has certainly been one of the concerns in the houses in
Clinton, and when you get a year's worth of data those houses are probably
going to be under 4 pCi/L in an annual average. They're not below 4 now so
you can't really say that they are successful. I think that one has to be
careful that annual average exposure is really the number, and not the
single measurement in the basement."
C(T.T.) "We have tried passive mitigation systems. In one case the levels
stayed low to December when we hit a spike and we put fans in the exaust
stacks. We probably overreacted and we would have been o.k. on an annual
average."
C(M.M.) "So we realize that we need additional information. There are
studies going on right now to help us translate fairly short-term
measuremtns made under different conditions and at different times of the
year to that annual average. Our goal is to keep the annual average below
some given number."
C(L.K.) "So the groups who mitigate in the summer must know how low they
have to get [the radon levels] so that it will stand up in the winter [for
the yearly average]. When you're mitigating in the winter, you don't
necessarily have to constantly stay below 4 [pCi/L].
C(R.S.) "But it's the real-estate market which is driving a lot of
mitigation."
C(L.K.) "But if we have the data to back it up, to show that those numbers
mean something... We can't tell them anything now based on one measurement,
without an annual average."
C( ) "If you hire me to do a mitigation job, and if I bring it down from
200 to 8 PCi/L, and if your house is on the market, is that going to satisfy
you? "
C(A.C.) "They won't sell the house."
C( ) That's right, and 65 to 70 percent of the mitigation in this state
being driven that way. It's very difficult to get that point about the
annual average across to the home-owner, especially when dollars and cents
are involved."
C(M.M.) "Those are the facts of the real-estate market, and I've had to
deal with it too. Thank you all, that ends this session."
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Phase II. WORKSHOP DISCUSSIONS
PRE-MITIGATION DIAGNOSTICS - L. M. Hubbard, Chairman
C(L.H.) "First I would like to go over the order of the topics and the
distinctions we will make between research and "real world" applications of
diagnostics. Questions submitted ask what are the answers we are getting
from the measurements we have been making over the past few years?
Availability of the equipment; how easy is it to implement; and what are the
costs involved are some of the other questions. A good example of how
research approaches can be applied in the field was given by David Saum
earlier in the workshop -- looking at subslab ventilation diagnostics. In
what percentage of homes will SSV work successfully is another question to
be answered. Questions about some of the most useful diagnostics, grab
samples, both ambient and depressurized with a blower door, are often asked.
Communication under the slab is a question that has already received
considerable attention so perhaps it doesn't need much more discussion here.
Tracer gas measurements, differential'pressure measurements, soil gas flux
measurements are all topics needing discussion. One question that has been
asked is how can stack pressure be measured -- hopefully we will have time
to discuss that question. Are diagnostics cost effective? I would like to
hear from the mitigators on that question. Also, do the seasonal variations
matter? I would like to begin with a few words from Wayne Lowder on
research versus the "real world" diagnostics."
C(W.L.) "First of all I have been chastized by all the DOE contractors
during the intermission for my remarks. However, my statement was just to
stimulate discussion. (Laughter) There is a very important distinction to be
made concerning the real world application of our current state of knowledge
which derives from the research over the past few years. What I am hearing
today is that this research has been very successful in pointing out the
significant parameters: what should we be looking at and how we can simplify
the diagnostics for real world applications. As we assemble many case
studies of success, mitigating under some degree of ignorance, we need a
scientific knowledge base in order to understand why we are successful in
particular cases. In this way we can, with some degree of confidence, move
on to improved procedures for a variety of circumstances. There is clearly
a need for research, the EPA field demonstration program is a prime example,
especially the study in New Jersey, which is a combination of the practical
and the research aspect* of mitigation and diagnostics. This is a very
important effort.
I would like to stimulate the mitigators here to probe the questions --
do you feel confident that you will continue to be successful and what do
you think are the needs for better information from the scientific
community?"
Q(L.H.) " What diagnostics are useful to understand the radon mechanisms?"
A(W.L.) "We are really zeroing in on those factors in the environment that
are'relevant to radon entry rates in housing. The question of radon in soil
gas is extremely important, since it surrounds the house, and supplied the
"available radon". Its the soil gas that transports the radon into our
houses and is the source for the indoor exposure. Permeability is the
property of the soil that tells us, together with the differential pressure,
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the rate of soil gas transport. Maybe in a way we ought to define an
idealized situation which will represent a figure of merit - a model house
(or several houses) with properties that are well defined so that when you
have a pressure difference across the envelope and you have certain defined
soil characteristics and a level of radon in the soil gas, you have now
defined the "source term" in this idealized situation. Whatever number you
get is representative of a particular site even though it doesn't represent
a real house, it does relate to the idealized set of circumstances. The
real problem is there are so many variables, particularly within the house
itself, you clearly can't develop a model (with a finite number of
measurements at the site) that will define the radon entry rate at any
particular time. So really it comes down to the fact that we have to
understand the mechanisms involved and generalize from a particular case."
C(L.H.) "Let's hear from the mitigators".
C(R.Si) "What I have been hearing is that SSV achieves a high degree of
success but that it is highly dependent on the conditions under the slab.
What we are then dealing with is a very small percentage of houses where SSV
doesn't work because of soil conditions. We are looking for an amount of
suction that is going to overcome the radon flow into the house and redirect
that gas flow. Some of the things we want to look at are the necessary
forces to just what is necessary to remove the radon. Another item would be
aimed at house without good communication under the slab where using a
"small well", you might short-circuit the radon before it reaches the slab.
Q(L.H.) "What percentage of houses are not cured using SSV?"
A(R.Si.) "The percentage we have found is very small, i.e., only one or two
houses out of a hundred. Even then it is often a question of fine tuning.
Using dampers in the mitigation piping allows one to increase the suction
where it is most needed. For example, with slab-on-grade it might not need
as much subslab ventilation because of settlement in the area along the
common wall."
Q(L.H.) "Do you use premitigation diagnostics?"
A(R.Si.) "The premitigation diagnostics are limited to a communications
test, taking into account all the obvious things that have to be dealt with,
working toward a mitigation strategy. In the case of limited soil porosity
we would employ a collection pit area, something we have done for the
Piedmont study. The number of pits would be related to the basement
geometry and soil porosity."
Q(A.C.) "How big is the pit?"
A(R.Si) "Typically its a two foot cube, but we may include perforated walls
and base to increase the effective volume to help draw in the radon gas."
Q(L.H.) "Bill, how much premitigation diagnostics are you using?"
A(W.B.) "Often it is just a walk through where we anticipate porous soils.
In the early days, we would have used an air-to-air heat exchanger for radon
mitigation but now that has become a less attractive option, as we now are
removing those units and replacing them with subslab units."
Q(L'.H.) "Do you use grab samples in your work?"
A(W.B.) "I do use grab samples occasionally to test for hot spots. If
there is a question of communication under the slab I do use the vacuum
test. That's really the most important test where I use the Magnehelic
gauge to get actual pressures. Using smoke, sometimes it will not go down
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the hole even when you can get a gauge reading (sometimes after 15 to 30
seconds) with marginal communication. At other times the opposite is true,
so you should use both methods."
C(A.S.) "Let me comment on the word "diagnostics". It is being used
currently as being all things to all people. If we follow the medical
theme, we know what disease these houses are suffereing from, it is
"radonitis". It is "diagnosed" by making one measurement to show radon
levels are elevated. The subsequent investigation that takes place is
"pathology". We are looking at the approximate cause, but knowing the
causes of a disease may provide no help in the treatment. Our scientific
friends are involved in "pathological research". Mitigators are involved in
"therapy planning". There is a sharp distinction between knowing the
pathology and determining what can be really helpful. Subslab ventilation
could be viewed as the penicillin of the radon world. If we can achieve
soil depressurization we know the problem will go away. We don't need to
know if people are running dryers or what the pressure deficit is in the
house."
C(W.L.) "You don't even need to know where the hot spots are."
C(A.S.) "That's right. You probably don't even have to know much about the
house."
C(R.Si.) "Probably the most time consuming item is how to get the exhaust
pipe up to the roof."
C(D.Sa) "I agree with some of these statements, but its hard to say what
percentage of the time you will get results by slapping something into the
nearest convenient place. Perhaps 50% of the time. We certainly agree
diagnostics aren't always absolutely necessary. I would like to go back one
step. There seems to be some question what SSV is actually doing and what
is its active mode that is actually solving the problem. I claim that
suction on these surfaces prevents radon from entering. There seems to be
some question if its the air movement that has something to do with this. I
claim that if we could do a perfect sealing job and no soil gas came in from
the upper surface of the soil that would be fine and that suction itself,
with limited air flow, would be the goal".
C(L.H.) "I thougt the question was flow out of the mitigation system?"
C(D.Sa) "I don't think we have even really decided how radon comes into the
house when good sealing is done. I am finding it's pressure driven flow
through concrete therefore all my actions are to get as low an airflow as
possible and as high a suction as possible. There are some people here that
don't think that's right."
Q(A.C.) "We did have a little discussion during the break. But first I
would like to ask if there is any significant passage of soil gas or radon
through four inches of concrete, that has no cracks in it?"
A(D.Sa.) "I have made such flux measurements. Placing a box over what
appeared to be crack-free concrete I noticed a build up of radon in the
winter in the box, but in the summer time, with no pressure differential,
the' radon was not present."
A(B.T.) "In our flux measurements on concrete blocks and poured walls and
floors, if you do the calculation, you can only account for a fwew percent
of the indoor radon levels. These measurements would account for diffusion
and microconvection and it is not enought to account for the indoor levels
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that we see. A fine network of cxracks may contribute to the problem but
will not be sufficient."
Q(D.Sa.) "There is a bit of contradiction here - why can't we seal and
achieve our goals?"
A(T.B.) "We are digressing into mitigation. Knowing where it comes from is
important. My experience has been with doing subslab suction with one
pressure point in the corner. The experiment had other points open at the
other sie of the slab, hoping to indues cross flow assuming that was
important. The more we sealed the better reductions in radon concentration
we achieved. Thus we moved to higher suction under the slab and less
airflow."
A second example is from one of the Clinton houses with a dirt floor
crawlspace. We placed perforated PVC pipe in a grid on the floor and sealed
the floor with a heavy polyethylene film - a that is transparent to radon by
diffusion. Then we applied suction to the PVC pipe with complete success -
the radon did not penetrate the plastic.
General Discussion: (T.T. D.Sa. R.S., T.B., etc.) The goal is to reverse
the pressure gradient, flow is not the important feature rather it is the
fact that flow is from the substructure into the soil. The establishment of
a slight negative pressure is all that is needed.
C(A.T.) "NBS has been trying to develop a portable radon source using a
thickness of polyethylene where half the radon decays prior to passage
through the film (13 to 16 mills). Ron Colley and Robin Hutchinson are the
people to contact."
C(T.T.) "We use radium ore inside a plastic covered bucket as a method for
evaluating materials. It's amazing how many plastic materials that radon
moves through."
C(T.B.) "Diagnostics reveal how good the communication is under the slab.
The presence of a good gravel base or soil separated from the slab means
that one can often be successful with SSV using a single suction point even
on the basement perimeter. In other cases, spotty suction is evidenced (in
one direction for example) and in clay there may be no influence beyond the
suction point. Powdered soils may indicate little communication using the
vacuum cleaner technique yet frean may pass through them. SSV systems thus
may still prove successful. At the fine end of the soil particle size
range, basement walls may become more important as a radon source. Freon is
very slippery and can move quickly through even fine soils with the suction
in place."
C(R.S.) "One justification for further research is that all mitigators
indicated they have installed systems that don't work the first time."
Q(L.H.) "Where do blower doors play a diagnostic role? The usefulness of
blower doors relates directly to the application. If SSV doesn't work, then
the BD may have application to radon mitigation basement pressurization,
heat recover ventilation, or subslab pressurization."
A(R.Si) "We used blower doors for subslab system evaluation but we have
abandoned that approach. The question is where do you use the blower door?
We have a high confidence that with one hour of diagnostics we can tell
whether SSV systems will work, without use of a blower door. If SSV won't
work, then what is the next best mitigation method? More direction on that
point may involve the blower door. Heat recovery ventilators, basement
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pressurization, subslab pressurization are some of the candidates for the
second best strategies."
A(T.B.) "The blower door is useful for sizing the fan for pressurizing the
basement. The fan must be small enough so that a large energy penalty won't
be paid (same range as normal air infiltration, i.e., less than 300 cfm).
One also wants to avoid too much suction upstairs which can cause problems
in down drafting combustion appliances. Sealing between basement and
upstairs reduces the required air flows."
A(I.N.) "The blower door applied to SSV system diagnostics has proven to be
helpful to evaluate basements under extreme conditions, e.g., simulating
winter stack effect conditions to make certain SSV will be effective
throughout the year. We have examples where systems failed under winter
conditions but were fine in the summer."
General Discussion: Concerns were expressed as to what level of
depressurization assured that the SSV systems would work for all seasons. A
degree of consensus was arrived at. The house is a box, with the volume
under the slab another box. The important point is that there are pressures
in both boxes. A rule of thumb such as pressure differences at least 0.015
to 0.03 inches of water (4-8 Pascals) would appear sufficient for SSV
success."
C(K.G.) "Movement of the neutral plane by controlling air leakage sites
(via sealing) of the upper portions of the house can also limit the stack
effect and thus make the radon problem less severe (and the SSV requirements
less stringent)."
Q(L.H.) "Again do we have any additional answers to the question: Is the BD
useful in evaluating SSV systems?
A(M.Me.) "We haven't been able to make the blower door do the SSV
diagnostics job, but the "blower floor" has applications in this area.
What about the use of the blower door to assess leakage areas for HRV's?"
A(A.S.) "The best application of HRV's comes as a result of changing the
distribution of the air flows in the house and not the general level of
ventilation achieved. Dilution effects are limited to two or three times
normal ventilation rates. By sending the air upstairs, much more can be
achieved. BD measurements can help resolve air leakage for different zones
and thus help the mitigator make the right decisions."
Q(L.H.) "Taking grab samples around substructure under different
conditions (ambient, pressurized, etc.) is one diagnostic approach. How
useful are these techniques based upon recent research?"
A(B.T.) "Depressurizing, and taking grab samples does seem to bring about
radon movement similar to winter heating season conditions. There is a
question as to whether this would be true in all homes. There are also
changes in the radon levels in the soil to confound the issue."
A(R.S.) "Pressure differences are due to stack, wind and appliances. Wind
pressures are directional, thus influencing the soil on different sides of
the house. Ventilating the soil is also possible due to the wind. Using a
negative 10 Pa standard test applies a 'research base'. Measurements on
walls, floors and piping in the mitigation system add to our knowledge."
Q(B.T.) "Grab sampling is a integral part of the radon research; do
commercial mitigators see this as a useful diagnostic approach?"
Q(D.H.) "Isn't the depressurized condition for grab sampling the more
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useful approach and should this be the appropriate standard? Remember it
again takes time to reach equilibrium after the start of depressurization."
C(K.G.) "Clearly the most recently tested house in the Piedmont Study
showed combinations of wind pressure and return duct leakage that caused
negative 10 Pa basement readings."
Q(D.Sa.) "What about the situation of entirely different results when
applying the negative 10 Pa to two houses? One shows a radon concentration
dropping to zero; the other a large increase in radon levels."
A(D.H.) "What is entering the picture is the radon source characteristics.
In one case you have a condition of a limited radon source which is rapidly
depleted. In the other case you have a large radon source where the soil
gas has reasonable transport into the house.
C(A.T.) "The vagaries of different soils immediately around the house, the
location of openings through the basement walls, and the effect of freezing
soil cover in winter may all influence the amount of radon entering the
house. Also local freezing could plug off leakage sites."
Q(D.S.) "Hollow block wall convective loop air movements were evident in
some of the testing -- could we hear more on that subject?"
A(B.T) "Again depending on the air movement in the blocks, outside air
ingestion can mean a local dilution and reduced radon concentration. In
other situations more radon was drawn from the soil and concentrations rose
inside the blocks during depressurization."
C( ) "At this point the use of negative 10 Pa as a standard diagnostic
procedure is inconclusive, although it would appear to be useful much of the
time."
Q(D.Sa.) "How good are grab samples under ambient conditions? Although I
have only been in the mitigation business for seven months I have assumed
grab samples from under the slab to be relatively invariant over the year.
Sampling in walls has been limited in our houses."
A( ) "I have concluded that grab or continuous sampling under the slab is
invaluable since one must match the final pressure field to cover the high
level radon sources. Relative distributions are basic, and if these were
changing seasonally this would erode confidence in the approach."
A(B.T.) "In the seven LBL homes we have the ability to measure subslab
radon concentrations when mitigation systems are turned off as well as the
continuous measurements in the control house. Variations are observed."
C(L.H.) "Variations over 24 hours are another problem with grab samples as
well as spacial variations."
C(R.S.) "Less diurnal variation is found in the radon concentration under
the slab than in the basement, for example. For most houses, I don't
believe grab samples are very useful. However, with more difficult
situations, e.g., subslab lacking communication, grab samples may answer
vital questions."
C(L.H.) "With mitigation systems in place, continuous readings illustrate
SSV altering concentrations in the wall when they are turned on because of
communication between wall and subslab and sweeping of basement or outside
air into the wall dilutes what was the higher radon concentration zone."
Q(L.H.) "Tracer gas methods, where do they fit in?"
A(T.B.) "One application is the use of freon. The freon tracer moves under
the footer to indicate drainage paths."
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A(B.T.) "In Portland tests, tracer gas (SF6) was injected in the yard (via
probes at different distances and depths) and monitored continually for the
level of buildup in the house. Transit times were measured, coupled with a
pressure field map (depressurized the house and looked at pressures and
probe points around the yard) to see if gas movement correlated with the
pressure fields."
A(T.T.) "We have traced air flows over an entire slab using freon tracer
looking at details of the flow paths."
C(D.S.) "There is a question whether tracer gas should be reserved for
problem cases and not used as a premitigation diagnostic tool."
Perfluorcarbon tracers are another candidate for tracer methods."
Q(R.S.) "SSV does seem to work in many situations. What concerns me is
whether these systems continue to perform over the long haul. Will the
systems receive proper maintenance? We are mitigating hot houses with
mechanical systems --is this the way to proceed in the long haul?"
C(D.S.) "Durability is an important consideration, partly the reason the
diagnostic list was more complete is that we need backup strategies. The
government and other interests represented here can't just say that we don't
know what to do for 10 of 50 houses based on public health. We need backup
mitigation approaches, and backup diagnostics. That is one reason we have
been discussing blower doors. What are those other options and how are they
going to work? Even though SSV appears to offer an acceptable solution in a
high percentage of homes, that is not enough. We need other options. Over
the 20 year time frame we must consider cost effectiveness. Once we have
defined cost effectiveness we must fill in some of the options that have
only been discussed briefly."
C(A.C.) "What we are looking for is a fail safe technique. It doesn't
matter if it.is mechanical or not, but one must know when it is working. In
the Washington, DC area one group is using a five dollar switch to indicate
when suction is lost and a warming light will be activated where the
homeowner can see it -- you do not have to go down and read a gauge.
Remember a passive system can be overwhelmed and the homeowner not even know
it is failing to do the job."
Q(T.B.) "When do you know when to use a SSV system? What must we know
about the soil? A finger of sand that brings the radon to the house is one
example (in my experience, three out of 50 houses exhibited this problem).
Sensitivity studies are needed based on soil conditions and where the house
is situated. Such a study could be very helpful to mitigators. Those in
geology could supply source terms, those in soils could provide permeability
factors and those in building science could supply information on leakage
area locations and mechanical equipment factors which influence the
pressures. There is a lot of work to be done in this area."
C(A.C.) "Considering the kind of houses, we have mostly been discussing
houses with basements which represent approximately 50% of the nationwide
housing stock, with 35% slab on grade and 15% crawlspace. But here in New
Jersey 50% are crawlspace construction. In some states 70% are crawlspace
houses, but we haven't even started on that part of the radon problem
concerning dirt floor construction."
Q(K.G.) "Maintenance of fan systems would appear to be a problem since
homeowners tend to ignore maintenance issues. The fans are often in
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difficult-to-service locations and the manufacturers cite only a three-year
guaranteed lifetime. What is the cost for replacement at a homeowner's
expenses -- is it several hundred dollars?"
C( ) "Although the guarantee is for three years, the service life is 20
years. The average life expectancy for this type fan is approximately 15
years."
C(K.G.) "I would question long lifetime claims when the fan is working in
an environment of high moisture and problems generated by other soil
ingredients".
C(D.S.) "The Canadians have experienced a five percent failure rate in 24
months on their fans."
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Phase III - WORKSHOP DISCUSSIONS
MITIGATION INSTALLATION DIAGNOSTICS - M. Osborne, Chairman
C(M.O.) "This particular session starts with the premise that we have a
mitigation device in place. Our emphasis will be on four different
mitigation approaches and the related diagnostics. We will limit discussion
to the time period when the system is being installed without a post
mitigation knowledge of what radon concentration reduction has been
achieved. Our question to answer is: How well is the mitigation system
operating? The four areas we will be considering are: sealing, dilution by
increased ventilation, basement pressurization and soil depressurization."
C(A.S.) "Regarding diagnostics and the sealing approach, caulking isn't
sealing. The objective of sealing is to increase the resistance of the
house structure to soil gas passage so that it is much higher than the
resistance of the soil. The open area in many houses is considerable, e.g.,
some southern houses have leakage areas equivalent to several windows being
open. In that case, the soil is the more resistant element in the flow
path."
"In Canada, a program to establish the leakage area goals indicated
that one square centimeter of leakage area was all that could be tolerated
for the approach to work. This is a very nonlinear situation, with major
improvements in soil gas flow reduction only evident when a very tight
system is achieved. Epoxies often don't adhere properly. All the sealing
work must be of high quality; excellent surface work must be of high
quality; excellent surface preparation is key. Proper bonding to the
surroundings is vital. Sealing has been tried and found difficult
especially in retrofit situations. In new construction one can design a
hollow where you can pour the sealant between building components. In
retrofit, a jackhammer may be needed to form the hollow."
Q(M.O.) "How do you test to make sure the sealing was done properly?"
A(A.S.) "First, it is recommended that you use an experienced team that
employs common sense in the sealant installation. Secondly, use sealants
that are the most forgiving. We have surveyed a number of sealants, and our
favorite was a solvent-hardening rubberized asphalt. The reason is that it
was much more tolerant of the lack of cleanliness in the application. Other
sealants required primers, but the recommended sealant formed its own
primer. These sealing systems were tested in the lab using concrete blocks
and then the bonds were tested for flexibility."
A(T.T.) " We ran a series of tests in the late sixty's using huge stock
watering troughs, and uranium source material for the radon generation.
Concrete, membranes, and paints were evaluated at Colorado State. We found
extreme variation because of bond problems and seam sealing. A path of
least resistance is followed by the soil gas/radon and small leaks were all
that were needed for failure. Quality control was really the only
diagnostic. "Holding the contractor's hand" to make certain the job was
done right, according to specifications was necessary until they really
understood what was required."
Q(M.O.) "What diagnostic approaches are appropriate?"
A(T.T.) "One approach is to use flux measurements to check the before and
after readings. Even pinhole leaks would indicate degradation of the seal
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using this approach."
A(A.S.) "These are basically water proofing materials, trowled on or poured
into joints, and they work."
A(A.T.) "Bureau of Mines work on sealants should also be cited. Sealing
studies by John Franklin and Bob Bates of the Spokane Bureau of Mines Office
(1976-1982 literature) dealt with sealing mine walls and pinhole leaks."
C( ) "Continuous readout equipment looking for freon leakage is an example
of one diagnostic approach."
C(A.S.) "Radon may be its own tracer to check for leaks."
C(M.O.) "The next topic is radon dilution by increased ventilation."
C(B.W.) "First I should state that the walk through inspection is important
to check for items that are critical to any ventilation system, not just
heat recover ventilators (HRV) which I will be discussing. One important
point is the location of air intake and exhaust to eliminate problems of
exhaust entrainment and poor ventilation effectiveness There are
installation instructions available for HRVS to aid the
contractor/mitigator. One caution is the case where there is a SSV system
also present, the intake of the HRV must be away from the SSV radon-laden
exhaust. Also, the HRV intake must not be located close to the ground,
where leaves and debris can be picked up, blocking the intake and
unbalancing the system."
ABOUT TEN MINUTES OF THE DISCUSSION WAS LIST HERE IN THE TAPED VERSION
C(B.W.) " Obviously when you do plugged flows it's nice to take
your exhaust from the area of highest source strength. That can be a useful
tool."
C(M.O.) "Let me open things up now in this -area, and see if there are any
other comments. Please try to address diagnostics."
Q(K.G.) "We've seen a lot of furnaces out there which are depressurizing
basements. What effect does that have on the balance of an HRV (Heat
Recovery Ventilator)? Do you check that after installation?"
A(B.W.) "We can't, because without some kind of automatic feedback
mechanism you can't accomadate the needs of the other appliances. The
industry response would be that they are not responsible for make-up air for
the furnace; that should be provided."
C(A.C.) "But I think the important question here is not the make-up air,
but rather, the effect of the circulating system, the depressurization of
the basement from the pickup of return air. I've spoken with with one HVAC
man who was a real authority in the field, and he said that he had seen as
high as 250 cfm picked up in crawl spaces, measured in the heating system.
The difference is when the fan is on and off. It doesn't have anything to
do with combustion. We've seen places where we've increased tremendously
the inflow through cracks by turning the furnace fan off upstairs. It's a
tremendous difference, and it will affect your balance on the HRV and
everything."
A(B-.W.) "It will. The answer which we've given is that at least with the
HRV in there, you've got a couple big holes in the wall, which help to
moderate the negative pressure generated by the circulating or the
combustion air, what. The negative pressure generated tends to increase the
flow in the supply side, and decrease the flow in the exhaust side. It
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helps, but it will tend to throw it out of balance."
Q(D.S.) "What are the duct flow measurements you talked about? Wouldn't
they see that difference if there were an interaction?"
A(B.W.) "Yes, they could. That's something we haven't done."
Q(G.F.) "Bede, have you done any comparison diagnostically with respect to
using a continuous working level monitor versus a continuous gas monitor?
What are the differences [one gets] in the end results?"
A(B.W.) "EPA actually did some side-by-side measurements of the continuous
working level and the continuous gas monitors in one of the houses where we
had a heat recovery ventilator and turned it off and on. They are very
comparable. But as we always saw in doing our post-mitigation diagnostics,
the percentage decrease in the working levels is greater that the decrease
in the radon gas."
Q( ) "I don't know how [big an] effect it would be for the small ducts,
but when you're dealing with large industrial ducts, in terms of locating
your traversing point, if you get it at an elbow point and count about one
duct diameter.down, you essentially constrain the flow very nicely. So, you
can do a single plane traverse simply because you tend to get it all in one
smooth flow that's due to the changing that you're doing on it. As you go
across the plane, you may take more points, you don't do the normal type of
traversing where you just do a 3 or 4 points; you have to do quite a few.
But that does become a pretty good place to put one. And there were single
plane averaging pitot tubes, the brand name used industrially was
'Anubar'that is used industrially, that you can locate some place like that
without having to worry about the grid flow. These things tend to have only
one grid that they use, and you may have to adjust it to a finer grid scale
when you're trying to constrain it to flow around an elbow. But it can give
you a good, firm fixed flow point.
C(T.Mi) "I was going to mention that we're not really dealing with crawl-
space houses in terms of the diagnostics dicussions we've been having. But
some of the work we've done indicates that in the crawl space the
communication between the duct work, particularly when it penetrates the
crawl space in many places in the house, is just incredibly good. That's
one of the simplest diagnostics one is going to have to do in dealing with a
crawlspace house. A simple tracer-gas measurement can be used to tell what
the communication between the crawlspace and the indoors is, with HVAC on
and off."
Q(A.S.) "If it's good, why do you need to measure it?"
A(T.M.) "To get some indication of how good it is."
C(T.T.) "My experience in installing any kind of dilution system, heat
recovery or whatever, is that there are a couple of very helpful diagnostic
tools. One is the radon profile, where you have a concentration gradient
and you know where you're highest areas are in the house."
C(M.O) "Let me say that most of the radon measurement things are going to
be covered in the next session."
C(D'.S.) "The radon profile that you're talking about is actually part of
the installation. It's like your suggestion about having a radon monitor,
you would then see what the best configuration is."
C(T.T.) "The second important thing in installation is that if you're able
to flush the house out, and get it essentially to background, by use of a
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breeze-box fan or whatever, and you can determine the in-growth rate of the
radon into your home, you'll find through tests and a very simple formula,
that it's about 0.8 of a cfm per picoCurie liter hour in-growth into the
house it takes to dilute it to background and keep the house at that
concentration. There's a direct relationship between the in-growth rate of
radon into the home vs how much dilution air it takes to keep that
concentration."
C(M.O). "Let's move on to talk about basement pressurization."
C(1.N.) "Here we are dealing with the mitigation installation and
diagnostics, and I'm assuming that everything has been diagnosed so that you
have a specified, reasonable pressurization system. Let me just back up a
little bit: a few things are required for a sensible pressurization system.
The basement should be well separated from the upstairs. There should not
be any combustion appliances in the upstairs, lest you increase the chance
of backdrafting. You're more likely to be successful in pressurization if
you don't have a forced-air system, although there are instances when
pressurization will work even with a forced-air system. So, assuming that
your house meets these conditions and you've specified a pressurization
technique, let's go back now to where we are doing the mitigation
installation diagnostics. The first thing to check, of course, is whether
the pressure difference that you measured for the cfm with the blower-door
(which Terry described previously) is in fact what you're reproducing this
the actual installation. Instead of using the blower door now, the blower
door fan where you continually vary the pressure and the cfm, now you have a
fan with one speed or it could be a variable speed. Are you producing the
pressure differences you expect with the blower-door measurements? So, you
need to take a pressure-difference measurement between upstairs and
downstairs, and check the flow on the fan. Then you need to go into the
basement, and just as in the pre-mitigation diagnostics, check with a smoke
pencil to see whether smoke is going into the cracks at that pressure
difference. You have to check to see what the communication is between
upstairs and downstairs. You would have specified that the major openings
between upstairs and downstairs be sealed. This would alter the
characteristics of the pressure difference and the airflow, so if there were
large openings between upstairs and downstairs that had been sealed, then
less airflow would be necessary. You could even turn the fan down to a
lower speed to create the same pressure difference you were obtaining using
the blower door measurements. There may be some obvious cracks or holes
between the upstairs and downstairs which are still present. In all radon
installations it's best to see whether there are cracks and holes in the
basement, and this also might change the characteristics of the fan and the
pressure difference that you measured using the blower door. The other
things that you should check are the openings between the basement and the
outside, for example, if there is a door that goes to the outside that is
very leaky, windows which go from the basement to the outside. These should
have been sealed up correctly during the installation of the pressurization
system. You should go upstairs and check to see that there is no
downdrafting in any combustion appliance, e.g stoves, wood stoves,
fireplaces. Of course this is very difficult to do in the summer. This
brings up an important point: if some of your pre-mitigation diagnostics
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with the blower door were done during the winter season, and the actual
installation was done later on in the year, it may be difficult to find out
what this system's characteristics will be in the next heating season. It
may be necessary to come back during the next heating season to see whether
everything is working as you thought it should. One of those things is the
operation of the stoves and appliances in the upper floors. Pressurizing
the basement should increase the effectiveness of the flues and combustion
appliances in the basement area. There may be an unexpected interaction
with the heating system. Those things also should be looked at. The
location of the fan, where it is drawing air from upstairs, is very
critical, and should be discussed with the homeowner. Sometimes a house may
have a laundry shoot, or there may be a natural place where a fan can be
placed. That might be good from the homeowner's point of view, because it
is out of the way, but this may not be a good idea from the standpoint of
system performance. For example,if you use a laundry shoot that goes up
into the second floor, you're actually increasing the stack effect on the
whole house. You may, in effect, be drawing more air from the basement to
the upstairs. Try to locate the intake of the fan at a lower level. A
closet also is probably not the ideal location from the standpoint of system
performance, but is good from the homeowner's standpoint. Sometimes these
things change when the contractor comes in and discusses these things with
the homeowner.
Q(M.O.) "Could you address the question of moisture? There seems to be a
potential problem of frosting and rotting out of the rim joists. [Do you
know of] anything you can do to evaluate that; any diagnostic technique
which you could use to see if that's going to be a problem?"
A(I.N.) "You're talking about forcing moisture out. If smoke sticks is the
usual diagnostic tool to see whether there are large leaks into that rim
joist area."
Q(D.S.) "Isn't that part of post-mitigation, because you're looking for
some actual effects that might start to show up?
A(M.O.) "Maybe not. If at the time you're doing this there is something
you could do to find out whether there is a significant leakage, or whether
there is a moisture problem."
C(D.S.) "Along these lines, if it's the pressurization, what is the flow
rate, just what are we actually moving out? You could do a calculation to
find that out if you knew the exit rate of the air, the moisture content --
maybe moisture content is an important variable, and should be covered in
pre-mitigation."
C(B.T.) "I have several comments to make. One is on the moisture. First
of all, in the homes in Spokane WA, we have not observed a change in the
whole-house ventilation rate after we've done this. We've increased the
basement ventilation rate considerably, in some cases we've doubled or
tripled it. The air has to leave the house somehow, and under natural
conditions it leaves the house near the top. In the climates typically
found in the U.S., we haven't had problems with rotting around the exit
points. We might expect to see moisture from condensation collecting and
causing rotting in structural members in the basement. But I don't know
whether it would be any worse than seeing it at the top of the structure
under natural exfiltrating conditions."
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C(T.B.) "We have seen that frequently, under natural conditions."
C(D.Sa.) "I don't think that is necessarily true, because you're looking
for a condensing surface, a cold surface against which this warm air will be
pushed. Up in the attic, there is no condensing surface; there you've got
the attic ceiling and then the insulation sitting on top of that. There is
no surface on top of that; there's a big space up there."
C(A.S.) "But the insulation is one condensing surface."
C(D.Sa.) "Yes, but it's not like having a cold wall there with insulation,
so that the air passes through the insulation and then hits a cold surface."
C(T.B.) "The condensation happens right on the underside of the roof
sheathing. I've seen plenty of moisture damage in attics."
C(D.H.) "We agree with Terry and have published a number of reports on
attic (and crawlspace) moisture problems.
D(D.Sa.) "But at least attics are ventilated, whereas the wall is not
ventilated, so I think there's a bigger potential."
C(B.T.) "It might happen, but I think that [should be] a follow-up
measurement to this. We've been doing this only nine months, so we really
haven't been through it."
C( ) "Someone brought up an important point. If you could, with a smoke
pencil or other means, identify the large leakage paths existing in the
house, and plug the big holes, that might be of some value. As we know from
the moisture-damaged houses of the far north, the big problems happen when
there's a big leakage path. The other thing is that in the houses that
you've done, you're not going to see rot yet, because it takes a long time
to get to that. That's not to say that it won't happen."
Q(R.Si.) "I was wondering whether anyone had measured a bona fide change in
moisture before and after pressurization."
C(T.B.) "We've changed the whole humidity dynamic. A great deal of the
moisture in that building is probably entering with that soil gas. Now that
we've prevented that, we may have cut the moisture source strength by a
factor of two. We have countervaling physical principles going on here,
with no way of knowing whether we'll have a problem."
C( ) "We have measured relative humidity in upper floors and basements and
overpressures and we've seen declines almost universally in basement
humidity."
C(B.T.) "I have a few other comments, and the first one applies not only to
heat exchangers but also to basement pressurization. You have to decide
what overpressures you're going to operate at, and what are acceptable
overpressures, and what are the maximum flow rates that you can live with
when you actually set up your blower-door. Is 300 cfm too much, or 400 cfm?
For economics, we use something like 300 or 400 cfm as an upper bound. With
anything more than that you'll have a lot of drafts, and you also pay an
energy penalty to move this large volume of air. Another question concerns
the pressure: what pressure do you have to develop in the basement to
override 90% of the conditions. We're using something like 3 pascals
overpressure (difference between basement air and outside air) , but that may
not be enough, and that may be suitable only in certain climates. As you go
further north, you may have to go even higher, to override more extreme
conditions."
C(K.G.) "We have a couple diagnostic questions. Being from the energy
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field, we worry about home-owner comfort, and I think the location of the
fan intake is important. As Brad mentions, should we check for a local
drafty situation? Also, regarding the HVAC operation, most of our newer
homes have central air conditioning, so it would be a problem all year
round, not just during the heating season. Should we check the HVAC
operation and its effect on the pressurization system?"
C(T.B.) "That goes right along with my diagnostics question. What happens
to the pressure field when you turn on the furnace? And what happens if you
turn on the 'Jenaire' all of a sudden you're exhausting 400 or 500 cubic
feet per minute from the upstairs chamber in competition with the fan that's
blowing air down into the basement? The question is, how do we test for the
impact of other exhaust devices on our pressurization system? I suppose
that the answer is to turn them all on at once and see."
C(M.O.) "I'm sorry, but our time is up on this topic. Now we need to move
on to soil depressurization."
C(B.T.) "We talked about this a bit already yesterday. The most important
things to check are: how extensive a pressure field have you developed in
the soil? Is that strong enough to resist the competing pressures from
wintertime stack effect and from exhaust appliances? Also, do you have some
sort of 're-entrainment' That is, is the fan you're using somehow mining
high concentrations of soil gas and blowing it into the house, or is it
coming back in from from outside? Those are the three things you want to
test for, and I do that typically by using smoke sticks. If I were stranded
in an abandoned radon house, and could select only one thing to have with
me, it would be smoke sticks (not Bayer Asperin) and a respirator.
Magnehelics and incline manometers both have problems at the low end range.
You can tap Magnehelics and the needle will move and stay stuck in a
different spot. Incline manometers mean that everything you own has red
gauge oil on it. And they are slow to move if you're moving any air column,
you really have to wait for them to stabilize. Although they are expensive,
the electronic sensors maintain calibration very well, and respond
instantaneously. I think they are worth the money.
You can check with all those things. You can turn on all the exhaust
devices in the house, or artificially induce with a fan a wintertime-type
negative pressure, to see if you can overwhelm it the mitigation system,
and have soil gas entering where it used to be leaving, with your soil
depressurized."
C(D.S.) "if you have the design pressure in the weakest^part of your
system, then it is not going to be overcome by any wintertime design
conditions. For re-entrainment I check with the freon tracer. Two
important things to remember are that 1) silicone will give you a false
positive; it will beep like crazy at silicone, and 2) if freon comes into
contact with an open flame, phosgene is formed, which is not very nice
stuff."
Q(M.O) "Is there further diagnostic imput?"
A(D.Sa.) "I'd like to say something about radon mapping. We find that you
don't want to fix something which is not broken. If you have multiple
slabs, crawl spaces, holes, etc. you can go in there and make sniffer
measurements and decide where to mitigate and where not to mitigate."
C(I.N.) "We were talking about the dangers of tracer gasses. We should be
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glad that freon is not among those which react with ozone."
C(T.B.) "It depends on the one which you are using. Probably Rll and R12
will soon be banned. You can either use an R22, which is more acceptable,
... the ozone is a serious issue for me, and I don't lightly dump lots of
freon into the atmosphere."
C(L.K.) "Along the lines of what Terry was just saying about setting a
match to silicone, I think people should be cautious about the sealant they
use; make sure that it is appropriate for internal use. In my region the
Center for Disease Control is looking into a log cabin, where someone used
caulking on the inside of the house that was meant for external use only.
The caulking may have caused a child to be born with leukemia."
C(D.S.) "It has been stressed quality assurance and quality control is
important in the installation phase. It seems to me that many leaks could
be avoided by making sure that it's done right to begin with. It seems to
me that that should be one of the diagnostics in the installation. I'd like
to ask the mitigators how often they've had to go back and fix things that
weren't done right along those lines."
A(D.Sa.) "Do fifty percent of the systems have some sort of leaks?"
C( ) "I think that's too high -- maybe 25%".
C(M.Me) "Our standard procedure is to check out the system with freon when
it's installed. We do double-check sometimes; for instance, when we have an
installer putting in the system, the installer is supposed to check out the
system with freon before leaving the site, and we generally return within 48
or 72 hours and do an independent quality control check. We've found leaks
using freon in the air perhaps 10% of the time. These leaks occur in two
places: one is at the joint where the fan is coupled to the pipe going
outside, and the second one is at the band joists where the pipe is exiting
the house. That we find is frequently a difficult installation point,
because you're working with bends in the pipe in constricted space, often
between floor joists). It's the point where the utmost care has to be
taken"
C(A.S.) "I would comment that I really admire people who have the courage
to install fan systems with the portions internal that are under pressure.
I've never had enough courage for that and we've always mounted the fan
outside."
C(M.Me) "We're losing our courage.(laughter) The pictures we showed
yesterday had that roof-mounted fan for that reason. The problem is that in
terms of the installation costs, it's considerably more expensive, and so
we're generally offering people three alternatives: we say it's cheapest
and simplest to out through the side of the house, but here there are the
most serious concerns about venting. The second best is to go up through
the roof with the fan mounted in non-living space, an attic or crawl space.
Preferable is to get the fan ouside the house, mounted on the roof. Each
step buys you an additional level of protection, at an additional cost."
C(M.M.) "I'm not entirely sure whether ... although obviously it must be
smaller, we've seen no evidence in our installations where all our fans are
ground-mounted, that this prevents you from achieving 4 pCi/L per liter or
less, on average."
C(M.M.) "With ground-mounted [fans], our concern is with human traffic.
Most of our clients, in fact, have small children. That seems to be a
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driving force in installing mitigation systems in that 5 to 40 pCi/L range."
C(M.O.) "We have time for just a few more questions."
C(RSi) "I have a comment on the problems with the side mounts. We've found
a lot of re-entrainment six or eight feet away around the collar joists, or
band joists, or the plate foundation interface area. So, we've elected, if
at all possible, not to give the home-owner an option. We price the job
going through the roof system."
C(A.C.) "The new manual will show that as the only option."
C(R.Si) "Also, as was mentioned earlier, the problem going along with that
is inadvertant exposure of kids, even if there are plants or if the area is
protected. That's not a long-term protection mechanism. The [plants] could
be removed, and the area could then be used as a play area."
C(D.S.) "Just one more point, along the lines of the this quality
assurance, quality control. Someone mentioned double-checking: that should
be routine. And there should be a checklist. A lot of this seems to depend
on the experts: 'well, I know what should be done'. But there's no record
of what was done, and there should be a checklist as a diagnostic that
should be followed."
C(T.B.) "Actually, Bill Brodhead made a checklist for the ORP course for
each of these mitigation techniques. There's at least something written
down on paper."
C(D.S.) "A course is one thing, and practice is something else."
Q(T.B.) "Bill, do you actually use your checklist?" (laughter)
Q(L.H.) "I have another quick question for the mitigators. Are subslab
ventilation and dampers installed routinely in the system to balance the
flow during the installation?"
A(R.Si) "It's routine for us. We install damper systems to balance the
depressurized area, depending on what we're dealing with. It could depend
on whether it's going into an adjoining slab, or an area that doesn't have
the same type of pourous fill as another area, or possibly the specific area
that it's dealing with, so that we can adjust and have relatively uniform
flow throughout the system."
Q(L.H.) "Do you do that on the day of installation?"
C(M.O.) "Right."
C(M.O.) "Do you have a rule of thumb on dampers, as far as how many you
would have in a system?"
C(R.Si) "No, it's pretty specific as to what we're dealing with at the
time. We install dampers in every lateral."
C(M.O.) "OK, that's what I was [asking about]."
C(R.Si.) "The other thing is that if it's a direct line down from a fan, in
my experience, we'd have more direct draw from the straightest run of pipe,
and we want to be able to divert that through areas."
C(M.O.) "Our time is up, that ends the Phase III Diagnostics Section."
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PHASE IV. WORKSHOP DISCUSSIONS
POST MITIGATION DIAGNOSTICS - Bruce Henschel, Chairman
C(B.H.) Four basic diagnostic issues will be discussed here. First, what
is the universe of diagnostic techniques that might be considered under
post-mitigation diagnostics? Second, is each technique practical and cost
effective for a commercial mitigator to use? Third, our emphasis will cover
the confidence we have in the technique, the experience to date, the
improvements needed, and the interpretation of the results. Fourth, who
should use the technique? The commercial mitigator, the homeowner (long
term items), or the research community? What kind of diagnostics should be
used if the system is working, but not achieving the 4 pCi/L guideline value
is an interesting question but should be referred back to the earlier
diagnostic categories.
"In order to conserve our discussion time I will start the informal talk
on the list of diagnostic techniques for post mitigation. What are the
universe of techniques that fall into this category of diagnostics? The
obvious techniques include measurement of Rn and/or Rn progeny. Should we
measure Rn gas or Rn progeny or both? Where should we make the measurements
--in the living space, or the basement; or from a research standpoint, in
walls or under the slab? What is the timing and duration of these
measurements (i.e., short term, long term measurements)? What levels are we
looking for -- does every measurement have to be less than 4 pCi/L?
"Another diagnostic technique is evaluating the effect of weather and
events such as appliance use on the radon inflow.
"A third diagnostic item is evaluation of mitigation system fan size.
"A fourth item is the evaluation of back drafting of combustion
appliances with the mitigation system operating and depressurizing part of
the house.
"A fifth diagnostic item is visual inspection, seal functioning over
time. Moisture problems such as band joist rot due to moisture extracted by
the mitigation system, etc. and a sixth, the effect of SSV on the soil
around the foundation -- possible freezing problems, drying out the soil,
etc.
"Finally, as a general category, other side effects such as ill effects
from the caulking, etc."
Q(D.S.) "This list has many items the commercial sector may not be
interested in. Who has the long term responsibility for the system
operation and side effects?"
A(B.H.) "I am assuming that the homeowner may have to take the
responsibility for the long term items. In addition, researchers may have
similar interests for the long term. The techniques listed that should have
the most interest to commercial mitigators are measurements of radon and
radon progeny, and assessment of weather, appliances, and back drafting.
Their interest in optimal fan sizing may prove to be a question mark."
Q(A.C.) "What part of the post-mitigation diagnostics is the commercial
mitigators responsibility, and what part is somebody elses? David Saum,
what do you guarantee as far as reduction of radon below a certain level?"
A(D.Sa.) " My guarantee is for a year, nominally. Long term testing is an
interesting area, but we have had trouble finding a group who routinely
handles the long term. We provide charcoal cannisters and alpha track
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measurement devices for the intermediate term."
C(A.C.) "Part of the EPA demonstration program will be to continue yearly
testing for at least five years on all of the houses that were mitigated in
the studies. We will perform a three-month alpha track survey during the
winter season. In the New York study we are going back to resurvey what
they did four years ago to see how well the mitigation has held up and to
determine if there are any problems."
C(T.B.) "When it comes to problems, the homeowners determine who they will
turn to for assistance. Sunday morning calls are a real problem for the
mitigator."
A(A.C.) "In most states the mitigator doesn't have any responsibility
beyond one year."
C(T.B.) "Unfortunately most homeowners do not believe that. I have calls
on houses I built five years ago, but now the homeowner has installed a
dimmer switch that bothers his radio and its my fault. The homeowner will
hold the person that did the work responsible as long as possible."
A(M.Me.) "Let me quickly explain which tests we do and why. Once our
system has gone through our quality control check, we supply the homeowner
with charcoal canisters which they place in the house for checking
performance over the intermediate term. Once we get back an indication that
radon levels are below 4 pCi/L, then we install alpha track for a three-
month evaluation. Since we are often heading into spring-summer, we ask the
homeowner to wait until the next winter to make this three-month test. We
have discussed radon progeny measurements but since we don't have the before
measurement of radon progeny, an extensive set of after measurements creates
a new set of problems for ourselves. The before diagnostics limit what post
diagnostics are appropriate. The post set of measurements are limited to
radon, not pressures, etc. We are 'listening for side effects', but that is
the extent of it."
C( ) "In the case of 12 mitigation companies in New Jersey, the testing is
far more limited than that described here. Very few are doing much in the
the way of diagnostics. It is very simple out there, let's get in, put
something in place, let the homeowner see what the results are. No one is
doing work adjusting dampers, two are doing freon post-tests. There isn't a
lot of diagnostics going on out there."
C(T.B.) "Chick and I surveyed a number of installations in New Jersey.
About half the systems weren't working properly but could have been if
simple post-mitigation diagnostics had been used, such as checking the
effect of the 'suction away from the suction hole."
C( ) "Even the simple post-mitigation measurement of radon concentration
has been left up to the homeowner. One example of really simple diagnostics
used by a company who has installed 400 SSV systems is to put two five-
gallon buckets of water down the 4-inch diameter suction hole. If it moves
quickly into the soil this means good communication and they proceed. If
the water isn't quickly drained they move out to the edge near the footer
and drill additional suction holes counting on the soil to have fallen away
from the footer and thus providing good perimeter communication. They might
also move to trenching. What ever is done on radon or radon progeny is the
responsibility of the homeowner."
C(R.Si) "Check lists are important for each specific system."
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C(R.S.) "A competent diagnostician should be checking that the whole house
works successfully, e.g., interaction between the mitigation systems and
appliances, etc. There is a moral responsibility for following up the
higher radon houses, say greater than 50 pCi/L. Both the research community
and government officials must make the commitment to provide the kind of
understanding necessary through a long-term radon measurement program to
evaluate these mechanical mitigation systems over the long term."
C(T.T.) "I like radon measurements for post-mitigation diagnostics. If you
kill the parent you don't have to put up with the children. We don't need
to measure working levels; we have never accounted for the unattached
fraction of daughter products. I use a grab sample profile of radon and
compare it to the pre-mitigation data. I have had 100% success in
predicting whether the home will exceed the annual radon average based on
radon data (employed on 80% of a 600 home sample, involved with mine
tailings). I also look for hot spots in the radon profile survey."
Q(D.S.) "Are you looking at an annual performance? That is where the 4
pCi/L came from?"
A.(T.T.) "I am comparing to a year-long Ripsu sampling."
C(D.S.) "We are talking about annual average and not a grab sample and then
you are done. "
C(T.T.) "I thought we were talking about several phases of post mitigation.
I am suggesting a method to let you know where you are."
C(R.S.) "A grab sample isn't the whole story. One must consider longer
term measurements such as alpha trak in several locations as a minimum."
C(M.C.) "New Jersey has requested each mitigator to supply before-ahd-
after measurements to show what has been achieved. These are mostly carbon
canister measurements of radon and not longer-term measurements."
C(T.B.) "We have a serious problem in the private sector with conflict of
interest. If I were doing commercial mitigation work I would make sure the
pre-mitigation reading was high and all post-mitigation reading would be
low. The potential for fraud is extremely high after selling thousands of
dollars of mitigation. We need independent radon testing because there is
the whole question of liability if you take your own measurements."
Q(T.T.) "What is an annual average? What does it mean when we obtain it?
Is it reproducible the next year?"
A( ) "No, there is no such thing as an annual average is the answer."
Q(I.N.) "Since there are a number of EPA people here, in subsequent
revisions of protocols is EPA going to reconcile .02WL and 4 pCi/L? EPA
should resolve the question. In some areas it pays to measure radon progeny
because of the equilibrium fraction is less than 50%. EPA should settle on
either radon or radon progeny. These questions are becoming central to real
estate transactions."
A( ) "The guideline is written in terms of 4 pCi/L for indoor radon, the
type we are discussing."
A(A.C.) "No, in every case it's given both ways."
A(W.L.) "The conception in the research community considers the ultimate
dose to the lungs and risk. Because of compensating factors the dose models
indicate that radon gas measurement is probably better as an approximation
to dose than radon progeny in contrast to what we thought a few years ago.
In a sense there is a very strong movement toward radon measurement and
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guides because of its practicality but also because it makes more sense from
ultimate risk."
A(A.C.) "From the EPA demonstration programs, the decision making is based
on radon, continuous monitoring or canisters."
C(B.H.) "The measurement of radon and ventilation effects is a critical
area for continued research. What happens to WL and unattached fraction are
closely related to ventilation taking place in the space."
Q( ) "Don't we know what is the unattached fraction? The health community
is saying probably the unattached fraction makes up for the difference in
ratio and consequently either one gives you essentially the same thing.
What happens to the unattached fraction depends on the system --is there a
filter present -- these points need to be looked into."
C(R.S.) "We can't rely on WL measurements to have any assurance that you
have made any improvement in the radon situation."
Q(A.C.) "Are any real estate companies requiring WL measurement?"
A( ) "Yes, in Pennsylvania. A real estate relocation company is using WL
measurements with continuous monitoring over one day. This is one of the
two largest relocation real estate firms in the country. Home Equity
Relocation."
Q( ) "What instrument are they using?"
C( ) "That depends on the contractor, they don't do their own testing."
(Some discussion on the size of the real estate market handled by such
firms.)
C(B.H.) "Summarizing, radon is easier to measure and may be a better
indicator given that you have to make a fairly simple measurement -- you
can't be measuring WL as a function of particle size in every house the
commercial mitigator goes into."
Q(T.B.) "I have almost given up on summertime measurements because of the
seasonal variability. Who is going to do long term monitoring in buildings?
I don't think it is the mitigator's job."
Q( ) "That is an important issue and gets back to the question of isn't it
the homeowner's responsibility to measure his house over the longer term?"
A(T.B) "The mitigator leaving canisters for follow up measurements was one
idea advanced. A commercial house offering that service is also very
interesting. New Jersey's follow up program is another example of longer
term testing."
A(A.C.) "Your getting back to the question of "is it a legal
responsibility? EPA's program is a voluntary program and always will be
because we don't have the legislative mandate to set a regulation. Some
states are setting regulations. There will not, as far as we know, ever be
a Federal regulation."
C(J.H.) "New Jersey has done 1400 confirmatory tests and 200 post remedial
tests. One major problem is that the homeowner doesn't want the government
to know the level of radon in their house. They don't trust the government
unless they need some financial support. Interesting findings from the post
remedial tests; about 47% used sealing, 18% used HRVs, 22% used SSV, the
rest used other ventilation systems or methods. Thirty-nine percent did the
remediation themselves even though the homeowners were well-off financially.
These owners are concerned with cost. Before mitigation 97% were above 4
pCi/L, while after mitigation 48% were above 4 pCi/L."
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C(A.C.) "About half made it to the guideline."
C(J.H.) "The before levels were between 3 and 400 pCi/L."
C(A.C.) "The goal of the mitigator in any home is not for a given percent
reduction, but is to get the post-reading as low as possible, and at least
below 4 pCi/L."
Q(D.S.) "Cost effectiveness was cited as one of the issues. You must put
mitigation on an objective basis. We really haven't done that in the U.S.
Sweden is doing that. Are there any ideas at this point of how to pursue
that goal?"
C(A.T.) "In some places dehydration will occur to depths of several meters.
It could significantly increase radon transport."
Q(B.T) "Why wouldn't it decrease the source strength because of emination
fraction?"
A(A.T.) "You are talking about moisture changes of a few percent while I am
talking about changes from 60% to 30%."
C(T.B.) "You get condensation on top of the SSV pipe. If you've done the
installation correctly the moisture runs back into the soil, otherwise it
interferes with the fan and you'll hve to fix it."
C(A.T.) "I don't know if it is a real effect, all I know is if it does
dehydrate the sail it will have an influence on the source term."
C(A.C.) "Larry Kaplan reported that in one installation he was monitoring
the SSV system produced 2 1/2 gallons of condensate per day."
Q(T.B.) "Was it running back into the soil?"
A(A.C.) "He was draining it away, but I don't know exactly how he was doing
it."
C(B.H.) "In terms of the diagnostics we would use to evaluate this, it
might be in the realm of the developers and the researchers either measuring
changes in the source term, or the moisture content of the soil or something
to that effect over the course of the project."
C(A.T.) "If you're doing periodic monitoring over years, and finding the
radon levels are rising and the mechanical mitigation system is working,
this could be the reason for the source terms changes.
C( ) "I think the opposite situation takes place. As the soil drys out
the suction system becomes more effective and reaches out further and the
performance gets better."
C(A.T.) "I claim some knowledge only of the source term."
C(A.C.) "As long as you have a negative pressure difference across floor
and wall cracks it probably doesn't really matter how dry you get the soil.
Even if the source strength increases it doesn't mean more radon will enter
"the house. "
C(A.T.) "That's a good pointp; the key is that the gradient is toward the
soil."
Q(B.H.) "Our time is running out and I would like to turn the discussion
back to radon monitoring, something near and dear to everyone. The question
is where do we monitor? For those that are doing monitoring as part of
commercial installations where do you monitor - upstairs, basement, both
places?"
A(T.T.) "Usually we monitor 6 to 8 places in the house. I think many
people are overlooking that radon levels can increase in living spaces while
being reduced in the lower house locations. I believe a profile of radon
122
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Radon Diagnostics Workshop, 1987. Phase IV
levels is necessary, not just basement measurements."
A(D.Sa.) "We try to make radon measurements in a couple of places that were
measured before, often on each floor."
A(M.Me.) "Always a minimum of two charcoal canisters are used, plus one
alpha track which the homeowner decides on the placement."
A(I.N.) "We try to follow the EPA protocalls."
Q( ) "Oh my God, I'm sorry for you."
Q( ) "Which one?"
C(I.N;) "It is rather difficult. There are two types of measurements the
EPA suggests. One is the screening measurement which is done at the lowest
level of the house. The other is the so-called follow up measurements which
in the present protocol is the pre-mitigation follow up. So you would try
to duplicate those location measurements in the post-mitigation measurements
with the charcoal canisters. The measurement of radon or radon progeny is
still a question."
C( ) "One of the problems that drives the pre- and post-mitigation
measurements is the time delay that is necessary to purge the lucas cell
after measuring a hot spot. There is a definite research need to develop a
rapid radon measurement system which doesn't have the problem measuring the
radon daughters. That development would change the whole complextion of
what pre- and post-mitigation measurements would be made."
C(A.S.) "Eberline appearently has been working on an electrostatic cell
that removes the daughters and measures radon."
C(A.T.) "Paul Tease claims a patent on that."
C(D.Sa) "Sniffing measurements limited to only a few minutes has allowed us
to quickly clear the cell even when covering ranges from 10 to a 1000 pCi/L.
v We also seem to see significant reductions under the slab. You don't
' agree?"
C( ) "The holes drilled into slab and walls for diagnostics have been
plugged with putty or tape until after the system is installed. The
principal.measurements have been pressure but where we have interesting
houses we have gone back, time permitting, and we sniff there on how quickly
radon levels drop and how far.
Q(A.C.) "What is the highest levels you've measured after several months?"
A(A.S.) "50,000 pCi/L near the beginning of monitoring in the spring, and
35,000 the following fall out of the subslab."
C(A.C.) "We have seen some very high levels even after long periods of
time."
C(B.W.) "I would like to tell the story of a building contractor in
Pennsylvania who filled out a form to his insurance company that he was now
going to install radon mitigation systems. The next day he received notice
his insurance was cancelled. We are in the business of installing
ventilation systems is the response to that issue."
C(W.L.) "I want to go back to the issue of long term effectiveness of
mitigation. It is clear there is not going to be federal regulation on this
issue in the near future. States are taking some actions; some will take
different actions and that may not be a very satisfactory situation. That
raises the question of whether the industry could develop a voluntary
standard, especially the cream of the crop which is here."
A(B.T.) "The ASTM task group is attempting to look at a standard for long
123
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Radon Diagnostics Workshop, 1987. Phase IV
term measurements.
C(A.C.) "They will never get 50% of the mitigators to belong."
C( ) "But that's better than 10%."
C( ) "But it's possible that the EPA could come out with a recommendation
that the states could put into their regulations for long term
measurements."
C(D.S.) "EPA began to get involved with ASTM 1 1/2 years ago in that same
subcommittee. I haven't heard of any change in that policy to work through
ASTM to set up such guidelines."
C(A.C.) "Eighty percent of the mitigators have never heard of ASTM."
C(D.Sa.) "If we had the guideline in hand, it might take three years to
move to approval. The process is very slow."
C( ) "A group of leading mitigators is one idea that has been discussed as
a voluntary type of control. Dissemenation and gathering of information as
well as a form of regulating body that would overse the type of mitigation
installations and establish minimum standards. We are looking for
volunteers."
C(T.M.) "Such an organization would help to upgrade the image of this new
industry as well as raise the prestige of mitigators who subscribe to the
guidelines."
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SUPPLEMENTAL RADON DIAGNOSTICS INFORMATION
FROM THE PIEDMONT STUDY
Lynn M. Hubbard, Tony M. Lovell, David L. Bohac, Craig A. Decker
Kenneth G. Gadsby, David T. Harrje, Robert H. Socolow
Center for Energy and Environmental Studies
Princeton University
The Piedmont Study refers to the detailed radon mitigation and
diagnostic study conducted in 14 homes in the New Jersey Piedmont area from
9/86 to 9/87. Seven homes were investigated by Lawrence Berkeley Laboratory
and a second set of seven homes were studied by Oak Ridge National Labs and
Princeton University. This data-intensive, instrumented study was
cooperatively funded by the U.S. Environmental Protection Agency, the U.S.
Department of Energy, and the New Jersey Department of Environmental
Protection.
Instrumented measurements included: (1) basement and upstairs radon;
(2) differential pressures across the basement/subslab, basement/upstairs
and basement/outdoor interfaces; (3) temperatures at basement, upstairs and
outdoor locations; and (4) central air handler usage. A weather station was
located at house i?5, monitoring: (1) wind speed and direction, (2)
barometric pressure, (3) precipitation, (4) soil temperature, and (5)
outdoor temperature and relative humidity. A time-averaged value of all of
the above parameters was recorded every 30 min. Several additional
parameters were monitored on an intermittent basis in all or selected homes.
These included multizone air infiltration rates which have been measured in
all homes using passive perfluorocarbon tracers (PFT), and in one home using
a constant concentration tracer gas system (CCTG).
The purpose of the analysis of the continuous time series data set
available from the Piedmont Study is to provide insight into both the
usefulness and accuracy of some of the diagnostic measurements made by
practitioners as well as insight on the interaction of various measured
parameters with the time-varying radon concentration. The analysis
presented here was performed at Princeton University using the data from the
seven Princeton/ORNL research homes. These homes were chosen to be of
similar basement types, and Table 1 compares substructure specifics and
other house parameters.
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Table 1. Summary of house parameters.
House
No.
Sub-Structure
Modifiers
HVAC
foCl/L)
ACH
(h'1)0- Soil
-50 Pa. Perm.
I Basement W/Slab, Float. Slab,
Att. Gar. W/Slab Sump
II Basement, Sump
Att. Gar. W/Slab
III- Basement, Float. Slab,
Att. Gar. W./Slab Sump
IV Basement W/Slab, 2 Sumps
Att. Gar. W/Slab
Cent. F.A.
Gas
Cent. F.A.
Gas, W/AC
Cent. F.A.
Oil
Cent. F.A.,
Oil W/AC,
Auto Setback
B:73
U:16
B:24
U:16
A:15
B:156
U:49
A:60
B:103
B:128
U:31
16.2
12.3
11.9
9.9
Mod.
Mod.
Mod.
Very
V Basement, Float. Slab,
Att. Gar. W/Slab
Cent. F.A.,
B:60
Elec. Ht Pump, U:25
Auto Setback U:36
8.2
High
VI Basement W/Crawl 2 Ht Exc.
Att. Gar. W/Slab Sump
VII Basement W/Crawl Float. Slab,
Att. Gar. W/Slab Sump
(Part. Seal)
Cent. F.A., W Ht Exc 19.8
Oil, W/AC, B:25, U:14
Auto Setback W/0 Ht Exc
B:30-35
Cent. F.A.,
Gas, W/AC,
B:36
11.0
High
Very
Low
a control house
b B - basement or crawlspace, U - 1st floor above grade,
A - 2nd floor above grade
c. depressurization only, basement door closed, blower door on main
entrance, Nov., 1986 measurements.
126
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One question which is often asked by both researchers and practitioners
regards the difference in accuracy in a two day versus a four day
measurement of the average radon concentration. How much better is a four
day average over a two day average? Without addressing the question of the
accuracy of the measurement device itself, we have used the Piedmont data on
continuous radon measurements to determine how variable the two day versus
four day averages are over different seasons.
Figure 1 plots the differences between nested two day and four day
averages for the control house over 200 days of the study. Each point is
the difference between the average radon level over a two day period and the
average over the four days centered about the two day span. The average
difference is zero if a long enough time span is considered, but any given
difference can be either positive or negative, with an alternation in sign
being the norm. The standard deviations noted on the figure are those
associated with the DIFFERENCES, not the radon levels over the period. For
the winter, the deviation of 1.40 pCi/L is 6.4% of the radon level. This
represents the scatter attributable to your choice of two versus four day
sample intervals.
Figure 2 is the scatter plot of the two day averages versus the
associated four day averages. The differences between the averages account
for the deviation of the points from the straight line. The standard
deviations given are those of the daily radon levels over each season.
Different symbols are used for each season to show how the radon levels
changed over the long term.
Figure 3 shows a four day span of basement radon levels in two homes
during a period of no rainfall. Although one of the radon curves has a very
dynamic character and the other is somewhat static, the differences between
the 2 and 4 day averages for BOTH curves is negligible.
Figure 4 shows a basement radon level reacting strongly to rainfall.
The spike produced by rainfall dominates the curve, and the choice of either
a 2, 3 or 4 day sample interval makes about a 10% difference in the actual
average radon level for this house during one rainstorm. This 10% figure is
comparable or less then the statistical variations commonly found in the
readings of passive sampling devices placed side by side, however it could
become significant as the error in the passive sampling devices improves.
The behavior of House 7 during rainfall, displayed in Figure 4, had the
largest response to rain out of the seven Princeton/ORNL homes.
The top box in Figure 5 shows the variation in the basement and
upstairs daily radon concentration during one week in February. The Julian
date is shown at the bottom. The basement radon concentration has a
distinct diurnal periodicity with the daily minimum varying from the maximum
by a factor of between 1.5 and 2. Use of the heating system appears to be
part of this diurnal cycle. The heating system consists of an oil
combustion unit with a heat pump, located in the basement, with a forced air
distribution system throughout the house. During the sleeping hours the
system is manually shut off, and the basement radon slowly builds up. When
the homeowner rises between 7 and 8 a.m. the oil combustion unit is manually
127
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turned on and left on until the upstairs temperature reaches approximately
70 F. The system is then manually switched over to the heat pump, which
continues running automatically on a thermostat throughout the day. If the
outside temperature drops below 30 F during that time, the system
automatically switches over to the oil burner again. Before retiring at
night, the homeowner again manually turns off the entire heating system.
The second box in Figure 5 shows the basement infiltration (in air changes
per hour, ACH) averaged over hourly time periods using the constant
concentration tracer gas system (CCTG). The third box plots the difference
between the upstairs minus the outdoors temperature (top curve), and the
percent time in each 30 minute time period that air is flowing through the
air handler (bottom curve, with units given on the right ordinate). This
measurement does not distinguish between oil combustion and heat pump use.
The bottom graph plots the outdoor minus basement and subslab minus basement
pressure differences in Pascals. The more positive this difference is, the
greater the depressurization of the basement relative to the subslab or
outdoors.
These graphs tell the following story. The basement radon builds up
during the night, when there is no heater operation. Once the heater comes
on the basement air gets mixed with the upstairs air, and a slight buildup
in the upstairs radon concentration can be seen to occur during the period
when the basement radon is decreasing (top graph). The basement is
depressurized relative to the outdoors, subslab, (bottom graph) and upstairs
(not shown) during the cold winter days plotted here. Deviations from this
baseline occur in the initial combustion stage of the heater use. (Note:
the overall increased outdoor - basement pressure difference over the period
between days 54.5 to 56.0 corresponds to a strong and steady wind from the
northwest. This correlated behavior also shows up in other time periods.)
Three processes can occur during heater use which affect the basement
radon concentration. 1) The basement air becomes mixed with the upstairs
air, which dilutes the radon. 2) The increased depressurization of the
basement can increase the amount of soil gas, and thus radon, flowing into
the basement, increasing the indoor radon concentration. 3) The increased
depressurization of the basement can increase the amount of outdoor air
flowing into the basement, diluting the indoor radon concentration. The
difference in the leakiness between the substructure and soil gas compared
to that of the substructure and the outdoors determines whether process 2 or
3 above will dominate, and thus whether the basement radon concentration
will be enhanced or diminished. Along with the increased basement
depressurization during the initial combustion stage of heater use, the
second graph shows an increase in the basement infiltration of about a
factor of 1.5 to 2.0. The basement infiltration is the sum of the
infiltration from the outdoors plus the infiltration from the soil gas.
There is a way to make the second of these terms go to zero, and thus obtain
the relative magnitudes of each of these two terms in the unperturbed case.
The perturbation which can be applied is a subslab ventilation system.
With a subslab ventilation (SSV) system operating and effectively
reducing the indoor radon levels to below 4 pCi/L, the basement infiltration
from the soil gas is negligible. The total basement infiltration would then
128
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consist only of the contribution from the outdoors to the basement. It is
possible that the SSV system can cause increased air to flow from the
basement either out through porous hollow block walls or by some other
mechanism out of the basement into the subslab and out the SSV system.
Consequently, this could increase the basement infiltration from the
outdoors. Comparing the basement infiltration with and without SSV in use
will still give information on the difference between the infiltration from
the soil gas versus the outdoor air, since any increase in outdoor to
basement infiltration due to the SSV operation would be more of a constant
source rather than sharp changes as observed when the combustion heater
comes on. Also, initial analysis does not show any significant shift in the
baseline for the basement infiltration when compared to conditions without
the SSV system operating.
Figure 6 is a plot of the same parameters as in Figure 5, for four days
when the SSV system was operating, subsequent to the days plotted in Figure
5. The radon concentrations dropped to well below 4 pCi/L, indicating the
SSV system was effective. (Any measurement of radon below 1 pCi/L is within
the error limits of the detector). The bottom graph shows that the subslab
air is depressurized relative to the basement air by about 13 Pa, due to
operation of the SSV system. The large increase in the basement
infiltration at day 59.6 is due to the homeowner airing the basement. The
average basement infiltration during the initial use of the oil combustion
system each day is 0.33 ACH for days 50-58 (Figure 5) and 0.28 for days 58-
62 (Figure 6). The difference between these numbers suggests approximately
0.05 ACH infiltrates the basement from the soil gas during the combustion
phase of heater use, when the SSV system is not operating. Although this
analysis is preliminary and trends are suggested, future more controlled
experiments are needed.
No significant change in the baseline for the basement infiltration is
observed in this preliminary analysis, any overall decrease due to stopping
infiltration from the soil gas may have been compensated by increased
infiltration from outdoor air due to any air flow from the basement during
SSV system operation. Leaving that for future more detailed analysis, the
data here suggest that in house 5 (the tightest house in the 7 study homes)
between 1/6 and 1/4 of the total infiltration into the basement is from the
soil gas when the SSV system is not in operation.
Figure 6a shows the radon concentration in the basement, in one
location of the inner hollow block wall, and in the subslab gas under the
center of the slab during February 20 through March 2 (Julian day 51-61, as
shown in Figures 5 and 6). It is interesting how much higher the wall
concentration is than the subslab concentration; which was consistent over
time in these two specific locations. We did not find any other wall
location in this house which gave readings this high. The wall faces east
and is not adjacent to a slab on grade. (Note that hollow block walls
between a basement and a slab are often the hottest wall in a given
structure, due to the slab trapping soil gas.) The wall radon shows some of
the daily periodicity displayed by the basement radon concentration and, to
a lesser extent, so does the subslab radon concentration. The wall has
better air flow communication than the subslab with the basement air due to
129
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the very porous nature of the cinder (or concrete) hollow block walls. This
points out the role of porous walls in soil gas entry.
The perimeter drain seal shown in the insert in Figure 6a is an
effective way to close perimeter drains, while still allowing the SSV system
to communicate with the air in the hollow walls. This is demonstrated on
February 26^ when the SSV system is turned on and all the radon
concentrations drastically drop. In particular it is interesting how the
wall radon level actually drops lower then the subslab level implying more
effective ventilation of the walls than the center of the subslab area. The
two SSV penetrations into the subslab in this house were located opposite
and adjacent to the wall where the radon concentration was measured, and
about equidistant from both subslab and wall radon monitoring locations.
Another way to look at the data is to average the different parameters
over time periods that the time-integrating perfluorocarbon tracer gases
were deployed in each house (Figures 7-9) . The perfluorocarbon tracer (PFT)
gas system measures average air flow rates in multizone buildings. This
technique measures both infiltration and interzone air flow rates using
passive sources and samplers.
Each of the seven research houses has been monitored with PFT systems
since the instrumentation packages were installed at the end of October,
1986. The PFT measurements have been made over typically two week periods
uninterrupted (except for short time periods during mitigation installation)
from the time of installation until late spring to mid-summer, 1986.
Figures 7 and 9 extend through May 15th and Figure 8 extends to July 29th.
The final calibrations for the PFT technique have been applied to the
computation of the air flow rates for these houses.
The method for looking at the PFT data with the other parameters
consists of averaging the continuously logged parameters over each time
period that the PFT's were active in each house, (which varied slightly
between each house). Figures 7-9 show this averaged data for homes 1, 5,
and 2 (the control house), taking into account the specific PFT time periods
for each home. The top box in each figure plots the radon concentrations in
the basement and upstairs. The second box displays the basement air
infiltration rate (solid line) and the radon source strength (broken line).
The third box shows the three logged temperatures at each house: basement,
upstairs and outside. The fourth box plots the differential pressures
between the basement and the outdoors, subslab, and upstairs (as in Figures
5 and 6) . The points on each line represent the average of that parameter
using the given PFT time period. The lines across the top of the upper box
on each of figures show each PFT time period, which is specific for each
house. Shown on the abscissa of the lowest box are the Julian dates.
The seasonal trends are evident, with the outdoor minimum temperature
occurring in late January, lowered humidity in the winter, and increased
HVAC usage in the winter (the last two parameters are not shown in these
graphs). The installation of the mitigation systems in all but the control
house (#2) is evident by the decreased levels of radon and larger basement -
subslab pressure differences.
130
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The radon source strength displayed in the second box is obtained by
assuming the radon behaves similarly to the PFT tracer gas. The
relationship between the average emission rate (or source strength) of the
tracer gas and the average tracer gas concentration is given by:
Source (PFT in basement) - Average Concentration (PFT in basement) * K,
where K - a function of all of the air flows in the building. In the PFT
experiments, the source term is known and the average concentration is
measured. The value of K can then be computed and used in the same
equation, with radon source and average concentration replacing the PFT
terms. Knowing the average concentration of radon in the basement from
averaging the Wrenn chamber data, i.e., the top box on the figure, the radon
source strength can then be estimated.
Figure 9 displays the radon source rate into the basement for House #2,
(the control house, which was not be mitigated until July, 1987) which shows
a seasonal trend with a strong winter peak. However, since both the radon
source rate and basement infiltration rate (the major determinant of K)
increase during the winter, the radon concentration does not have a large
winter peak. In fact, there is not a strong seasonal component in the radon
concentration at all. House #1 (Figure 7) shows behavior similar to House
#2 (Figure 9) for the basement air infiltration rate. Instead of a seasonal
dependance, the radon source strength for House #1 decreases and remains low
after mitigation. This indicates that the reduced radon levels in the
basement are due to decreased source rates brought about by mitigation and
not due to increased infiltration levels.
Figures 7 and 8 display some interesting behavior. Houses 1 and 5 are
both ranch style homes of about the same size, and their initial, pre-
mitigation radon concentrations were similar. The basement infiltration in
house 1 is much larger than that in house 5, however, and along with the
increased infiltration in house 1 is a larger radon source strength. Recall
the above discussion about the two terms which make up the total basement
infiltration, i.e., the infiltration from the soil gas and the infiltration
from the outdoor air. During SSV operation the infiltration from the soil
gas should go to zero. The time point when the SSV system becomes operable
coincides with the basement - subslab pressure difference becoming negative.
The radon source strengths (and radon concentrations) drop dramatically in
both houses during SSV operation. The basement infiltration in house 1
remains high, while in house 5 it is significantly reduced during SSV
operation. This implies that the fraction of air infiltrating the basement
from the soil gas is much less of the total basement infiltration in house 1
compared to house 5. It could be possible that the total flow of soil gas
infiltrating each basement is similar, but that in the leaky house 1 this
flow is a much smaller percentage of the total basement infiltration. If
this were the case, the radon concentration in the soil gas would have to be
higher in house 1 to give similar initial basement radon concentrations.
We know from the Piedmont data, and other studies, that radon
concentrations can vary diurnally by as much as a factor of two due to
131
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environmental effects. Homeowner interaction with the house can increase
this variation much more due to window and door openings and closings. This
variation causes a large uncertainty in the use of grab samples to determine
radon concentrations. To better quantify the magnitude of this uncertainty
the 24-hour average of both the basement and upstairs radon concentrations
has been calculated in the seven Princeton/ORNL research homes. Figures 10-
15 show these 24-hour averages during the pre-mitigation time period of
October through December, 1986. All of the data points from each half hour
during this three month period are averaged and plotted as 48 points in the
24 hour day. The line inside each box is the median of the data, and the
box contains the inner 50% of the data. The lines which extend out from
each side of the box extend to the extremes of the data or 1.5 times the
distance from the median line to the edge of the box. The starred values
are the outliers, points that lie beyond the above definition.
Figure 10 displays the averaged 24 hour basement radon concentration
for the very periodic house 5 discussed above. Figure 11 shows the heater
use and Figure 12 shows the upstairs radon concentration. The coupling
between these 3 parameters is obvious (as discussed above). When the heater
comes on the basement radon is reduced and the upstairs radon increases by
about 10 pCi/L, on the average. Figures 13 through 15 are similar graphs
for house 3 in the study. Neither house 3, nor any of the other homes in
the study showed the same periodicity as house 5, although some of the other
homes displayed a somewhat periodic nature in one or more of the other
parameters (see Figure 15 for house 3 HVAC use) . One of the more striking
aspects of the plots for house 3 and the other 5 homes shown is the constant
nature of the median and inner 50% of the data on radon concentrations over
the 24 hour period. For high indoor radon concentrations, a grab sample
will give a reasonable indication of the magnitude of the indoor radon
concentration (as long as the homeowner has not been airing the house) . For
low indoor radon concentrations, grab sampling is not a useful diagnostic
tool because of the associated error.
132
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House 2 Radon Averages
(2 day) - (4 day) Averages
o>
w
<»>
'C
D
O
o
O
OL
Julian Date
450
500
PIT/CEF.S RN87
-------
40
30-
co
-------
90
Basement Radon Levels
No Rainfall
G60
a.
JS
c
o
gao
QL
Days in Average
353 - 357
353 - 356
353 - 355
Avg Rn H5
65 pCi/1
65
64
House 5
House 6
353
354
Figure 3
355
Julian Date
356
357
FU/CF.KS RNR7
-------
Basement Radon Levels
House 7, Rainfall Period
Day9 in Avaraga
324 - 328
324 - 327
324 - 326
Avg Rn Laval
33 pCl/L
324
325
Figure 4
326
Julian Date
327
326
-------
Houaa 5
70
60
50
. 30
20
10
0
.8
.7
~ .6
I .5
t .4
I-*
* -3
i 2
(D £
.1
0
30
25
\ 20
u 15
6
5
4
3
2
1
0
Basement Rn
- Upstairs Rn
300
250
200 3
150 |
100 |
^
50
0
50
51
52
53 54 55 56
Julian Date
57
58
Bsmnt-Outdoar
Figure 5
- Bsmnt-Subslab
137
PU/CEES RN87
-------
House 5
u
a.
8
7
6
5
4
3
2
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PART D
RADON DIAGNOSTICS MASTER LIST
The following is a list of diagnostic techniques that have been used
for determining the existence and extent of a radon problem. What type of
information and to what extent each of these techniques have been useful
will not be discussed here.
Phase 1. Initial Problem Assessment Diagnostics.
The following diagnostic techniques can be used for characterizing
either existing structures and their sites, or new construction sites.
a. Mobile radiological van for radiation scans both outdoors
and indoors.
b. Mapping of soil gas radon concentrations.
c. Mapping of soil permeability.
The following diagnostic techniques can be used for characterizing
existing structures.
a. Visual inspection of structure with completion of questionnaire on
building and house occupancy characteristics.
b. Determine radon concentrations in one or many zones within the
structure. Many techniques are available for doing this such as grab
samples, carbon cannisters or alpha track for integrated samples, continuous
monitors, working level monitors.
Phase 2. Pre-mitigation Diagnostics.
a. Natural condition grab sample in each zone and in holes drilled
into the subslab, into the hollow block walls if they exist, or through any
other existing membrane suspected as a radon source.
b. Repeat a. under mechanical -10 Pa depressurization using a blower
door.
c. Blower door test of the whole house or parts of house where
possible or interesting, to evaluate building envelope tightness.
d. IR scan of each room, to evaluate building envelope tightness.
e. Basement/subslab and basement/wall communications using single or
variable speed motor to pressurize or depressurize the subslab area. Check
pressure differentials between the basement and subslab on walls through the
test holes and check air velocity through the test holes to determine
communication from one point to another.
149
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f. Check pressure differentials between the basement/subslab and
basement/upstairs as appliances (dryers, exhaust fans, furnace fans, etc.)
are cycled on and off.
g. Tracer gas measurements used to evaluate air exhange rates and
flows between zones.
Phase 3. Mitigation Installation Diagnostics.
a. Tracer gas measurements to determine leakage or backdraft of
exhaus t.
b. Adjust dampers for balanced air flow within the mitigation system.
c. Check the balance by measuring pressure differentials and the
velocities at key points in the mitigation system.
d. Integrity check of any building envelope components penetrated by
mitigation system.
Phase 4. Post-Mitigation Diagnostics.
a. Determine radon concentrations in different zones in the building.
b. Determine fan speed required for efficient radon removal, consider
energy aspects.
c. Check furnace draft for air flow direction, to insure that
combustion products are exiting properly.
150
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PART E REFERENCES
These references have been supplied by Dr. Allan Tanner.
References on Radon in Soil Gas, Diffusion, and Emanating Power
The following have been selected from among about 400 references.
Preference has been given to recent references that are particularly
relevant to radon migration to a structure foundation and to the variations
of radon in soil gas.A. B. Tanner, U. S. Geological Survey
Akerblom, G., P. Andersson, and B. Clavensjo, 1984
Soil gas radona source for indoor radon daughters:
Radiation Protection Dosimetry, v. 7, no. 1-4, p. 49-54
Xkerblom, Gustav, 1986
Investigation and mapping of radon risk areas:
Lulea, Sweden: Swedish Geological Co., Rept. IRAP 86036, 15 p. [To be
pub, in Geol. Survey Norway Special Papers]
Barretto, P[aulo] M. C., 1975
Radon-222 emanation characteristics of rocks and minerals, in Radon in
Uranium Mining:
Vienna, Internat. Atomic Energy Agency STI/PUB/391, p, 129-150
Bulashevich, Yu, P., and R. K. Khayritdinov, 1959
K teorii diffuzii emanatsii v poristykh sredakh [On the theory of diffusion
of emanations in porous media]:
Akad. Nauk SSSR Izvestiya, ser. Geofiz., no. 12, p. 1787-1792
Geophys. Abstracts no, 181-408
Clements, William E. and Marvin H. Wilkening, 1974
Atmospheric pressure effects on radon-222 transport across the Earth-air
interface:
Jour. Geophys. Research, v. 79, no. 33, p. 5025-5029
Colle, R., R. J. Rubin, L. I. Knab, and J. M. R. Hutchinson, 1981
Radon Transport Through and Exhalation from Building Materials; A Review
and Assessment:
U. S, National Bur. Standards Tech. Note 1139, 101 p. [Washington, GPO]
Culot, Michel V. J., Hilding G. Olson, and Keith J. Schiager, 1976
Effective diffusion coefficient of radon in concrete, theory and method
for field measurements:
Health Physics, v. 30, no. 3, p. 263-270
Eaton, R. S., and A. G. Scott, 1984
Understanding radon transport into houses:
Radiation Protection Dosimetry, v. 7, no. 1-4, p. 251-253
Barley, Naomi H., and Terence B. Terilli, 1986
Source term apportionment techniques for radon, in Indoor Radon, APCA
Internat. Specialty Conf. on Indoor Radon, Philadelphia, Pa., 24-26
February 1986, Proc.;
Pittsburgh, Pa., Air Pollution Control Assoc. Pub. SP-54, p. 13-24
151
-------
Hesselbom, Ake, 1984
Radon in soil gas: A study of methods and instruments for determining
radon concentrations in the ground:
Uppsala, Sveriges geologiska undersokning, ser. C, no. 803, p. 1-58 [1985]
Jeter, Hewitt W., J. David Martin, and Donald F. Schutz, 1977
The migration of gaseous radionuclides through soil overlying a uranium
deposit: a modeling study:
U.S. Dept. of Energy Rept, GJBX-67: 44 p.
Kapustin, 0, A., and K. B. Zaborenko, 1978
K teorii emanatsionnogo metoda:
Radiokhimiya, v, 20, no. 2, p. 276-283; translated into English as Theory
of the emanation method:
Soviet Radiochemistry, v. 20, no. 2, p, 235-242
Chem. Abstracts 88:197876m
Kraner, Hofaart W,, Gerald L. Schroeder, and Robley D. Evans, 1964
Measurements of the effects of atmospheric variables on radon-222 flux
and soil gas concentrations, in Adams, John A. S., and Lewder, Wayne
M. eds., The Natural Radiation Environment:
Chicago, Chicago Univ. Press: p, 191-215
Lindmark, A., and B. Rosen, 1985
Radon in soil gasexhalation tests and in situ measurements:
Science of the Total Environment, v. 45, p, 397-404
Makofske, William J,, and Michael R. Edelstein, eds., 1987
Radon and the Environment, Conference Proceedinas, Mahwah, N. J., Mav
8-10, 1986:
Mahwah, N. J., Ramapo College of New Jersey, Inst, for Environmental
Studies, 470 p.
Megumi, Kazuko and Tetsuo Mamuro, 1974
Emanation and exhalation of radon and thoron gases from soil particles;
Jour. Geophys. Research, v. 79, no. 23, p. 3357-3360
Mochizuki, Sadamu, and Toshio Sekikawa, 1980
Radon-222 exhalation and its variation in soil air, in Gesell, Thomas
F., and Wayne M. Lewder, eds., Natural Radiation Environment III:
Springfield, VA, NTIS, U. S. Dept. Energy Rept. CONF-780422, Vol. 1,
p. 105-116
Nazaroff, W. W. , H. Feustel, A. V. Nero, K. L. Revzan, D. T. Grimsrud,
M. A. Essling, and R. E. Toohey, 1985
Radon transport into a detached one-story house with a basement:
Atmospheric Environment, v. 19, no, 1, p. 31-46
Nero, A. V,, R. G. Sextro, S, M. Doyle, B. A. Moed, W, W. Nazaroff, K, L.
Revzan, and M. B. Schwehr, 1985
Characterizing the sources, range, and environmental influences of radon-
222 and its decay products:
Science of the Total Environment, v. 45, p. 233-244
152
-------
Nielson, K. K., V. C. Rogers, and G. W. Gee, 1984
Diffusion of radon through soils: a pore distribution model:
Soil Sci. Soc. America Jour., v. 48, no. 3, p. 482-487
Rogers, V. C., K. K. Nielson, and D. R. Kalkwarf, 1984
Radon Attenuation Handbook for Uranium Mill Tailings Cover Design:
U. S. Nuclear Regulatory Commiss. Rept. NUREG/CR-3533, 85 p.
Rubin, R. M., 1978
Literature Survey on Radon Distribution in Soil and Air; Final Report:
U. S. Dept. Energy Rept. GJBX-110(80), 63 p.
Rudakov, V. P., 1985
K voprosu o prirode sezonnykh variatsiy podpochvennogo radona;
Geokhimiya, no. 7, p. 1055-1058; in English translation, 1986
Nature of the seasonal variations in subsoil radon:
Geochemistry Internat., v, 23, no. 1, p. 133-136
Sachs, H. M,, T. L. Hernandez, and J, W. Ring, 1982
Regional geology and radon variability in buildings:
Environment Internat., v. 8, no. 1-6, p. 97-103
Schery, S. D., and D. H. Gaeddert, 1982
Measurements of the effect of cyclic atmospheric pressure variation on
the flux of 222j^ from the soil:
Geophys. Research Letters, v. 9, no. 8, p. 835-838
Schery, S. D., D. H. Gaeddert, and M. H. Wilkening, 1984
Factors affecting exhalation of radon from a gravelly sandy loam:
Jour. Geophys. Research, v. 89, no. D5, p. 7299-7309.
Schery, S. D., and D. Siegel, 1986
The role of channels in the transport of radon from the soil:
Jour. Geophys. Research, v. 91, no. B12, p. 12,366-12,374
Schmied, Hannes, 1985
Combined stack effect in houses and eskers explaining transients in radon
source:
Science of the Total Environment, v. 45, p. 195-201
Sextro, R. G., B. A. Moed, W. W. Nazaroff, K. L. Revzan, and A. V. Nero,
1987
Investigations of soil as a source of indoor radon, in Hopke, Philip
K., ed., Radon and Its Decay Products; Occurrence, Properties, and
Health Effects:
Washington, Am. Chem. Soc. Symposium Ser. 331, p. 10-29
Soonawala, N. M., and W. M. Telford, 1980
Movement of radon in overburden:
Geophysics, v. 45, no. 8, p. 1297-1315
153
-------
Stieff, L. R., C. B. Stieff, and R. A. Nelson, 1987
Field measurements of in situ 222Rn concentrations in soil based on the
prompt decay of the 214gi counting rate:
Nuclear Geophysics [Internat. Jour. Applied Radiation Isotopes, Pt. E.],
v. 1, no. 2, p, 183-195
Taipale, T. T., and K. Winqvist, 1985
Seasonal variations in soil gas radon concentration:
Science of the Total Environment, v. 45, p. 121-126
Tanner, Allan B., 1980
Radon migration in the ground: a supplementary review, .in Gesell, Thomas
F., and Wayne M. Lowder, eds., Natural Radiation Environment III:
Springfield, VA, NTIS, U. S. Dept. Energy Rept. CONF-780422, Vol. 1,
p. 5-56.
Tanner, Allan B., in press
Measurement of radon availability in soil, _in Georad Conference on Geologic
Causes of Natural Radionuclide Anomalies, St. Louis, Mo., 21-21 April
1987, Proc.:
Rolla, Mo., Missouri Dept. Nat. Resources, Div. Geology and Land Survey
Wilkening, Marvin H., 1980
Radon transport processes below the Earth's surface, in Gesell, Thomas
F., and Wayne M. Lowder, eds., Natural Radiation Environment III:
Springfield, VA, NTIS, U. S. Dept. Energy Rept. CONF-780422, Vol. 1,
p. 90-103, disc., p. 103-104
Wilkening, Marvin, 1985
Radon transport in soil and its relation to indoor radioactivity:
Science of the Total Environment, v. 45, p. 219-226
Zimens, K. E., 1943
Surface area determinations and diffusion measurements by means of radio-
active inert gases. Part III. The process of radioactive emission
from disperse systems. Conclusions pertaining to the evaluation of
EP (emanating power) measurements and the interpretation of results
[in German]:
Zeitschr. Physik. Chemie, v. 192, no. 1/2, p. 1-55 in English translation,
East Orange, New Jersey, Assoc. Tech. Services, no. 43G7G, 38 p. [1955]'
154
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Radon Contributions from the Mining Industry
Bates, Robert C., 1977
Rock sealant restricts falling barometer effect:
Mining Engineering, Dec. 1977, p. 38-39
"These analyses demonstrate that radon contamination resulting from
a change in barometric pressure is reduced by a rock [sealant] coating.
This, however, is not the major fact to be kept in mind. More impor-
tant is that, despite the imperfection in the coatings, the radon
concentration in the mine atmosphere was reduced through the use of
coatings by more than 70% from an average of 480 to 140 [pCi/L]."
Bates, Robert C., 1977
Sealants restrict barometric pressure effects:
Mining Engineering, 29(12); 38-39
Bates, Robert C., 1980
Time dependent radon loss from small samples
Health Physics, 39: 799-801
In connection with a study of the effect of moisture on the radon emanation
coefficient in small uranium ore.samples, the question arose about
the time needed to reach a steady-state flux of radon from a sample
after opening of its sealed storage and counting can. It was felt
intuitively that the time required to reach equilibrium would depend
on the pore-filling fluid-and the diffusion coefficient. No evaluation
of this effect was found in the literature. A previously developed
analytical code was used with a cylindrical model 9,2 cm long and
3.843 cm in radius, 0.2 porosity, 1E-7 cm"2 permeability, 300 K, and
pore-fluid viscosity of 1.8E-4 g/cm-s. The periods required to reach
a steady-state flux were computed to be 0,25, 1.25, 10.0, 70,0, and
>100.0 hours, respectively, for diffusion coefficients of 1E-2, 1E-3,
1E-4, 1E-5, and 1E-6 cm~2/s.
Bates, Robert C., and John C. Edwards, 1978
Radon emanation relative to changing barometric pressure and physical
constraints, in Conference en Uranium Mining Technology, Second, Reno,
Nev., November 13-17, 1978:
Background is given on the various equations used to describe diffusion
and convective flow of radon in porous media. Equations developed
by the Bureau of Mines for modeling diffusion and Darcy flow through
multilayered porpus media are described briefly and examples of their
use are given. Cases evaluated include overpressurization, underpres-
surization, and cyclic pressurization of different-sized ore bodies.
Another part of the analysis deals with the effect of pinholes on
the effectiveness of a radon barrier coating.
Bates, Robert C., and John C. Edwards, 1981
The effectiveness of overpressure ventilation: a mathematical study,
in Gomez, Manuel, ed., Radiation Hazards in Mining: Control, Measurement,
and Medical Aspects, International Conference, Golden, Colo October
4-9, 1981:
Golden, CO, Colorado School of Mines, Chap. 24, p. 149-154
Results are given of a mathematical study of overpressurization ventila-
tion effects in underground uranium mines. The mathematics and conputer
155
-------
codes make it possible to analyze many facets of transient and steady-
state radon diffusion with Darcy flow. Rapid changes in radon flux
occur after imposing a pressure differential across the model. Flux
into the model mine drops to near zero and then increases to the steady
state level, while the sink flux increases rapidly and then drops
slightly to the steady-state level. Magnitudes of mine flux decreases
and sink flux increases are dependent upon the distance from the mine
to sink, permeability, and the amount of overpressure.
Bates, Robert C,, and John C. Franklin, 1977
U. S. Bureau of Mines radiation control research, in Conference on Uranium
Mining Technology, Reno, Nev., April 25-29, 1977:
Efforts by the Bureau of Mines to measure and reduce harmful concentrations
of radioactive gas in uranium mines are discussed. Equipment has
been developed for simultaneous monitoring of radon and radon daughters,
temperature, relative humidity, absolute pressure, and air velocity.
The effects of changes in weather conditions, ventilation, and mining
methods on the mine atmosphere can therefore be evaluated. Addition
of water to the rock substantially increases the radon emanation from
rock walls. Control methods being evaluated include overpressurization,
cyclic ventilation, bulkheading, backfilling with tailings, and application
of sealants to the mine rock.
Bates, R. C., and R. L. Rock, 1962
Estimating Daily Exposures of Underground Uranium Miners to Airborne
Radon-Daughter Products:
U. S. Bur. Mines Rept. Investigations 6106, 22 p.
Droullard, R. F., T, H. Davis, E. E. Smith, and R. F. Holub, 1984
Radiation Hazard Test Facilities at the Denver Research Center:
U. S. Bur. Mines Inf. Circ. 8965, 22 p.
The Bureau of Mines has developed test facilities for use in a research
program that deals with radiation hazards in mining. This report
describes the radon test chamber located at the Denver Research Center
and the Twilight experimental mine located near Uravan, CO.
Droullard, R. F., and R. F. Holub, 1977
Continuous Working-Level Measurements Using Alpha or Beta Detectors;
U, S. Bur. Mines Rept. Investigations 8237, 14 p.
The Bureau of Mines has investigated techniques of using gross alpha
or beta detectors to continuously measure working levels. Both methods
measure radioactive particulates collected on a filter paper usina
a constant airflow. Inherent-err or studies indicate a value of about
+/- 3 percent for the gross alpha method and about +/- 8 percent for
the beta method in typical mine atmospheres. However, the beta method
avoids problems associated with alpha detectors and is therefore more
useful. Applications of these continuous working-level detectors
include work area monitoring of exposure levels in underground openinas,
such as mines and caves, and calibrating personal dosimeters exposed
over extended time intervals.
Droullard, R. F., and R. F. Holub, 1985
Continuous Radiation Working-Level Detectors;
U. S. Bur. Mines Inf. Circ. 9029, 20 p.
156
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The Bureau of Mines has used gross alpha and gross beta detectors to
continuously measure radiation working levels for a number of years,
During this time, improvements have been made in the design and per-
formance of continuous working-level (CWL) detectors. This report
discusses the improved designs and some of the operating principles
and applications of CWL detectors in the measurement of radon daughter
products in mines and dwellings.
Edwards, John C., and Robert C. Bates, 1980
Theoretical evaluation of radon emanation under a variety of conditions:
Health Physics, 39: 263-274
Franklin, JohnC., 1981
Control of radiation hazards in underground uranium mines, in Gomez.
Manuel, ed. , Radiation Hazards in Mining: Control, Measurement, and
Medical Aspects, International Conference, Golden, Colo., October
4-9, 1981:
Golden, CO, Colorado School of Mines, Chap, 69, p. 441-446
Franklin, J. C., R. C, Bates, and J, L. Habberstad, 1975
Polymeric sealants may provide effective barriers to radon gas in uranium
mines:
Engineering Mining Jour., 176(9): 116-118
Franklin, JohnC., and Randall F. Marquardt, 1976
Continuous radon gas survey of the Twilight Mine:
U. S. Bur. Mines, Metal-Nonmetal Health and Safety/Health Program, Tech.
Prog. Rept. 93, 16 p.
Franklin, John C., Thomas 0. Meyer, and Robert C. Bates, 1977
Barriers for Radon in Uranium Mines:
U. S. Bur. Mines Rept. Inv. 8259, 24 p.
Water-based epoxy sealants were examined during a 2-year period to deter-
mine their effectiveness as barriers to radon release in uranium mines.
Radon emanation rates from uranium ore samples were monitored for
extended periods in the laboratory before and after sealant appli-
cation. Reduction of radon flux due to the coating of laboratory
samples was approximately 80 percent. Test chambers in a dormant
uranium mine were monitored to determine both short and long-term
barrier effectiveness. These field studies of the sealants indicated
radon flux reductions exceeding 50 percent relatively soon after appli-
cation and nearly 75 percent about 1 year later. An unexpected compli-
cation to early monitoring in the form of a large radon emanation
increase, believed due to added moisture, is discussed.
Franklin, J. C., T. 0. Meyer, R. W. McKibbin, and J. C. Kerkering, 1976
A continuous radon survey in an active uranium mine;
Mining Engineering, 30(6): 647-649
Franklin, J. C., C. S. Musulin, and R. C. Bates, 1980
Monitoring and control of radon hazards, in International Mine Ventila-
tion Congress, 2d, Reno, Nev,:
Proceedings, p. 405-411
157
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Franklin, John C., Lee T. Nazum, and Adare L. Hill, 1975
Polymeric Materials for Sealing Radon Gas Into the Walls of Uranium
Mines:
U, S. Bur. Mines Kept. Investigations 8036, 26 p.
The Bureau of Mines conducted extensive laboratory and limited field
tests to determine whether a polymeric material could effectively
reduce the emanation rate of radon gas from uranium ore. In the labor-
atory 46 different single-coat materials and 14 two-coat applications
were tested. The laboratory tests showed that up to 100 percent of
the radon gas could be sealed into the rock. Materials tested in
the laboratory were polyesters, furan resins, epoxies, latices, and
totally inorganic coatings. From the laboratory work six different
materials were selected for field testing. The first test was single-
coat materials in five static chambers; the second test used two-coat
applications in an open chamber. Both tests were conducted in the
Dakota mine at Grants, N. M. During the second test, the emanation
rate of radon was reduced up to 62 percent.
Franklin, J. C., R. J. Zawadski, T. 0. Meyer, and A. L. Hill, 1976
Data-Acquisition System for Radon Monitoring:
U. S. Bur. Mines Rept. Investigations 8100, 19 p.
A data-acquisition system was designed by the Bureau of Mines to monitor
five detectors with radon continuously flowing through each. These
detectors could be monitored up to 12 times an hour, but were only
monitored according to a preset time, thus allowing radon to be moni-
tored continuously in a uranium mine. The counter can be set to moni-
tor each detector for any period of time up to 16.5 minutes. This
allows very low concentrations to be monitored longer to reduce statis-
tical error. There would be no upper limit in radon concentration
that could be monitored, but there would be a lower limit of 50 pCi/L.
Each detector was calibrated in the laboratory by the Lucas flask
method. Multiple samples were taken at two different concentrations,
and the correction factors for each detector was determined by a least
squares fit of the data. To verify the calibrations, a series of
measurements at several concentrations (300 pCi/L) with the two-filter
method was within 3 percent; thus, the total error would be this dif-
ference plus the two-filter error. At high concentrations the coeffi-
cient of variation ranged between 2.1 and 9.8 percent for the five
different detector units.
Holub, R. F., 1984
Turbulent plateout of radon daughters:
Radiation Protection Dosimetry, 7(1-4); 155-158
CA 101;99840n
Holub, R. F., and P. J. Dallimore, 1981
Factors affecting radon transport and the concentration of radon in
mines, In Gomez, Manuel, ed., Radiation Hazards in Mining: Control,
Measurement, and Medical Aspects, International Conference Golden'
Colo., October 4-9, 1981:
Golden, CO, Colorado School of Mines, Chap. 154, p. 1022-1028.
".. .The laboratory experiments performed involved measurements of diffusion
and emanation coefficients, porosity and permeability of representative
rock samples. Significant differences have been found when comparing
158
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the results of the laboratory permeability determinations to those
of the mine determinations. Considerations of underlying principles,
however, suggest that the diffusion and emanation coefficients are
the same in laboratory and mine. It was also found that moisture
content plays a dominant role in radon transport through rock,.,."
Holub, R. F., and R. F. Droullard, 1978
Radon Daughter Mixture Distributions in Uranium Mine Atmospheres:
U. S. Bur. Mines Rept. Investigations 8316, 20 p.
The Bureau of Mines has made a study of the magnitude of the variations
of radon daughter mixtures, with the objective of determining whether
these variations reflect the existing physical conditions in uranium
mine atmospheres or if they are merely random or systematic errors.
To accomplish this, many data have been plotted using a triangular
graphing technique which shows that plateout affects Po-218 more than
Pb-214 or Bi-214, and that it is impossible to find simple correlations
between working level ratios, radon daughter mixtures, and age.
Holub, R. F., R. F. Droullard, T. B. Borak, W. C. Inkret, J. G. Morse,
and J. F. Baxter, 1985
Radon-222 and Rn-222 progeny concentrations measured in an energy-effi-
cient house equipped with a heat exchanaer:
Health Physics, 49(2): 267-277
McVey, James R,, John C. Franklin, and David M, Shaw, 1977
Portable instrument measures four ventilation parameters:
Mining Congress Jour., 63(4): 49-52
A four-parameter measurement system for accurate determination of relative
humidity, temperature, mine pressure and ventilation velocity has
been developed for use in the radon control research of the U. S. Bureau
of Mines. The new unit is housed in a 17-by 20- by 8-in. suitcase
weighing less than 15 pounds.
Additional references:
Hammon, J. G., K. Ernst, J. R. Guskill, J. C. Newton, and C. J. Morris,
1975
Development and evaluation of radon sealants for uranium mines:
Livermore, Calif., Lawrence Livermore Lab., U. S. Bur. Mines Contract
Rept. H0232047, 67 p.
Lindsay, D. B., G. L. Schroeder, and C. H. Summers, 1981
Polymeric wall sealant test for radon control in a uranium mine, in
Gomez, Manuel, ed., Radiation Hazards in Mining: Control, Measurement,
and Medical Aspects, International Conference, Golden, Colo., October
4r9, 1981:
Golden, CO, Colorado School of Mines, Chap. 118, p. 790-793
Schroeder, G. L., 1977
Falling barometer nullifies rock sealant effectiveness:
Mining Engineering, 29(6): 38-39
159
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Strong, Kaye P., Desmond M. Levins, and Anthony G. Fane, 1981
Radon diffusion through uranium tailings and earth cover, in Gomez,
Manuel, ed., Radiation Hazards in Mining: Control, Measurement, and
Medical Aspects, International Conference, Golden, Colo., October
4-9, 1981:
Golden, CO, Colorado School of Mines, Chap. 107, p. 713-719
160
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F. ATTENDEES RADON DIAGNOSTICS WORKSHOP
Jorge Berkowitz, Director (J.B.)
Div. of Environmental Quality
NJ Dept. of Environmental Protection
401 East State Street
Trenton, NJ 08625
William Belanger (W.Be)
EPA, Region III
841 Chestnut Street
Philadelphia, PA 19107
215-5977-4084
David Bohac (D.B.)
CEES/EQUAD
Princeton University
Princeton, NJ 08544
609-452-4665
William Brodhead (W.B.)
R.D. #1 Box 209
Riegelsville, PA 18077
215-346-8004
Terry Brennan (T.B.)
Camroden Assoc. Inc.
R.D. #4
Box 62
Rome, NY 13440
315-865-4269
Mary Cahill (M.C.)
Bureau of Radiation Protection
CN 411
N.J. DEP
Trenton, NJ 08625
609-530-4000
A. B. Craig
US EPA (MD-60)
RTF, NC 27711
919-541-2821
(A.C.)
(W.C.)
William Connoly
Deputy Director
Division of Housing & Development
Dept. of Community Affairs
Trenton, NJ 08628
609-292-7899
Jay Davis (J.D.)
Camp, Dresser & McKee
Raiton Plaza
Edison, NJ 08817
201-225-7000
Craig Decker (C.D.)
CEES/EQUAD
Princeton University
Princeton, N.J. 08544
609-452-5445
Nick DePierro (N.D.)
NJ Dept. of Envir. Protection
32-A Collis Lane
Chester, NJ 07930
201-879-2492
Charles S. Dudney (C.D.)
Oak Ridge Natl. Lab.
Health & Safety Res. Div.
Oak Ridge, TN 37830
Gene Fisher (G.F.)
Radon Detection Services, Inc.
P.O. Box 419
Ringoes, NJ 08551
201-788-3080
Kenneth Gadsby (K.G.)
CEES/EQUAD
Princeton University
Princeton, NJ 08544
609-452-5466
Susan Galbraith (S.G.)
Cogito Technical Services
P.O. Box 86
Sheds, NY 13151
315-662-7529
.Richard Gammage (R.G.)
Health & Safety Research Div.
Bldg. 4500S MS S258
Oak Ridge National Laboratory
Oak Ridge, TN 37831
615-574-6256
161
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Thomas M. Gerusky (T.G.)
Bureau of Radiation Protection
Department of Envir. Resources
P.O. Box 2063
Harrisburg. PA 17120
Paul Giardina
EPA, Region II
26 Federal Plaza
New York, NY 10278
(P.G.)
Carl Granlund (C.G.)
Bureau of Radiation Protection
Department of Environ. Resources
P.O. Box 2063
Harrisburg, PA 17120
717-787-2480
Bruce Harris
US EPA TAB (MD-54)
RTP, NC 27711
919-596-4054
(B.Ha.)
Jed Harrison (J.Har)
Indoor Environment, Bldg. 90-3058
Lawrence Berkeley Lab
Berkeley, CA 94720
415-486-5343
David T. Harrje (D.H.)
CEES/EQUAD
Princeton University
Princeton, NJ 08544
609-452-5190
Tim Hartman (T.H.)
Radon Monitoring Program
Department of Envir. Resources
1100 Grosser Rd.
Gilbertsville, PA 19525
215-369-3590
J.P. Harper (J.Ha)
Division of Conserva. & Energy Mgt.
Tennessee Valley Authority
3N51A Signal Place
Chattanooga, TN 37402-2801
615-751-7007
Frank Haughey
Radiation Science Program
Rutgers University
New Brunswick, NJ 08903
(A.Ha)
Alan Hawthorne (A.H.)
Health & Safety Research Div.
Bldg. 4500S MS 126
Oak Ridge National Laboratory
Oak Ridge, TN 37831-6126
615-576-2083
Bruce Henschel (B.H.)
U.S. EPA - IAB (MD-54)
RTP, NC 27711
919-541-4112
Eileen Hotte (E.H.)
Bureau of Radiation Protection
CN 411
N.J. DEP
Trenton, NJ 08625
609-530-4001
Jou Hwang (J.H.)
Bureau of Radiation Protection
NJ DEP
32-A Collis Lane
Chester, NJ 07930
201-879-2492
Lynn Hubbard (L.H.)
CEES/EQUAD
Princeton University
Princeton, NJ 08544
609-452-6424
Earl Knudson (E.K.)
US DOE Environmental
Measurements Laboratory
376 Hudson Street
NY, NY 10014
212-620-3655
Larainne Koehler (L.K.)
EPA, Region IX
26 Federal Plaza
New York, NY 10278
(212) 264-4418
Michael D. Koontz (M.K.)
GEOMET Technologies
20251 Century Blvd.
Germantown, Md 20874
301-428-9898
162
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Wayne Lowder (W.L.)
DOE. EML
376 Hudson Street
New York, NY 10014
212-660-3631
Michael Mardis (M.M.)
Radon Action Program
Office of Radiation Programs
401 M Street, SW
Washington, DC 20460
202-475-9605
Wiktor Marek (W.M.)
Dept. of Computer Science
University of Kentucky
915 Patterson Office Tower
Lexington, KY 40506
606-257-3496
Thomas Matthews (T.M.)
Oak Ridge National Labs
Health 6c Safety Research Div.
Building 4500 South
Oak Ridge, TN 37831
615-574-6248
Marc Messing
Infiltec
1105 Park St., NE
Washington, DC 20002
Ronald Mosley
US EPA - IAB (MD-54)
RTP, NC 27711
919-541-7865
Anil Nerode, Chairman
Dept. of Mathematics
Cornell University
White Hall, Room 233
Central Avenue
Ithaca, NY 14853
607-255-3577
Ian Nitschke
W.S. Fleming Association
6310 Fly Rd.
East Syracuse
New York 13057
315-437-1870
(M.Me)
(R.M.)
(A.N.)
(I.N.)
Robert Oliver (R.O.)
Supervisor, Bldg. Energy Sciences
U.S. Dept. of Energy
CE-131
1000 Indep. Ave., SW
Washington, DC 20585
202-586-9455
Michael Osborne (M.O.)
US EPA - IAB (MD-54)
RTP, NC 27711
929-541-4113
Thomas Feake (T.P.)
Radon Action Program
Office of Radon Programs
401 M Street, SW
Washington, DC 20460
202-475-9605
.Richard Prill (R.P.)
Lawrence Berkeley Lab
1 Cyclotron Road
Berkeley, CA 94720
415-486-7326
Michael Pyles (M.P.)
Radon Monitoring Program
Dept. of Envir. Resources
'1100 Grosser Road
Gilbertsville, PA 19525
215-369-3590
1-800-237-2366 in PA
John Reese (J.R.)
NYS ERDA
2 Empire State Plaza
Albany, N.Y. 12257
518-473-7243
Mary Reilly (M.R.)
Div. of Housing & Development
Dept. of Community Affairs
FCN 805
Trenton, NJ 08628
09-633-2114
163
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/9-89-057
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Proceedings of the Radon Diagnostics Workshop,
April 13-14, 1987
5. REPORT DATE
June 1989
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
David T. Harrje and Lynn M. Hubbard, Compilers
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Princeton University
Center for Energy and Environmental Studies
Princeton, New Jersey 08544
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
CR814014-01-0
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Proceedings; 3/87 - 2/88
14. SPONSORING AGENCY CODE
EPA/600/13
15.SUPPLEMENTARY NOTES AEERL project officer is David C. Sanchez, Mail Drop 54, 919/
541-2879.
is. ABSTRACT
proceec[ings document a two-day radon diagnostics workshop at Prince-
ton University, April 13-14, 1987. The proceedings comprise a consensus of cur-
rent knowledge on important radon diagnostic techniques and how they may best be
applied. That knowledge is summarized, placing the various radon diagnostic tech-
niques in perspective. Diagnostic approaches offer improved evaluations of radon-
related indoor air quality problems. An informed solution involves knowledge of the
building, the building site, and the interaction of radon sources with the living space.
The diagnostics are applicable in four phases of the mitigation process: (l) diagnos-
tics that assess the radon problem; (2) premitigation diagnostics, from which a
suitable mitigation approach must be selected; (3) diagnostics that check the perfor-
mance of the radon mitigation solution; and (4) diagnostics that determine if the ra-
don problem has been solved and that guideline radon concentrations have not been
exceeded over the different seasonal conditions experienced.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Radon
Diagnosis
Buildings
Atmospheric Contamination Control
Pollution Control
Stationary Sources
Indoor Air Quality
Building Sites
13B
07B
06E
13 M
06K
13. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
170
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
164
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