United States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
EPA/625/6-91/032
April1991
Technology Transfer
vvEPA Handbook
Assessment Protocols
Durability of
Performance of a Home
Radon Reduction System
Sub-Slab Depressurization
Systems
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EPA/625/6-91/032
April 1991
Handbook
Assessment Protocols
Durability of Performance of a
Home Radon Reduction System
Sub-Slab Depressurization Systems
by
Kenneth J. Gadsby and David T. Harrje
Center for Energy and Environmental Studies
Princeton University
Princeton, NJ 08544
Cooperative Agreement No. CR-814673
EPA Project Officer
David C. Sanchez
Radon Mitigation Branch
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
Prepared for
U. S. Environmental Protection Agency
Office of Research and Development
Washington, DC 20460
Printed on Recycled Paper
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Disclaimer
Mention of trade names or commercial products in this document does not constitute
EPA endorsement or recommendations for their use.
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Abstract
The purpose of these protocols is to provide a methodology to test subslab depres-
surization (SSD) radon mitigation systems in-situ to determine the long-term performance
of these systems. There had been no organized research effort undertaken to develop
these state-of-the-art protocols at the time of the start of this project in October 1987. The
research project continued until March 1990. Durability of SSD radon mitigation systems
in the context of this report compares the performance of the mitigation system immedi-
ately after installation to operating conditions at'later time intervals of months or years.
The methodology includes occupant interviews and various parametric measurements
with which the performance of the mitigation system can be evaluated. The major basis
of comparison is the radon levels in the building. Other post-installation data, such as
system flow rates or pressures, will be used in the assessment of durability of perfor-
mance. Results of the testing during the development of these protocols point out two
important findings: first that occupant interaction with the mitigation system'can result in
elevated radon levels; and second that most of the SSD mitigation systems are operating
as designed 3.5 years after installation.
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Scope
These procedures describe standardized techniques for the assessment of durability
of performance,of in-situ subslab.depressurization (SSD) radon mitigation systems.
Some of these procedures require a knowledge of airflow measurement in pipes,
pressure differential measurements, radon measurements, and residential building con-
struction. • • ' '-''• .' •' ' -'•''• ,
These procedures are, of ,a qualitative nature |n determining the current operating
condition of the mitigation system rather than determining the predicted longevity of the
system. , ' , • . " .,_.',, ".• "'.'.'.
These procedures may involve hazardous operations "and do not purport to address
all the safety hazards associated with their use.' It is the responsibility 'of whoever uses
these procedures to consult the applicable documents and manuals for the equipment
used and establish appropriate safety and health practices before their use.
IV
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Table of Contents
Abstract • •••••••• • )"
Scope - ••' >. - iy
Acknowledgements • • • yj
Metric Equivalents - • •• • ••••• • • Vli
1. Introduction and Background ....1
1.1 Theory of Operation of SSD Systems 1
1.2 Operational Environment • 1
2. Objectives • • 3
3. Conclusions • 5
4. Recommendations 7
5. The Approach for Durability Testing • 9
6. Procedures 11
6.1 Pre-house Visit 11
6.2 House Visit - - - 11
7. Apparatus • • 15
8. Results • • • • 17
8.1 Results from the New Jersey Piedmont Houses 17
8.2 Results from the NJDEP Houses ...24
8.3 Durability Data from other Research Groups 25
8.4 QA/QC Statement -26
9. References 27
10. Appendix A. Radon Durability Diagnostics Forms .29
Appendix B. Measurement Equipment Used in This Study....: 37
Glossary 39
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Acknowledgments
This work was funded by the U.S. Environmental Protection Agency under Coopera-
tive Agreement CR-814673. We would like to acknowledge the efforts of: Tonalee Key
and other personnel of NJDEP, Radon Research/Outreach Section, in providing the
NJDEP candidate houses; Charles Fowler of Southern Research Institute and Charles
Dudney of ORNL for providing data from their research houses; Richard Gafgen of our
research group who took many of the measurements; and especially the cooperative
owners for allowing the many visits necessary to gather these data.
VI
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Metric Equivalents
Metric
centimeter (cm)
centimeter (cm)
meter (m)
square meter (m2)
liter (L)
cubic meter (m3)
liter per second (L/sec)
Pascal (Pa)
Becquerel per cubic meter
(Bq/m3)
degree Centigrade (°C)
Multiply by
0.39
0.033
3.28
10.76
0.35
35.31
2.12
0.004
0.027
(9/5°C)+32
Yields nonmetric
inch (in.)
foot(tt)
foot (ft)
square foot (ft2)
cubic ft (ft3)
cubic ft (ft3)
cubic foot per minute (cfm)
inch of water column (in. WC)
picocurie per liter (pCi/L)
degree Fahrenheit (°F)
vii
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Section 1
Introduction and Background
There is increasing evidence that the health risks in
those houses with significant levels of radon (above
the EPA action level of 4 pCi/L) may constitute the
most serious indoor air quality problem in the United
States. Radon intrusion is often pictured as a seasonal
phenomenon, with stack effect and other pressure-
driven factors influencing soil gas entry to building sub-
structures. Several solutions have been proposed.
These approaches involve energy use as well as in-
door air quality concerns. The proposed solutions must
be tailored for the specific nature of the radon source.
If the radon enters the house via the well water, one
approach is necessary; radon in building materials may
suggest other strategies. In this protocol, our attention
will be focused on radon entry with soil gas through the
building substructure, and what that mechanism implies
for radon mitigation.
Even limiting our scope to soil gas entry, many
solutions exist to reducing radon concentrations in the
house. Local exhaust is one strategy. Ventilation used
to dilute the radon concentrations and building pressur-
ization are some other options. Each approach must
be matched to a given radon condition in the individual
building. This protocol will consider only the method
known as subslab depressurization (SSD). This mitiga-
tion approach has been proven to be very effective,
often decreasing indoor radon concentrations by 90%
or more following mitigation.
1.1 Theory of Operation of SSD Systems
for Radon Mitigation
The theory of operation for the SSD system is that
by penetrating the concrete floor slab with an exhaust
pipe one gains access to the area beneath the slab.
The area, often a gravel bed, serves as a collection site
for the soil-gas-containing radon. The exhaust pipe is
then routed to the outside of the building, typically
through the roof. The negative pressure provided by
the exhaust pipe reduces the convective flow of soil
gas into the building and causes the soil gas to be
removed from the subslab area. If communication ex-
ists between the subslab volume and the walls of the
building, soil gas will simultaneously be exhausted from
the walls. The exhaust mechanism can be passive,
which implies that suction pressures beneath the slab
will vary seasonally, with the greatest suction occurring
during the coldest weather due to increased buoyancy
of the air in the vertical exhaust stack (if it is routed
through the inside of the building). In the systems
tested in this research, exhaust fans are used. These
"active systems" were shown to maintain near constant
suction pressures under the slabs during the entire
year.
The key point to remember, in the merits of year-
round radon removal, is that there is no guarantee that
radon problems will not be present even in the summer
months. The radon levels found in individual houses
are a complex result of radon source strength, soil
transport, the number, size, and location of entry points,
weather, and the way the house is operated. To be
certain of maintaining low radon levels in the house
normally requires that a SSD mitigation system work
properly 24 hours per day, 365 days per year. It is for
this reason that durability and system performance are
such important considerations. Performance level goals
are for 100% on-time operation for the life of the
building. This requires excellent durability of system
components and a reliable means for determining
whether the system is fully operational at all times.
The lack of'long-term data on SSD systems is a
major obstacle in determining whether the SSD sys-
tems perform adequately. This project has been di-
rected toward gathering such data from eight research
houses that were part of the Piedmont Study (Ref.2),
also houses tested by the New Jersey Department of
Environmental Protection, Florida (Southern Research
Institute) research houses, and Tennessee (ORNL) re-
search houses, as a follow-up lo mitigation activities.
1.2 Operational Environment
The question of durability of the mitigation system
arises not only from the need for lifetime operation in
the house, but concerns about tlhe environment to which
the SSD system is subjected (Refs. 3 and 4). Soil gas
is often very humid, causing condensation problems in
the piping and the fan of the mitigation system. Also,
particles can be drawn from the gravel bed or soil; they
in turn may line the pipes and deposit on the fan or
possibly interfere with the fan bearings.
The moisture removal from the subslab can be very
substantial, and could amount to many gallons of water
per day (Refs. 3 and 4). Unless the piping design
allows for that water to drain back into the soil, the
water could block flow of air in the piping or interfere
with the fan operation. Evidence of the moisture and
other debris has also been found in the staining of
roofs near the exhaust pipes of the SSD systems.
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The amount of sand and other particles sucked
from the soil must be viewed as a possible cause for
bearing failure or for the generation of bearing noise
(such effects also can be caused by the moisture).
Noise can directly influence the occupant to shut down
the SSD system. Sandblasting of the fan blades or
plateout on the fan blades by particles sucked into the
mitigation system could lead to degradation of fan per-
formance over the long term.
Another environmental effect that should not be
overlooked is the amount of airflow through the fan. To
remain at an appropriate operating temperature re-
quires sufficient airflow to remove fan motor heat. Fan
motor capacitor failure will cause the motor to operate
at a lower speed and efficiency, especially after the
motor has been shut off by the occupant or electrical
power interruption. Operating the fan in either of these
modes will lead to higher radon levels in the living
space and invites early fan failure.
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Section 2
Objectives
A. Our first objective has been to document the
ability of the SSD radon mitigation system to maintain
houses at radon concentration levels below the current
EPA action level of 4 pCi/L In these measurements
we hoped to observe the influence of parameters such
as seasonal factors. The effect of local weather such
as rain storms is the subject of more detailed radon
monitoring in test houses (Ref. 2).
B. A second objective was to observe the long-
term characteristics of radon levels in the SSD system
exhaust. Source strength and transport properties of
the soil may be determined from these measurements.
Also, comparisons between the natural flow of radon
through the building and the amount being exhausted
by the mitigation can be made.
C. A third objective was to evaluate the long-term
influences of the SSD system operation on the house
substructure. Since we are concerned about lifetime
operation we need to know more about negative (or
positive) influences.
D. A fourth objective of the study is to determine
critical parameters that can degrade SSD performance
and recommend ways to minimize such degradation.
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Section 3
Conclusions
This limited set of data seems to show several
important factors that can degrade the performance of
SSD systems. Occupant interaction with their mitigation
system can be a major determining factor whether the
EPA action level is achieved. One point that is very
evident from this durability diagnostics program is that
increases in radon levels can often be traced back to
occupant intervention with the SSD radon mitigation
system. Noise, whether electrical, vibrational, or aero-
dynamic, has been the primary reason that systems
have been turned off in all the areas of the country that
have been studied. Some systems are being turned off
when the occupants leave, even for a few days. Others
shut off the mitigation system when going away on
vacation. These last two reasons were given because
of a concern for the safety of the house, "we unplug our
refrigerator and other appliances when we leave, so
why not the radon system?" Still others have reported
the reasons for turning off the system were to conserve
energy or during periods of ventilating the house to "get
rid of the radon." Some of these people have forgotten
to turn the system back on for various periods of time.
At the time of the last durability testing in these
houses, all systems were operating satisfactorily. There
were no problems with the mitigation systems that were
installed properly and no complaints from the occu-
pants regarding these systems (Ref.5). Improper instal-
lation has caused problems by having the fan or fan
mount in solid contact with the structure of the house
that amplifies the vibrational noise to the point of an-
noyance to the occupant who then turns off the system.
Improper installation, where the slope of the pipe was
not sufficient to allow the condensation to drain back to
the subslab area, has created sloshing noises that
caused the occupant to turn off the system. This has
also completely blocked the pipe, effectively stopping
the operation of the system.
Fan failures (3 of 14: 2 capacitor, 1 bearing failure)
occurred within the first 90 days after installation in the
Piedmont Study houses. None have failed since, with
these systems operating for 2 to 3.5 years. The low
flow rates combined with the high temperatures and
moisture levels in the Florida mitigation systems ap-
pear to be causing fan motor bearing problems that
may lead to early failure (Ref. 6).
Fan motor capacitor failures have been reported by
another research group (Ref. 7), mitigators, and fan
manufacturers. Capacitors of a higher quality than those
that were originally installed on the fans are available,
but they are rated for 60,000 hours service or approxi-
mately 6.8 years. These capacitors may fail and cause
the fan motor either to run at a lower speed and
therefore be less efficient, or to stop running com-
pletely. It therefore is probably not reasonable to ex-
pect an active, fan operated radon mitigation system to
operate for the expected life of the building.
Grab samples of the radon levels in the SSD 'sys-
tem exhaust remained relatively constant over the test
period. Comparison between the New Jersey and
Florida houses shows that the amount of radon being
exhausted is roughly the same, though the flow rates in
the New Jersey SSD exhausts were higher by a factor
of 6 or more.
Long-term influences of the* SSD system operation
on the house substructure were evaluated and no quan-
titative results were obtained. Slab cracking was noted
only in House 3, and that could have been from normal
house settling (this was the newest house in the study
and was built on the side of a hill). Some subslab
areas of the houses were drier than when the mitiga-
tion was first installed. The occupants reported that it
was no longer necessary to use dehumidifiers in the
basements because they were less humid. Although
the mitigation system could be causing this phenom-
enon, climatic differences may be a contributor.
In summary, properly installed SSD systems ap-
pear to be maintaining the indoor radon levels at or
below the EPA action level of 4 pCi/L in all the New
Jersey houses tested. Modifications to the original
installations were necessary to reduce the indoor radon
level below 4 pCi/L, based on a post-mitigation radon
test. Once these modifications were accomplished, the
lower levels were maintained. Some Florida houses
were not reduced below the action level but remained
near the original mitigated levels as long as the sys-
tems were not turned off. The weather conditions
allowing for extended periods of window opening com-
plicate the analysis of the long-term alpha-track results.
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Section 4
Recommendations
1. Our number one recommendation would
be to test all mitigated houses at least
yearly, whether EPA R&D houses or
commercially mitigated, to determine
whether the mitigation system is controlling
the radon levels in the building. Many
systems will break down over time.
2. Mitigators should use long-service-life
components, such as heavy duty capacitors,
25 year rated sealants, quality mounting
hardware, and quality speed controls.
3. Installation practices should be improved.
An understanding of the system interaction
with other building components is essential.
Supporting the system with the fan could
load the fan in such a way that would
distort the housing and cause the impeller
to rub on the housing creating noise, and
causing early failure due to overheating.
These practices have to be part of the
training process for mitigators. Presently,
there are no prerequisites for trade skills to
become a mitigator, so they must be taught.
4. . Fan selection must be appropriate for the
installation. If a high flow is needed, then a
large enough fan should be installed.
Conversely, if low flows and higher
pressures are required, then the proper fan
should be selected.
5. Post-installation diagnostics should be
performed to make sure the system is
operating properly before the mitigator
leaves the house.
6. Alarm systems or performance indicators
should be installed on all active SSD
systems. Written instructions on how the
alarm or indicator works and what to do if a
failure occurs should be left with the
occupant for reference.
7. All systems should be marked as radon
mitigation systems so other craftspersons
will not do anything to jeopardize the
operation of the system.
8. Continue testing and evaluation of radon
mitigation systems until a statistically
significant number of systems have been
evaluated to produce solid performance
longevity estimates.
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Section 5
The Approach for Durability Testing
This approach to evaluation of durability is based
upon our own experience about what might happen
over time and also on the experiences of others; e.g.,
NYSERDA efforts to quantify durability (Ref. 8), LBL
research (Ref. 9), and Swedish studies that could look
at houses after 5 years of operation (Ref. 10). Five
data forms (Appendix A) have been developed that
serve two purposes. One purpose is to record the data
and the other is to serve as a check list for the investi-
gator. Form I emphasizes the history of the radon in
the house and mitigation system installation, modifica-
tion dates, and system operation as observed by the
house occupants. Form II lists pertinent house and
mitigation system characteristics. Forms III, IV, and V
involve a series of diagnostic tests that seek to deter-
mine whether the mitigation system is achieving the
necessary radon mitigation goals.
The following forms are used during the system
performance evaluation. The complete forms are pre-
sented in Appendix A.
A. Radon Durability Diagnostics -I The
Occupant Questionnaire
The first four questions are about the radon mea-
surements and mitigation system history.
Question 5, the most important question, is
whether the system has been running
steadily. Swedish studies have pointed to
the problem of systems not running steadily
as an explanation of increasing radon
concentrations (Ref. 10). Our own
experience is that occupants do not like to
admit shutting off the system, although
system noise, radio interference, and
conservation of electricity during the
summer or periods when the occupants
are away have been offered as reasons to
turn off the system.
Question 6 concerns noise perceived by
the occupant. If the system is becoming
noisy, our fear is that the fan may fail soon
or that noise may prompt occupants to shut
off the system.
Question 7 involves moisture. We are
seeking to gain insight into condensation,
collection of water in the mitigation piping,
or moisture-related events taking place at
the roof exhaust or along the piping inside
the house. Water in the piping can directly
influence the amount of exhaust airflow
possible. Condensation on the exterior of
the piping can be another cause for
occupants to turn off the mitigation system.
Question 8 is aimed at finding out about
possible power outages, construction in the
house, or other events that could account
for higher than expected radon levels.
Question 9 asks the occupant's perception
of the system and whether there are any
questions about the way it functions.
B. Radon Durability Diagnostics -II House
and Mitigation System Description
Data Form II is used to record basic house and
mitigation system design information. Heating/cooling
system type, house size, and soil contact area are
addressed. There are questions about the mitigation
system design and space foir a sketch of the system
layout.
C. Radon Durability Diagnostics -III Visual
Inspection
Form III is for recording the results of a visual
inspection of the mitigation system pipe connections
and mountings, electrical connections, condition of seal-
ing materials, and cracking of the walls or slab. Results
of the noise tests are also recorded here.
D. Radon Durability Diagnostics -IV
Diagnostic Measurements
Mitigation system pressure differences and flow
rates are entered on this form with exhaust radon
levels and pressure field extension data. The results of
testing the electrical performance of the mitigation fan
are noted in another section on this form.
E. Radon Durability Diagnostics -V Long-
term Radon Measurements
The pertinent data from the installation of the alpha
track radon detectors are recorded on this form. The
radon levels are entered on this form as they are
received from the laboratory.
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Section 6
Procedures
This section describes the procedures proposed
for the protocols. These procedures present methods
to determine the operating characteristics of a SSD
radon mitigation system to determine the durability of
operation of this system.
6.1 Pre-house Visit
Purpose: To reduce not-at-home incidences ,
and maximize field time usage.
6.1.1 Contact the "occupant of the house
before the visit to ensure that the house
will be in the "closed house" operating
condition for at least 24 hours before the
scheduled visit. ("Closed house" operating
condition means that all windows should
be closed, thermostat set for normal
temperature, and the mitigation system
operating.) Confirm appointment 24 hours
before visit.
6.1.2 Determine that ail measurement
equipment is functional: batteries charged,
probes functional, scintillation cells purged,
etc.
6.1.3 Have sufficient seals or sealing
materials available to temporarily and
permanently seal any holes that are drilled
in the mitigation system, slabs, or walls.
6.2 House Visit
6.2.1 Occupant Questionnaire (Form RDD-
Purpose: To obtain background radon and
mitigation system data.
6.2.2 Basic house and mitigation system
data (Form RDD-II). ,
Purpose: To obtain house size, heating/
cooling system, and mitigation system
design data.
6.2.3 Visual Inspection (Form RDD-III)
Purpose: To check condition of mitigation
system piping connections, electrical
connections, sealing materials, and
mounting hardware.
6.2.3.1 On the exterior of the house, inspect
the area of the mitigation system exhaust
for signs of moisture, staining, or blockage.
6.2.3.2 Inspect the slab(s) and basement,
crawlspace, or stub walls for signs of
cracking. Determine whether the cracking
is new, old, or an extension of previous
cracks. This can usually be ascertained by
the shade of coloring of the crack or by the
amount of interior dirt or debris that has
collected in the crack,
6.2.3.3 Inspect sealants used to seal cracks
or perimeter drains for integrity.
6.2.3.4 Inspect mitigation of slab or wall
joint for seal integrity.
6.2.3.5 Inspect mitigation system piping and
associated fittings for cracking or joint
failures.
6.2.3.6 Inspect mitigation system mountings
for security.
6.2.3.7 Inspect mitigation system electrical
connections for signs of damage such as
overheating, loose connections, or other
physical damage.
6.2.4 Mitigation System Pressure
Measurements (Form RDD-IV)
Purpose: To evaluate mitigation fan and
system performance.
6.2.4.1 If measurement holes are not
available in each branch of the mitigation
system, drill a hole in each branch large
enough to accommodate pressure and flow
probes (see flow measurements). After
drilling, seal temporarily with tape.
6.2.4.2 Make sure that the basement
windows and the basement/living space or
basement/outside door(s) are closed before
starting mitigation system pressure and flow
measurements. If these are open during
the measurements, wind and stack pressure
differences caused by these openings could
adversely affect these measurements.
6.2.4.3 Set up the pressure reading
instrument to measure difference (delta p)
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and connect the probe tubing to the "low"
pressure side of the instrument.
6.2.4.4 Insert the pressure probe into the
mitigation system exhaust piping
perpendicular to the flow stream and seal
the probe to the pipe to minimize
measurement errors.
6.2.4.5 Adjust the pressure measuring
instrument "zero" and select the proper
scale for this measurement. Read and
record the pressure difference. Recheck
the "zero" after each reading and make
corrections to the readings if necessary.
Repeat each measurement at least once.
Seal the hole in the pipe with tape after
removal of the probe.
6.2.4.6 Repeat the pressure measurements
in each branch of the mitigation system,
rechecking and adjusting the instrument
"zero" as necessary before and after each
reading.
6.2.4.7 Compare present readings with past
readings, if available, and note differences
on the form. Try to determine the cause of
the difference and record in the "Other
Observations" section of the form.
6.2.4.8 Remove the test probe from the
mitigation pipe and replace the temporary
seal.
6.2.5 Mitigation System Flow Measurements
(Form RDD-IV)
Purpose: To evaluate mitigation system fan
and system performance.
6.2.5.1 Make the mitigation system flow
measurements at the same points where
the pressure measurements were taken.
According to accepted measurement
practices, these holes should be drilled 7.5
pipe diameters downstream of fans, pipe
fittings, or other major changes in flow
direction or pipe size change, if possible
(Ref. 11).
6.2.5.2 Insert the velocity (flow) measuring
probe into the mitigation system exhaust
pipe to the centerline of the pipe, making
sure that the sensitive element of the probe
is in proper alignment with the flow stream,
per manufacturer's instructions. Seal the
probe to the pipe to minimize measurement
errors caused by leakage. Single point
measurement errors are not significant if
the flows are taken on the centerline of the
mitigation piping because flows above 90
ft/min are turbulent (Ref. 11).
6.2.5.3 Adjust the instrument "zero" before
and after each reading. Make adjustments
to the reading as necessary. Measure and
record the velocity (flow). Repeat each
measurement at least once.
6.2.5.4 Repeat the velocity (flow)
measurements in each branch of the
mitigation system, rechecking and adjusting
the instrument "zero" as necessary before
and after each reading. Make adjustments
to the readings as necessary.
6.2.5.5 Compare the present readings with
the past readings, if available, and note the
differences on the form. Try to determine
the cause of the difference and record in
the "Other Observations" section of the form.
6.2.5.6 Remove the test probe from the
mitigation pipe and replace the temporary
seal.
6.2.6 Mitigation System Exhaust Radon
Grab Samples (Form RDD-IV)
Purpose: To determine the amount of radon
being exhausted to the outside environment
and as a diagnostic to evaluate the effects
of cracking in walls or slabs. Lower
concentrations with increased flow rates in
the mitigation system suggest short
circuiting to ambient or inside air.
6.2.6.1 Radon grab samples can be made
through the same mitigation system test
hole that was used for the pressure and
flow measurements. This test should be
taken in the exhaust piping downstream of
all branches but upstream of the mitigation
system fan to prevent the discharge of
radon-rich soil gases .into the house during
testing. '
6.2.6.2 Insert the grab sample test probe to
the centerline of the mitigation pipe. Seal
the probe to the piping to reduce the errors
caused by air leakage into the mitigation
system. Make sure the filter is installed in
the probe line between the mitigation piping
and the scintillation cell.
6.2.6.3. Measure and record the scintillation
cell background counts for 5 minutes.
6.2.6.4 Connect the scintillation cell pump
system to the test probe and pump at least
10 cell volumes (Ref. 12) of mitigation
exhaust gas through the scintillation cell.
6.2.6.5 Disconnect the scintillation cell,
record the time the sample was taken, and
put cell aside for 15 minutes.
6.2.6.6 Repeat 6.2.6.3, .4, and .5 with
another scintillation cell. ,. •
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6.2.6.7 Fifteen minutes after taking the
radon grab sample, do a 2 minute count of
the activity in each cell that will give an
approximation of the exhaust radon levels.
6.2.6.8 Remove the test probe from the
mitigation pipe and replace the temporary
seal.
6.2.6.9 Count the scintillation cell activity
according to the EPA Indoor Radon and
Radon Decay Products Measurement
Protocols (Ref. 12) to determine the actual
exhaust gas radon level.
6.2.7 Pressure Field Extension
Measurements (Form RDD-IV)
Purpose: To evaluate mitigation system
performance and as a diagnostic to
determine blockage or short circuiting of
the subslab pressure field.
6.2.7.1 These measurements require that
holes be drilled through the slab into the
subslab area.
6.2.7.2 If pressure field extension is to be
measured, the mitigation system should be
in the normal operating mode. The lowest
inches of water range on some
micromanometers is more sensitive than
the pascal range and therefore would be
the range of choice on those instruments
(0.004 in. of water equals 1 Pa).
6.2.7.3 Measure and record the pressure
differential between the subslab and the
basement (room, crawlspace, etc.) for each
test point.
6.2-7.4 If zones of no pressure differences
are found, test to determine the cause for
the reduced pressure field extension. More
test holes must be drilled through the slab.
6.2.8 Mitigation System or Fan Noise
Detection [Form ROD -IV(2)]
Purpose: Early detection of fan motor or
bearing failure or other system noise.
6.2.8.1 Using a stethoscope, listen to the
fan operation by touching the disc-shaped
endpiece to the fan housing. Any high
pitched, grinding, or grating sounds should
be recorded on the forms and investigated
to determine if the fan bearings are failing.
6.2.8.2 Inspect the mounting of the fan and
adjacent mitigation system for proper
vibration isolation from the building structure.
If the system is contacting the structure
and/or resonating, remedial action should
be performed.
6.2.9 Mitigation System Fan Electrical
Performance [Form ROD -IV(2)]
Purpose: To determine status of electrical
performance of fan and components.
Capacitor failures can cause the fan to run
at lower than normal speed and therefore
not depressurize the subslab area enough
to maintain the indoor radon at an
acceptable level. A failed capacitor may
not allow the fan to start after the power
has been off.
6.2.9.1 Connect a pressure differential
instrument into the mitigation pipe and seal
the probe to the pipe to minimize
measurement errors.
6.2.9.2 Measure and record the pressure
difference. Turn off the fan and allow the
system pressure to drop to near ambient
level.
6.2.9.3 Turn the fan back on and observe
the pressure difference rise for about 2
minutes. If the system comes back to the
previous pressure difference, and that
pressure was within original installation
specifications, then the capacitor is good. If
the fan doesn't achieve operational speed
and the system pressure difference doesn't
rise to the prior level, then the capacitor is
suspect and should be replaced.
6.2.10 Installation and Removal of Long-
term Radon Detectors (Form ROD -V)
Purpose: To determine long-term indoor
radon levels.
6.2.10.1 Remove existing alpha-track
detectors, note date and time of removal
on the label and RRD:V. Note date and
time of installation on the new detector
label and on RDD-V.
6.2.11 Permanent Seal Placement (Form
ROD -V)
Purpose: To ensure that the testing does
not put the system operation in jeopardy in
the long-term.
Unless the house is ai research house that
is part of an on-going research program, all
temporary seals should be replaced with
permanent seals.
6.2.11.1 Sealing of test holes in the
mitigation piping can be accomplished by
using moldable epoxy to seal metal or
plastic chassis plugs into the holes.
6.2.11.2 Holes drilled into the slab or wall
should be plugged with an expanding type
of epoxy masonry cement to prevent
shrinkage cracking.
13
-------
6.2.12 Quality Assurance/Quality Control
The originals of all completed data forms,
records of phone conversations, or other
notes relevant to the program, and copies
of previous radon measurement or
mitigation records that the occupant may
possess, should be kept in a looseleaf
logbook that will be kept in the office. This
book should be subdivided into sections for
each house. Information such as the
originals of the alpha-track data from the
company that does the analysis also should
be kept in this logbook. Duplicates of the
above should be kept in another notebook
that can be designated for field use. This
procedure allows for safekeeping of the
records and provides a copy to be taken to
the field for comparison purposes or for
information feedback to the occupants.
14
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Section 7
Apparatus
This description of apparatus is general in nature.
Any equipment capable of performing the test mea-
surements within the allowable tolerances is permitted.
See Appendix B for a listing of typical measurement
instrumentation used in this practice.
Major Equipment
1. Pressure measuring instrumentation. A
micromanometer to measure pressure
differences with a range of 0.025 Pa to 5
kPa.
2. Velocity measuring instrumentation. An
anemometer or equivalent to measure
velocities with a range of 0.1 to 40 m/s.
3. Radon measuring instrumentation.
Scintillation cells and counting
instrumentation to measure radon levels
with a range of 37 to 370,000 Bq/m3.
Other Equipment and Supplies
1. Battery operated drill and drill bits.
2. Rotary hammer drill and masonry drill bits.
3. Tape measure.
4. Flashlight, spare batteries, and bulbs.
5. Clamp-on ammeter for AC current.
6. Stethoscope.
7. Vacuum cleaner and extension cord.
8. Duct tape.
9. Moldable epoxy.
10. Expandable epoxy masonry cement.
11. Mixing container and tools for applying
masonry cement.
12. Chassis plugs to seal holes in mitigation
piping.
15
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-------
Section 8
Results
8.1 Results from the New Jersey Piedmont
Houses
As previously discussed there are four objectives of
the study on which we must focus our attention. Per-
haps the easiest way to review the results is to plot the
radon levels measured over time for each Piedmont
houses. These houses were single family, free-stand-
ing houses located 40 miles north of Princeton, NJ.
Examples of these plots are shown in Figures 1 -8 and
summarized in Table 1.
Occupant Effects
Immediately evident in looking at Figures 1 and 2 is
that two houses (3 and 5) show major variations in
radon levels, while the majority of the houses show
more-or-less constant radon levels over time, Figures 3
and 4. These variations include radon concentrations
above the EPA action level as well as a return to pre-
mitigation levels for House 3.
The occupant of House 3 gave no hint on the
questionnaire that the SSD system wasn't working 100%
of the time. Only when we informed the occupant of
the return to pre-mitigation radon values did the occu-
pant remember that the system had been turned off
during a party when mitigation system noise was an-
noying and had not been turned back on for an ex-
tended period. We pursued this point further and dis-
covered that the noise was the result of physical con-
tact between the SSD fan and the second floor band
joist above the dining room in the attic above the
garage. This was an attached garage adjacent to the
dining room. This contact with the structural members
of the building creates a sounding-board effect that
amplifies the sound. A small modification to the mount-
ing eliminated the problem. Similar vibrational prob-
lems had also been experienced in one of our current
research houses. The annoyance of the vibration had
resulted in the system being turned Off. The impor-
tance of avoiding such problems should be empha-
sized with rnitigators.
Checking the occupant questionnaire it was noted
that the House 5 occupant had turned off the SSD
system because of radio interference and because it
was felt that, under mild weather conditions with open
basement windows, it was wasting energy to operate
the SSD system (Ref. 13). After listening to the radio
or ventilating the basement, the occupant would then
forget to turn on the mitigation system for long periods
of time. The result was that the integrated radon levels
for the test period were elevated.
One point was clear from even this very limited
number of test houses. The: SSD system cannot be
turned off for relatively short periods of time without
having an immediate impact on the radon level. The
one occupant explained that the system was turned off
only for radio weather broadcast to avoid the static.
The lesson is that the static sihould not be present if a
higher quality speed controller were used (when present
in the system) and carefully checking the wiring ar-
rangement to avoid interaction with sensitive electronic
equipment. Either airborne or AC noise carried over
the house wiring to the electronic equipment can be
the culprit. Once the occupants were shown the results
of their actions and the installation problems resolved,
the systems were left on and the radon returned to the
mitigated levels.
Seasonal Variability
To look for such effects as seasonal variability, we
must focus our attention on the houses where the
occupants have allowed the SSD systems to operate
100% of the time. Figures 3 and 4 show this type of
operation. If we do a very simple evaluation of events
over the measurement period using Table I data (the
basis for the figures) the stability of radon concentra-
tions over time can be demonstrated. In this exercise
we have averaged readings for the first two periods
and compared them to the last two measurement peri-
ods. Altogether 10 measurements can be compared if
all basement and crawlspace values are also aver-
aged. Thus comparing October 1987 through May
1988 to November 1988 through June 1989 (a similar
weather period) we find that in 7 out of 10 measure-
ments radon levels have dropped an average of 0.6
pCi/L. In 2 out of 10 houses, radon levels have in-
creased an average of 0.1 pCi/L and one value has
stayed the same. Since the alpha track method of
measuring radon levels has an error band that would
include these variations, our conclusion would be that
there is no significant change over this 1 year period.
Because of these same arguments of measure-
ment error, it is even more difficult to look for seasonal
effects. However, should there be any significant sea-
sonal influences they should be evident in these data.
House 2 (Figure 3) for example, shows that winter
readings are slightly higher than summer readings.
Again using October-February and November-March
17
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Table 1. Radon Concentrations In Eight Houses (pCl/L)
Hou*o No.
2
3
4
5
6
7
8
10
Location"
Basement
Basement
Dining Room
Basement
Basement
Living Room
Basement
Basement
Living Room
Breezeway
Basement
Bedroom
Basement
Basement
Crawlspace
Living Room
Basement
Crawlspace
Crawlspace
Living Room
Basement
Living Room
Basement
Family Room
Oct.' 87
Feb. '88
2.1
2.4
—
6.8
9.9
4.8
3.1
3.0
2.8
—
11.6
8.4
4.8
5.1
6.8
2.6
1.0
0.8
0.6
0.6
5.6
3.6
2.4
1.9
Feb. '88
May '88
1.9
1.3
—
1.1
1.2
0.6
2.3
2.6
3.1
—
0.7
0.8
1.9
2.5
2.8
1.6
0.3
0.6
0.3
0.3
1.9
1.7
2.2
1.9
May '88
Nov. '88
1.4
1:0
0.6
7.6
8.4
4.7
2.8
2.8
2.7
—
9.8
.. 6.0
1.7
2.3
2.2
1.3
0.5
0.2
0.4
0.3
0.9
1.1
1.8
1.7
Nov. '88
Mar. '89
1.8
1.1
1.5
53.2
40.6
27.0
2.6
—
i:s
2.1
12.9
12.4
2.7
2.2
—
1.8
1.2
1.1
0.8
0.3
3.6
4.4
2.6
2.7
Mar. '89
Jun. '89
1.3
1.1
0.4
2.5
3.6
0.8
—
—
1.0
1.3
0.4
0.6
3.1
2.4
—
1.8
0.5
0.3
—
0.3
2.2
0.9
1.5
1.3
* Multiple basement or crawlspace readings are from duplicate sensors placed 30 cm apart
Durability-House 3
i r
Oct-Feb Feb-May May-Nov Nov-Mar
Month (1987-1989)
Mar-Jun
Jun-Nov
-«- Basement -»- Basement
• Dining Room
Figure 1. Radon Levels in House 3.
18
-------
basement values we are seeing a 1.6 pCi/L average
versus 1.2 pCi/L for May-November combined with
March-June. This 0.4 pCi/L difference is well within the
error band.
House 4 (Figure 5) shows a general decline
in radon concentrations with time and no
sign of seasonal fluctuations.
House 6 (Figure 6) shows a very slight
increase in the November-June reading and
a noticeable drop in radon concentrations
follows the October 87-February 88 period.
One explanation for this could be because
standing water beneath the slab was no
longer present after February. This could
allow for better pressure field extension and
therefore lower radon.
House 7 (Figure 4) also shows a very small
increase in the November-June period in
basement and crawlspace radon
concentrations. First floor concentrations
are background levels. Note that the
substructure concentration change is from
approximately 0.5 to 1.0 pCi/L, again well
within the error band of the alpha track
radon sensors.
We see variations in the November 88-March 89
period that could only be viewed as seasonal influ-
ences in Houses 8 and 10. In the case of House 8
similar increased concentrations were measured during
the October 87-February 88 period. Averaging the val-
ues for House 8 (from Table 1) for the "winter periods"
we have averages of 4.6 pCi/L for the basement and
4.0 pCi/L for the living room, a value at or above the
EPA action level. If we average "spring, summer, and
fall periods" the average value is only 1.7 pCi/L in the
basement and 1.2 in the living room. This house illus-
trates how seasonal influences can bias SSD perfor-
mance results. The annual average is still below the
EPA action level of 4 pCi/L.
House 10 shows only a slight increase in
radon concentration in the October 87-
February 88 period; i.e., 2.2 pCi/L average
14-
Durability House 5
12-
10-
8-
6-
4 —
2-
1
Feb-May
Oct-Feb
May-Nov Nov-Mar
Month (1987-1989) ,
Mar-Jun
Jun-Nov
-N- Basement
• Bedroom
Figure 2. Radon Levels in House 5.
19
-------
12-
10-
8-
6-
4-
Oct-Feb
Figure 3. Radon Levels In House 2.
Durability - House 2 •.
Feb-May
May-Nov
Month (1987-1989)
Nov-Mar
• Basement , -e- Basement -»- Dining Room
Mar-Jun
S.
12-
10-
8-
6-
4-
2-
Durability-House 7
Oct-Feb Feb-May
May-Nov Nov-Mar
Month (1987-1989)
Basement -a- Crawlspace 1 -»- Crawlspace 2
Mar-Jun
, Living Room
Jun-Nov
Flguro 4. Radon levels In House 7.
20
-------
12-
Durability - House 4
10-
8-
o
Oct-Feb
Feb-May
May-Nov
Month (1987-1989)
Nov-Mar
Mar-Jun
Basement -a- Basement -«- Living Room -*- Breezeway
Figure 5. Radon levels in House 4.
Durability - House 6
Oct-Feb
Figure 6. Radon Bevels in House 6.
Feb-May
May-Nov
Month (1987-1989)
Nov-Mar
Mar-Jun
• Basement -e- Basement -*- Crawlspace -«- Living Room
21
-------
Durability - House 8
(9
BC
0
Oct-Feb
Feb-May May-Nov Nov-Mar
Month (1987-1989)
-*- Basement -e- Living Room
Mar-Jun
Jun-Nov
Figure 7. Radon levels In House 8.
•8
CO
CC
12-
10-
8-
6-
4-
Oct-Feb
Durability - House 10
Feb-May May-Nov
Month (1987-1989)
-*- Basement -e- Family Room
Nov-Mar
Mar-Jun
Figures. Radon levels In House 10.
22
-------
versus 1.5 pCi/L for the "summer periods".
However, the increase is more substantial
in the November 88-March 89 period when
values of 2.7 pCi/L are observed. This
house also would appear to exhibit seasonal
effects that increase the radon
concentrations, but only by about 1 pCi/L
Radon Levels In the Mitigation Exhaust
System
One measurement of the durability testing that is of
interest is the concentration of radon in the exhaust
pipe from the subslab mitigation system. When this
information is combined with the flow measurement at
the same pipe location, we can calculate the total flow
of radon from the mitigation system (Ref. 14).
One question to be resolved is: Can we compare
the amount of radon exhausted from any given house
and understand fully the role played by the mitigation
system? In the absence of a mitigation system, the
natural flow of radon through the house would be the
airflow rate (i.e., the average air infiltration rate, Alav )
of the house times the indoor radon concentration. To
make the calculation of the natural flow requires a
knowledge of the average air infiltration rate for the
house, the radon concentration upstairs and in the
basement/crawlspace, as well as the volumes of those
zones. The calculation proceeds as follows:
R = Al 103
• V J
where R - the radon flow, pCi/h
Al - air infiltration, m3/h
C - radon concentration, pCi/L
V - volume, m3
u - upstairs, and
b/c- basement/crawlspace
Results of this type of simple analysis for five Pied-
mont houses are shown in Table 2. The ratio of radon
being exhausted from each house by the mitigation
system to the natural radon flow through the house in
the unmitigated state varies from 1 to 9 for these
Piedmont study houses. The ratio of these two flow
rates could provide a preliminary measure of the addi-
tional subsoil radon drawn out of the soil and released
to the ambient air as a result of installing the SSD
mitigation system. The subslab and surrounding soil
conditions play an important role in determining the
amount of radon entry into the house or available to the
mitigation system.
For instance, House 4 is built on low porosity soil,
wet clay, and has a natural radon flow rate comparable
to the other houses, 7.5 ± 3 x 106 pCi/h, except House
3. House 4 is a house where high ventilation rates,
such as using a blower door to exhaust the house air,
depress the radon levels and then it takes many hours
for the house to return to the previous elevated levels.
Such behavior has been interpreted as evidence of a
limited radon entry rate. House 3 was built on high
porosity soil (i.e., stone flour roughly 0.3 cm in diameter
and has a good gravel bed beneath the slab, just the
opposite conditions of House 4) and has a natural flow
rate of 35 x106pCi/h. .
Once the mitigation system is turned on, the ability
of the system to communicate with the surrounding soil
is demonstrated. The total amount of radon mechani-
cally exhausted from the soil varies by a factor of 7 in
these houses. The lowest value is for House 4 with the
clay soil, and is the same as the natural flow through
the house. The highest value is for House 3 with the
very porous soil. In other houses, such as 5 and 7, the
"mining" of radon is demonstrated by the ratio of mitiga-
tion exhaust flow to natural flow, ratios of 9 and 8,
respectively. Both houses were built on soils of a clay/
Shale mixture. House 2 is located on clay/shale soil
also, but has a relatively high water table, approxi-
mately 1.5-2 m.
The method used to analyze the radon concentra-
tions from the mitigation system exhaust involves the
use of scintillation cells to take grab samples. Analysis
of the scintillation cells takes into account the time
elapsed .from when the sample was taken to when it
was analyzed, the background level of the cell, and the
efficiency of the measurement equipment.
Several other points should be noted. Taking a 2-
minute count, about 15 minutes after taking the sample,
which requires bringing the radon measuring instru-
mentation to the field, provides a direct count reading
that is roughly equal to that of the final corrected read-
ing (i.e., ± 25%). This is useful when checking radon
levels. The grab or pumped samples require the use of
filters to avoid ingesting progeny that will invalidate the
reading.
Data collection on the radon exhaust concentra-
tions from the Piedmont houses involved both pumped
and grab samples. Data are listed in Table 3. The
pumped samples generally produced higher readings
than the evacuated grab samples. This could be due to
different factors, but the most probable explanations
are that either not enough vacuum was pulled on the
cel|s or there was slight leakage in one of the fittings.
For these reasons, we would recommend taking
grab samples by the pump-through method rather
than using evacuated cells.
Based on the pumped samples, the first 4-month
period the majority of the measurements showed that
the radon concentrations were reduced. In the second
and third testing periods (6/89 and 11/89) the concen-
trations vary with the individual houses. Houses 3 and
10 (Figures 1 and 8) show a decreasing trend while
Houses 2, 4, 5; 7, and 8 indicate increasing radon
concentrations. Some seasonal effects may be present
23
-------
Table 2. Comparison of Radon Quantities Exhausted by Mitigation Sytems and by Natural Means Based on Five Houses
Hou»o Rn Level (pCI/L)
No. Basement Upstairs
2 22
3 170
4 29
5 60
7 33
15
70
56
35
18
House Volume (m3) Al v
Basement Upstairs (mf/R)
219
224
211
371
199
296
469
499
398
392
398
338
283
135
203
Rn Level
Exhaust
(pCi/L)
154
946
44
435
504
Exhaust Rn Quantity (pCi/h) Ratio: Mitlga-
Flow Exhaust Natural tlon/Natural
(m3/h)
102
76
246
132
76
15,731,000
\ 73,167,000
10,902,000
57,767,000
38,687,000
6,974,000
34,585,000
10,478,000
6,353,000
4,680,000
2.26
2.12
1.04.
9.09
8.27
In that the lowest readings for the majority of the houses
were In March and June of 1989, which is the warmer
time of the year.
Throughout these discussions, radon concentration
has been used, to provide the more physical meaning,
and because airflow rates (necessary to provide total
radon flow as shown in Table 2) tend to be constant in
the houses. One exception to constant flow is House 3
where, after the fan had been turned off by the occu-
pant, and after radon levels had increased in the living
space, the fan speed was increased. Duct flows
changed from 21.4 L/s in November 1988 to 66.5 L/s in
November 1989 (intermediate readings were 58.4 Us).
The trend of falling concentration levels over time for
House 3 continued to the end of the testing in Novem-
ber 1989. The profile of House 3 is opposite to the
general trend experienced in most of the test houses.
This higher flow rate combined with lower exhaust
radon levels is indicative of short circuiting of the SSD
to either ambient air or basement air. Cracking of the
slab was noted in House 3 and is discussed in the next
section.
Substructure Changes
Based upon diagnostic team observation, only
House 3 showed evidence of physical changes. Two
cracks appeared in the basement slab near the slab
edge extending toward the center of the room. Length
of the cracks was approximately 6 ft and the width
exceeded 1/16 in. at some locations. Flow from the
basement into the subslab area through these cracks
was determined with the use of a smoke tracer.
A noteworthy observation was that .conditions were
noticeably drier in the basements and/or beneath the
slab in some of these houses. Several occupants have
stated that the need for summer dehumidification was
eliminated in their houses. Where observations were
possible, Houses 2,4, and 6, water in gravel beds was
no longer visible. No quantitative measurements of
relative humidity have been made.
8.2 Results from the NJDEP Houses
These houses were mitigated by professionals hired
by the owners directly, with no input from anyone from
the research community.
The concern for durability and performance of ra-
don mitigation systems was pointed out by DePierro
and Cahill of the NJDEP (Ref. 15). , Based upon their
findings 64% of the houses mitigated by owners and
professional mitigators were not achieving the 4 pCi/L
action level. When only professionally mitigated houses
were assessed the percentage of houses failing to
meet the action level still exceeded 50%.
With this information as background we undertook
a program of upgrading the radon information. The list
of our test houses was taken from the larger list of
houses tested by NJDEP. From that list our criteria of
selection were houses less than 1.5 hours drive from
Princeton, houses with SSD systems installed as the
major mitigation system, and houses with the highest
post-mitigation radon levels. Our approach was to
question the occupant on the radon history in their
house, to inspect the mitigation system installation, and
to leave a charcoal canister in the house that the
occupant would mail to NJDEP for analysis after 3 days
of exposure.
Test house A. This house has a SSD
system, that uses two basement slab and
one crawlspace slab penetrations routed to
a fan mounted on a crawlspace cinder block
wall. Noise from the fan caused the owner
to build an insulated box around the fan.
Radon levels measured in the house in
early 1987 were from 40 to 120 pCi/L in the
basement and 13 to 15 pCi/L upstairs. The
test results received from state and the
private mitigator did not agree.
Measurements 1 year later, after mitigation,
showed levels reduced to less than the
EPA action level. Our measurements in
October 1989 confirmed that the action level
was being met.
Test house G. The SSD system in this
house has one basement sump, one
basement slab, and one crawlspace slab
24
-------
penetrations as well as a penetration at the
wall adjacent to the crawlspace. Early
readings in September 1987 were 143 pCi/
L in the basement and 75 pCi/L in the living
room. Levels dropped to only 6 to 7 pCi/L
in the basement and living room until an
improved fan, Kanalflakt K-6, replaced the
original fan and dropped levels to the 0.8
pCi/L level. Our tests in August 1989
showed minimum detectable concentrations
of 0.54 pCi/L.
Test house J. In this house the SSD system
penetrated the basement floor at the sump
hole and a wall adjacent to a slab-on-grade.
Initial readings (3/87) were 260 pCi/L in the
small windowless basement and 23 pCi/L
in the family room above. After mitigation
(6/87) basement levels dropped to 12.7
pCi/L and bedroom and family room
measurements were less than 2 pCi/L. Our
August 1989 readings showed that the
basement radon level was 1.8 pCj/L.
Test house C. This house used a passive
ventilation approach to radon mitigation,
adding additional crawlspace vents to
provide cross flow of outside air in the
affected crawlspace. Early readings in 1987
were 8 pCi/L. The readings in August
1989 showed only a minimum detectable
concentration of 0.34 pCi/L.
To review these data briefly, we found no cases
where the substructure radon levels were above the 4
pCi/L action level. This was true though we chose the
highest radon houses on the list supplied by NJDEP.
One reason for this was that owners continued to have
the radon levels measured and had their systems im-
proved with better fans that provided higher SSD flow
rates. Fan lifetime appears to be short in certain of the
fans used, while the in-line centrifugal fans continued to
perform satisfactorily. Similar to the Piedmont houses
and our other test houses, noisy fans can be a result of
improper fan mounting. Good installation practices are
essential if this critical problem is to be avoided.
8.3 Durability Data from Other Research
Groups
Three other research groups, Southern Research
Institute, Oak Ridge National Laboratory, and Univer-
sity of Florida, are also working on the documentation
of SSD durability. All three groups were supplied with
an earlier version of the forms we developed and a
brief text explaining the goals. In this section we will
discuss the information received from ORNL and from
SRI. At the time of this report writing, the University of
Florida had not completed their study.
Oak Ridge National Laboratory, ORNL
The ORNL group supplied a series of house de-
scriptions of test houses in Tennessee. Although they
did not use the durability forms developed during this
program, some information relevant to the durability of
the mitigation systems was included.
The data from ORNL House 13 suggests that pres-
sures under the slab were relatively steady but radon
levels decreased over time in some slab test holes,
varied over time in others, and increased over time in
still others.
Similar data are found for ORNL House 14 where
randomness in the radon levels was exhibited. For
these houses, and the other house data supplied by
the ORNL research team, emphasis was on conditions
in the pits and holes beneath the slab and not on the
substructure, interior conditions, or the occupant re-
sponses.
Southern Research Institute, SRI
SRI supplied durability information in the form of an
earlier version of the durability diagnostic forms filled
out for their test houses B-2, B-3, and B-11. Houses B-
3 and B-11 experienced fan noise problems, causing
the fans to be turned off. Some noise was described
as a "high-pitched whine — possibly a bearing." The
mitigation system fan in B-3 failed and had to be re-
placed in November 1988.
All three houses had condensation in the mitigation
pipes, with B-3 being the worst a few days after instal-
lation. Although the moisture is evident at each inspec-
tion, it doesn't seem to be affecting the fan flow.
Followup durability testing in B-11 indicates that the
mitigation system flows and pressures are remaining
relatively constant. From 2/88 to 11/88 the interior ra-
don levels were steady at 4.5 pCi/L. The mitigation
system was turned off from 12/88 to 5/89 because of
the fan noise and the radon level averaged 13 pCi/L.
From 5/89 to 8/89 the radon level averaged 5.9 pCi/L
with the fan allegedly on all the time.
The radon levels in B-3 were found to vary in a
range from 4 to 7 pCi/L (the exception was an alpha
track reading of 1.4 pCi/L with a duplicate detector at
7.3 pCi/L) over a period of more than a year. Only one
durability test was completed on this house at this
time.
The radon levels, after mitigation, in House B-2
started at 15 pCi/L, rose to 89 pCi/L when the mitiga-
tion system was off for the entire period, then was
reported to be 10 pCi/L during a 3 month period when
the house was closed. There were also 3 month alpha
track readings of 3 and 7.5 pCi/L that correlated with
lengthy periods of the house being open. Further com-
plicating the analysis of the durability data is that the
occupants typically turn off the electricity if they are
going to be away for a few days. The mitigation system
suction pressures were the same for two measurement
periods. The exhaust flow for the second period and
the subslab pressure differentials for the first period
could not be measured because of gusty wind condi-
tions.
25
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Exhaust radon concentrations are noted as 4700
pCl/L for B-3 with a flow rate of 3 L/s for an hourly
exhaust rate of 52.4 x 106 pCi. B-11 with an exhaust
concentration of 3500 pCi/L and a flow rate of 2.8 Us,
single suction pit, in February 1988, results in hourly
radon exhaust flow of 36 x 106 pCi. The reported
exhaust rate in January 1990 was 44 x 106 pCi/h with
the system flow rate at 8.3 L/s, and two suction pits
operating. Thus with a flow rate increase of a factor of
3, there was only a 20% increase in radon being ex-
hausted from House B-11.
These mitigation system exhaust radon concentra-
tions were noticeably higher than those in the Piedmont
study houses, which were in the 50 to 1000 pCi/L
range. However, the flow rates in B-3 and B-11 were
only 2.8 and 8.3 L/s, respectively, compared to 19 - 66
L/s in the Piedmont houses. Thus, the actual radon
quantities being exhausted from these Florida SSD
systems are within the range of levels measured in the
Piedmont houses.
8.4 QA/QC Statement
Results from NJ Piedmont Houses
As presented in Section 6, Procedures, all mea-
surements that were performed on the NJ Piedmont
Study houses were in accordance with existing stan-
dards. These measurements, except the alpha-track
detectors, met the data quality goals set forth in the
QAPP for this study. Duplicate alpha-track detectors
mounted 30 cm apart sometimes gave results that
exceeded the accuracy limits set forth in the QAPP.
Results from NJDEP Houses
The radon measurements supplied to Princeton
researchers by the house occupants were provided by
commercial radon testing companies. The accuracy of
these data is probably not as good as the Princeton
data because some of these measurements were made
before the EPA Radon Measurement Proficiency (RMP)
program was started. The NJDEP radon measurements
were assumed to be more reliable because their facility
had tighter QA/QC.
Results from other Research Groups
These data were gathered in accordance with their
particular QAPP and met those requirements.
26
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Section 9
References
1. ASTM E 631 Terminology of Building Constructions,
1987.
2. Dudney, C.S., et al., Investigation of Radon Entry
and Effectiveness of Mitigation Measures in Seven
Houses in New Jersey, EPA-600/7-90-016 (NTIS
DE89016676), August 1990.
3. Harrje, D.T. and Hubbard, L.M., Proceedings of
the radon diagnostics workshop, April 13-14,1987.
EPA-600/9-89-057 (NTIS PB89-207898) June 1989.
4. Harrje, D.T., Hubbard, L.M., and Sanchez, D.C.,
Diagnostic approaches to better solutions of radon
IAQ problems, Healthy Buildings '88 - Planning,
Physics and Climate Technology for Healthier
Buildings, Vol. 2, Swedish Council for Building
Research, Stockholm, Sweden, 020:1988, pp. 143-
152.
5. Gadsby, K.J. and Harrje, D.T., "Durability of Subslab
Depressurization Radon Mitigation System
Performance," Proceedings: The Fifth International
Conference on Indoor Air Quality and Climate, Vol.3,
pp 445-450, Toronto, Canada, 1990.
6. Southern Research Institute durability forms, 1990.
7. Scott, A.G. and Robertson, A., "Long-term
Performance and Durability of Active Radon
Mitigation Systems in Eastern Pennsylvania
Houses," Presented at the 1990 International
Symposium on Radon and Radon Reduction
Technology, Atlanta, GA. February 19-23,1990.
8. Nitschke, I., Clarkin, M., Brennan, T., Rizzuto, J.,
and Osborne, M., "Preliminary Results from the
New York State Radon-Reduction Demonstration
Program," Proceedings: The 1988 Symposium on
Radon and Radon Reduction Technology, Vol.1,
EPA-600/9-89-006a (NTIS PB89-167480), 1989, p.
/"lO*
9. Prill R.J., Fisk, W.J., and Turk, B.H., "Monitoring
and Evaluation of Radon Mitigation Systems Over
a Two-Year Period," Proceedings: The 1988
Symposium on Radon and Radon Reduction
Technology, Vol.1, EPA-600/9-89-006a (NTIS PB89-
167480), 1989, p. 7-93.
10. Nilsspn, I. and Sandberg, P.I., Radon in Residential
Buildings - Examples of Different Types of Structural
Counter-Measures, Healthy Buildings '88, Vol. 2,
Planning, Physics and Climate Technology for
Healthier Buildings, Swedish Council for Building
Research, D.20: Stockholm, Sweden, 1988, pp.
163-172.
11. ASHRAE Fundamentals, 1990.
12. Indoor Radon and Radon Decay Product
Measurement Protocols, U.S. EPA, Office of
Radiation Programs, February 1989.
13. Harrje, D.T., and Gadsby, K.J., "Airflow
Measurement Techniques Applied to Radon
Mitigation Problems." Proceedings of the 10th AIVC
Conference - Progress and Trends in Air Infiltration
and Ventilation Research, AIVC, Coventry, UK,
1989.
14. Harrje, D.T., Hubbard, L.M.a Gadsby, K.J., Bolker,
B., and Bohac, D.L., 'The Effect of Radon Mitigation
Systems on Ventilation in Buildings," ASHRAE
Transactions 1989, Vol. 95, Pt. 1.
15. DePierro, N. and Cahill, M., "Radon Reduction
Efforts in New Jersey," Proceedings: The 1988
Symposium on Radon and Radon Reduction
Technology, Vol.1, EPA-600/9-89-006a (NTIS PB89-
167480), 1989, p.7-1.
27
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Section 10
Appendices
Appendix A. Radon Durability Diagnostics
Forms
The following five radon diagnostics forms are used
during the SSD durability testing. Not all sections of
every form are applicable to each individual house and
some conditions may require using the open spaces or
backs of the forms to record observations. They were
designed to provide a check list and a logical sequence
to gather information efficiently.
29
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RDD-I
RADON DURABILITY DIAGNOSTICS -I
Occupant Questionnaire
House ID
Date
1. Radon History
First observation:
Test Location LeveKpCiTL)
Test Method
Test Co. Name
2. Mitigation System Installation
Type
Cost
Company Name
3. Follow-up Test Results
Date Test Location Level(pCi/L)
Test Method Test Co. Name
4. Have there been any modifications to the original mitigation system, including replacement
of the fan or other components ? Y[ ] N[ ]
Date Type Cost Company Name
5. Has the mitigation system been nm-ning continuously during these past months? Y[ ] N[ ]
If not, what period(s) has it been off? . Why was it turned off?
6. Has there been any noise when the mitigation system operates? Y[ ] N[ ]
If yes, describe the noise and when the noise occurs?
30
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RDD -1(2)
RADON DURABILITY DIAGNOSTICS -1(2)
7. Has there been any moisture present along the mitigation system piping or at the point of
exhaust? Y[ ] N[ ]
If yes, describe problems:.
8, Have there been any events in or near the house that may have influenced the radon
mitigation system operation? (construction, major power outage, etc.) Y[ ] N[ ]
If yes, describe: ,. ^
9. Are there any features of the mitigation system you have questions about?
31
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House ID
Address
House Style_
RDD-II
RADON DURABnJTY DIAGNOSTICS -II
House and Mitigation System Description
Heating System Type
Air Handlers) Location(s)_
Mitigation System Description:
Date
Inspector
Organization
Substructure
Footprint sqft
Central Air Y[ ] N[ ]
Mitigation System Exhaust Location:,
Fan Mfg..
Fan Model No. _
Sketch of Mitigation System and Slab Plan (with test point locations noted)
32
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RDD-III
RADON DURABILITY DIAGNOSTICS -in
Visual Inspection
House ID
Date
1. Are there any signs of moisture or staining in the area of the mitigation system exhaust?
Y[ ] N[ ]. Is the system exhaust blocked? Y[ ] N[ ] If yes, explain._
2. Inspect the basement (crawlspace, room) slab and walls for new or expanded cracking. Note
condition. -
3. Inspect the condition of sealants used to seal cracks and/or perimeter drains. Note condition.
4. Inspect mitigation pipe to slab or wall joint for integrity. Note condition.,.
5. Inspect mitigation system piping and associated joints for cracking or joint failures.
Note condition. '
6. Inspect mitigation system mountings for security. Note condition.
7. Inspect mitigation system electrical connections for signs of damage; such as overheating,
loose connections, or other physical damage. Note condition.
33
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RDD-IV
RADON DURABILITY DIAGNOSTICS -IV
Diagnostic Measurements
House ID.
Date
Mitigation System Pressure and Flow Measurements
1. Measure pressure differentials in mitigation system piping. Check and adjust zero before & after each reading. Make correction
to the readings if necessary. Basement windows and doors should be closed.
Location
sent
Previous (change +)
1).
2).
3).
2. Measure the airflow in the mitigation system piping. Check and adjust zero before & after each reading. Make corrections to thj
readings if necessary. Basement windows and doors should be closed.
Location
ient
Previous (change +.)
1).
2)
3)
Mitigation System Exhaust Radon Grab Samples
1. Assemble radon grab sample probe with filter, install into pipe, and seal. After taking background counts, attach cell to prot
assembly and pump at least 3 cell volumes of exhaust air through the cell.
First cell Second Cell
Scintillation cell no.
Background (10 min.)
Time collected
Time analyzed (> 15 min.)
Total count (2 min.)
Approx. radon cone.
Time analyzed (>4 hr)
Counts/min
Radon cone.
34
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RDD-IV(2)
House ID
Radon Durability Diagnostics -IV(2)
Date
Pressure Field Extension Measurements
1. Determine that the mitigation system is in the normal operating mode. Basement windows
and doors should be closed. Check and adjust instrument zero before and after each measurement
point.
Test point
number
Distance from
suction point
Reference
point press.
Mitigation
suction press.
Mitigation System or Fan Noise Detection
Fan or motor noise? [Y] [N] Vibrational or aerodynamic noise [Y] [N]
Describe:
Mitigation System Fan Electrical Performance
Before pressure After pressure
Pan operation satisfactory? [Y] [N] If not, explain.
Other Observations:
35
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RDD -V
House ID
Alpha track
sensor location
1)
2)
3)
4)
RADON DURABILITY DIAGNOSTICS -V
Long-Term Radon Measurements
Date
Previous
sensor no.
Radon
level
Time
changed
New
sensor no.
Seal Replacement
Mitigation pipe test holes sealed? [Y] [N]
Slab and wall test holes sealed? [Y] [N]
Remarks
36
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Appendix 13. Measurement Equipment
Used in This Study
1. Neotronics model EDM-1 Electronic Digital
Micromanometer
Ranges:
0.001 to 19.99 in. WC
1.0 to 5000 Pa
2. Dwyer pitot tube model 166-6
3. Solomat MPM 2000 with Modumeter 2013
and Model 129MS anemometer probe
Ranges:
0 to 3000 ft/min
0.01 to 15.0 m/s
4. Pylon AB-5 Portable Radiation Monitor with:
LCA-2 Lucas cell adapter
Model 110 scintillation cells
37
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Glossary
See definitions ASTME 631 (Ref.1)
Air changes per hour (ach) - The number of times
within 1 hour that the volume of air inside a house
would nominally be replaced, given the rate at which
outdoor air is infiltrating the house. If a house has 1
ach, it means that all the air in the house will be
nominally replaced in a 1-hour period.
A|r infiltration rate - The rate at which the house air
is replaced with outdoor air. Commonly expressed in
terms of m3/h or air changes per hour.
Basement - A type of house construction where the
bottom level has a slab (or earthen floor) that averages
3 ft or more below grade level on one or more sides of
the house and is sufficiently high to stand in.
Block wall -A wall constructed using hollow rectangu-
lar masonry blocks. The blocks might be fabricated
using a concrete base (concrete block), using ash
from combustion of solid fuels (cinder block), or ex-
panded clays. Walls constructed using hollow blocks
form an interconnected network with their interior
hollow cavities unless the cavities are filled with con-
crete.
Crawlspace - An area beneath the living space in
some houses, where the floor of the lowest living area
is elevated above grade level. This space (which
generally provides only enough head room for a
person to crawl in) is not living space, but often
contains utilities. Distinguished from slab-on-grade or
basement construction.
Cubic feet per minute (cfm) - A measure of the
volume of a fluid flowing within a fixed period.
Depressurization - In houses, a condition that exists
when the air pressure inside the house or in the soil is
less than the air pressure outside. The lower levels of
houses are usually depressurized during cold weather,
due to the buoyant force of the warm indoor air
(creating the natural thermal stack effect). Houses
also can be depressurized by winds and by appliances
that exhaust indoor air.
Detached houses - Single family dwellings as op-
posed to apartments, duplexes, townhouses, or con-
dominiums. Those dwellings that are typically occu-
pied by one family unit and that do not share founda-
tions and/or walls with other family dwellings.
Entry routes - Pathways by which soil gas can flow
into a house. Openings through the flooring and walls
where the house contacts the soil.
Exfiltration - The movement of indoor air out of the
house. The opposite of infiltration.
Exhaust fan - A fan oriented so that it blows indoor air
out of the house. Exhaust fans cause outdoor air (and
soil gas) to infiltrate at other locations in the house, to
compensate for the exhausted air.
French drain (also perimeter drain, channel drain,
or floating slab) - A water drainage technique in-
stalled in basements of some houses during initial
construction. If present, typically has a 1 - or 2-in. gap
between the basement wall and the concrete floor slab
around the entire perimeter inside the basement to
allow water to drain to aggregate under the slab and
then soak away.
Grab sample - A sample of air or soil gas collected in
an airtight container for later measurements of radon
concentration.
Grade (above or below) - The! term by which the level
of the ground surrounding a house is known. In
construction typically refers to the surface of the
ground. Things can be atgrade, belowgrade, orabove
grade relative to the surface of the ground.
House air - Synonymous with indoor air. The air that
occupies the space within the interior of a house.
Indoor air - The air that occupies the space within the
interior of a house or other building.
Infiltration - The movement of outdoor air or soil gas
into a house. The infiltration that occurs when all doors
and windows are closed is referred to in this document
39
-------
Glossary (cont)
as the natural closed-house infiltration. The reverse of
exfiltration.
Joist - Any of the parallel horizontal beams set from
wall to wall to support the floor or ceiling.
MHlgator - A professional who works for profit to
correct radon problems. A person experienced in
radon remediation. At present, training programs are
underway to provide working professionals with the
knowledge and experience necessary to control ra-
don exposure problems. Some State radiological
health offices have lists of certified professionals.
Permeability (sub-slab) - A measure of the ease with
which soil gas and air can flow through a porous
medium. High permeability facilitates gas movement
under the slab, and therefore generally simplifies the
implementation of sub-slab suction.
PIcocurle (pCI) - A unit of measurement of radioactiv-
ity. A curie is the amount of any radionuclide that
undergoes exactly 3.7 x 1010 radioactive disintegra-
tions per second. A picocurie is one trillionth (10"12) of
a curie, or 0.037 disintegrations per second.
PIcocurle per liter (pCI/L) - A common unit of mea-
surement of the concentration of radioactivity in af luid.
A picocurie per liter corresponds to 0.037 radioactive
disintegrations per second in every liter of air.
Pressure field extension - A spatial extension of a
variation in pressure as occurs under a slab when a
fan ventilates at one or a few distinct points.
Radon -The only naturally occurring radioactive ele-
ment that is a gas. Technically, the term "radon" can
refer to any of several radioactive isotopes having
atomic number86. In this document, the term is used
to refer specifically to the'isotope radon-222, the
primary isotope present inside houses. Radon-222 is
directly created by the decay of radium-226, and has
a half-life of 3.82 days. Chemical symbol Rn-222.
Radon progeny - The four radioactive elements that
immediately follow radon-222 in the decay chain.
These elements are polonium-218, lead-214, bis-
muth-214, and polonium-214. These elements have
such short half-lives that they exist only in the pres-
ence of radon. The progeny are ultrafine solids that
tend to adhere to other solids, including dust particles
in the air and solid surfaces in a room. They adhere to
lung tissue when inhaled and bombard the tissue with
alpha particles, thus creating the health risk associ-
ated with radon. Also referred to as radon daughters
and radon decay products.
Slab - A layer of concrete, typically about 4 in. thick,
which commonly serves as the floor of any part of a
house whenever the floor is in direct contact with the
underlying soil.
Slab-below-grade - A type of house construction
where the bottom floor is a slab that averages between
1 and about 3 ft below grade level on one or more
sides.
Slab-on-grade - A type of house construction where
the bottom floor of a house is a slab that is no more
than about 1 ft below grade level on any side of the
house.
Smoke stick - A small tube, several inches long,
which releases a small stream of inert smoke when a
rubberbulbatoneendof the tube iscompressed. Can
be used to define visually bulk air movement in a small
area, such as the direction of air flow through small
openings in slabs and foundation walls.
Soil gas - Gas that is always present underground, in
the small spaces between particles of the soil or in
crevices in rock. The major constituent of soil gas is
air with some components from the soil (such as
radon) added.
Stack effect - The upward movement of house air
when the weather is cold, caused by the buoyant force
of the warm house air. House air leaks out at the upper
levels of the house, so that outdoor air (and soil gas)
must leak in at the lower levels to compensate. The
continuous exfiltration upstairs and infiltration down-
stairs maintain the stack effect air movement, so
named because it is similar to hot combustion gases
rising up a fireplace or furnace flue stack.
40
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Glossary (cont.)
Sump - A pit through a basement floor slab, designed
to collect water and thus avoid water problems in the
basement. Water is often directed into the sump by
drain tiles around the inside or outside the footings.
Ventilation rate - The rate at which outdoor air enters
the house, displacing house air. The ventilation rate
depends on the tightness of the house shell, weather
conditions, window and door openings, and the opera-
tion of appliances (such as fans) influencing air move-
ment. Commonly expressed in terms of air changes
per hour, or cubic feet per minute.
WC - The height (in inches) of a water column that
represents a unit of measure for pressure differences.
41
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