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EPA 520/1-89-020
RADON REDUCTION TECHNIQUES IN SCHOOLS
Interim Technical Guidance
Office of Radiation Programs
Office of Air and Radiation
and
Air and Energy Engineering Research Laboratory
Office of Research and Development
United States Environmental Protection Agency
Washington, DC
October 1989
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EPA DISCLAIMER NOTICE
The U.S. Environmental Protection Agency (EPA) strives to provide accurate, complete, and useful
information. However, neither EPA nor any person contributing to the preparation of this document
makes any warranty, expressed or implied, with respect to the usefulness or effectiveness of any
information, method, or process disclosed in this document
Mention of firms, trade names, or commercial products in this document does not constitute
endorsement or recommendation for use.
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ACKNOWLEDGMENTS
The information contained in this technical document is based largely on research conducted in
Washington County, Maryland, by the Air and Energy Engineering Research Laboratory (AEERL) of
EPA's Office of Research and Development and their contractor, INFILTEC. The research was
conducted with the assistance of H. Winger of the Washington County Schools (Maryland).
A.B. Craig and K.W. Leovic of AEERL and D. W. Saum of INFILTEC contributed to authorship of this
document. F. L. Blair in the Radon Division of EPA's Office of Radiation Programs (ORP) served as
Work Assignment Manager for contractor support. J. Harrison also of ORP's Radon Division provided
substantive information and comments. Of the contributors outside of EPA, we are particularly indebted
to T. Brennan of Camroden Associates and W. A. Turner of Harriman Associates for their input.
Drafts of this document have been reviewed by a large number of individuals in the Government and in
the private and academic sectors. Comments from these reviewers in addition to those from the
individuals listed above have helped significantly to improve the completeness, accuracy, and clarity of
the document. The following reviewers offered substantial input: A. Persily of the National Institute of
Standards and Technology; P.A. Giardina and L. G. Koehler of EPA Region 2; W.E. Bellanger of EPA
Region 3; F. P. Wagner of EPA Region 4; R. Dye of EPA Region 7; L. Feldt, J. Hoornbeek, D.
Murane, and L. Salmon of ORP's Radon Division; J. Puskins of ORP's Analysis and Support Division;
C. Phillips of Fairfax County Public Schools (Virginia); D. Shiftlet of Prince George's County Schools
(Maryland); H. M. Mardis of Environmental Research and Technology, Inc.; R. J. Shaughnessy of the
University of Tulsa; T. Meehan of Safe-Aire; G. Bushong and R. McNally of EPA's Office of Toxic
Substance's Asbestos Program. Technical editing was provided by W. W. Whelan of AEERL and I.
McKnight of ORP.
iii
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CONTENTS
Page
ACKNOWLEDGMENTS iii
1 INTRODUCTION 1
1.1 Purpose 1
1.2 Additional Sources of Information 1
1.3 Radon Facts ., 2
2 RADON MITIGATION 5
2.1 Radon Entry 5
2.2 Radon Variations Within Schools . 6
2.3 Radon Mitigation Techniques 6
3 ANALYZING THE PROBLEM 9
4 CRITICAL SCHOOL BUILDING COMPONENTS 11
4.1 School Substructures 11
4.2 HVAC Systems 12
4.3 Location of Utility Lines 14
5 DESIGN AND INSTALLATION OF SUBSLAB DEPRESSURIZATION
(SSD) SYSTEMS 15
5.1 Application 15
5.2 Diagnostic Testing 15
5.3 Design and Installation 17
6 OTHER APPROACHES TO RADON REDUCTION 23
6.1 Classroom Pressurization 23
6.2 Increasing Ventilation 24
6.3 Crawl Space Depressurization 24
7 SPECIAL CONSIDERATIONS 25
7.1 Building Codes 25
7.2 Worker Protection '.. . 25
7.3 Asbestos 25
REFERENCES
27
IV
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APPENDIX A: TECHNICAL INFORMATION 29
A.1 Using Construction Documents . . 29
A.2 Fan and Pipe Selection 30
A3 Diagnostic Measurement Tools 32
A4 Installation Tools 33
AS School SSD Installation Variations 33
APPENDIX B: SCHOOL MITIGATION CASE STUDIES 35
School A' Prince George's County, MD 35
School B: Washington County, MD 36
School C: Washington County, MD 40
School D: Washington County, MD 41
School E: Fairfax County, VA [42
School F: Washington County, MD . 44
School G: Arlington County, VA 45
School H: Washington County, MD 46
APPENDIX C: STATE RADON OFFICES AND EPA REGIONAL RADIATION PROGRAM
OFFICES 49
State Radon Offices 49
EPA Regional Offices 53
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1. INTRODUCTION
l.l
PURPOSE
This technical document is intended to assist
school facilities maintenance personnel, State
officials, and other interested persons in the
selection, design, and operation of radon
reduction systems in schools. School officials
should work in conjunction with a person
experienced in radon mitigation, preferably in
schools, to diagnose the problem and determine
which mitigation options are feasible. School
officials can contact their State Radon Office or
EPA Regional Office for guidance on selecting
a qualified radon mitigation contractor. (See
Appendix C.)
The guidance contained in this document is
based largely on research conducted in 1987 and
1988 in schools located in Maryland and
Virginia. In these initial efforts, researchers
from the U.S. Environmental Protection Agency
(EPA) adapted radon reduction techniques
proven successful in residential housing and
installed them in eight schools. Results indicate
that radon mitigation and diagnostic techniques
developed for houses can be applied successfully
in these schools. The applicability of these
mitigation approaches to other schools will
depend on the unique characteristics of each
school.
Because school design, construction, and
operation patterns vary considerably, it is not
always possible to recommend "standard"
corrective actions that apply to all schools.
Costs for radon reduction will also be school
specific and will depend on the initial radon
level, the extent of the radon problem in the
school, the school design and construction, the
design and operation of the heating, ventilating,
and air-conditioning (HVAC) system, and the
ability of the school maintenance personnel to
participate in the diagnosis and mitigation of
the radon problem. With the guidance of an
experienced radon mitigator, maintenance
personnel may be able to install radon reduction
systems themselves.
This technical document covers background
information on radon and radon mitigation
experience, important school building
characteristics relative to radon entry and
mitigation, problem analysis, radon diagnostic
testing, and radon mitigation system design and
installation. Appendices include technical
information, case studies of the Maryland and
Virginia schools mitigated, and lists of State
Radon Offices and EPA Regional Radiation
Program Offices.
It is important to understand that this is
preliminary guidance. A major research
program is under way in the Air and Energy
Engineering Research Laboratory in EPA's
Office of Research and Development, and
guidance on recommended radon reduction
actions for schools will be updated as soon as
possible.
1.2 ADDITIONAL SOURCES OF
INFORMATION
The publications listed below are available from
State Radon Offices or from EPA Regional
Offices. (See Appendix C.)
PUBLICATIONS ON RADON IN SCHOOLS
For guidance on how to measure radon levels in
schools, you should consult "Radon
Measurements in Schools - An Interim Report"
(EPA 520/1-89-010).
OTHER PUBLICATIONS ON RADON
EPA has been studying the effectiveness of
various methods of reducing radon
concentrations in houses. Although this work is
not yet complete, considerable progress has
been made over the last several years, and a
number of EPA publications have been issued.
A general familiarity with these publications on
radon reduction in houses will be useful in
understanding and reducing elevated radon
levels in school buildings.
"A Citizen's Guide to Radon: What It Is And
What To Do About It" (EPA OPA-86-004)
provides general background information for the
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homeowner on radon and its associated health
risks. It should be noted that this guide is
being updated, and the next edition should be
available in mid-1990.
"Radon Reduction Methods: A Homeowner's
Guide" (Second and Third Editions)
(OPA-87-010 and OPA-89-010) describe in
general terms the various radon reduction
methods available to homeowners.
"Radon Reduction Techniques for Detached
Houses: Technical Guidance" (Second Edition)
(EPA/625/5-87/019) is a reference manual
providing information on the sources of radon
and its health effects as well as detailed
guidance on the selection, design, installation,
and operation of radon reduction systems.
"Application of Radon Reduction Methods"
(EPA/625/5-88/024) supplements the second
edition of the technical manual (above) as a
decision guidance document directing the user
through the steps of diagnosing a radon
problem and selecting a radon reduction
approach. Mitigation system design, installation,
and operation are also detailed.
"Radon Reduction in New Construction, An
Interim Guide" (EPA OPA-87-009) and
"Radon-Resistant Residential New Construction"
(EPA-600/8-88-087) provide information on
radon prevention techniques for new
construction.
13 RADON FACTS
1.3.1 Radon Gas
Radon is a colorless, odorless, and tasteless
radioactive gas which results from the decay of
uranium. Since uranium occurs naturally in
small quantities in most rocks and soil, radon is
continually released into soil gas, underground
water, and outdoor air. Radon is chemically
inert, and it moves freely without combining
with other materials. In outdoor air the radon
emitted from the soil is quickly diluted to very
low concentrations. However, relatively high
concentrations of radon can accumulate inside
buildings if radon-containing soil gas infiltrates
into the building through openings such as
cracks, building joints, and utility penetrations.
Normal building ventilation may dilute the
incoming radon gas, but depending on the soil
gas radon levels and the amount of soil gas
entry, the radon concentration in the building
may accumulate to high levels. Since radon
source strengths vary and radon entry routes are
so unpredictable, testing each building is the
only practical way to determine the extent of
the problem.
EPA currently recommends taking action to
reduce radon levels in homes where the annual
average concentration of radon exceeds 4
picocuries per liter (pCi/L). (As a comparison,
average outdoor radon concentrations tend to
range from about 0.1 to 0.2 pCi/L.) The greater
the reduction in radon, the greater the
reduction in health risk. Consequently, an
effort should be made to reduce radon levels in
all buildings as far below 4 pCi/L as possible.
It should also be noted that the 1988 Indoor
Radon Abatement Act establishes as a national
long-term goal that the air within buildings be
as free of radon as the air outside of the
buildings.
1.3.2 Health Effects
Radon differs from most other carcinogens in
that human epidemiological evidence links
radon to lung cancer, and this evidence is well
supported by laboratory studies and
experimental research. Although uncertainties
remain and considerable research is continuing
in this field, the health risks of radon have been
clearly recognized by the National Academy of
Sciences, the U. S. Public Health Service, and
EPA.
Lung cancer is the only health risk which
significant data clearly associate with radon.
Radon gas decays into other radioactive
elements (often referred to as radon decay
products or radon progeny) which can lodge in
the lungs. Bombardment of sensitive lung tissue
by alpha radiation released from the decay
products can increase the risk of lung cancer. It
is estimated that radon causes roughly 20,000
lung cancers each year in the United States.
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It should be emphasized that estimates of the
number of lung cancers resulting from radon
vary widely, but even the lowest estimate
represents the largest cause of lung cancer for
non-smokers. Not everyone exposed to elevated
levels of radon will develop lung cancer.
However, most scientists believe that children
are at an equal or greater risk from exposure to
radon than adults and that smokers are at a
greater risk from exposure to radon than
nonsmokers. There is also consensus among
scientists that the risk of developing lung cancer
increases as the concentration and length of
exposure increase.
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2. RADON MITIGATION
Since 1984, when elevated levels of indoor
radon were discovered in the Reading Prong
area of Pennsylvania, many thousands of houses
have had radon reduction systems installed. In
many areas of the United States, it is not
uncommon to find a contractor with house
mitigation experience. In fact, many states
maintain lists of radon mitigation contractors.
(See Appendix C for a list of State Radon
Offices.)
Radon mitigation experience in schools is
relatively recent. However, initial research
indicates that radon reduction technologies
proven successful in houses are applicable to
some schools. The applicability of these
mitigation approaches to other schools will
depend on the unique characteristics of each
school.
2.1
RADON ENTRY
Radon normally enters a building from soil gas
that is drawn in by pressure differentials
between the soil surrounding the substructure
and the building interior. If the building
interior is at a lower pressure than the soil
surrounding the substructure and radon is
present in the soil, the radon can be pulled in
through cracks and openings that are in contact
with the soil. The amount of radon in a given
classroom will depend on the level of radon in
the underlying material, the ease with which the
radon moves as a component of the soil gas
through the soil, the magnitude and direction of
the pressure differentials, and the number and
size of the radon entry routes.
2.1.1 Causes of Pressure Differentials
Pressure differentials that contribute to radon
entry can result from operation of an HVAC
system under conditions that cause negative
pressures (in the building relative to the subslab
area), indoor/outdoor temperature differences
(including the "stack effect"), use of appliances
or other mechanical devices that depressurize
the building, and wind.
HVAC systems in schools and other large
buildings vary considerably and tend to have a
much greater impact on radon levels than do
heating and air conditioning systems in houses.
If the HVAC system induces a negative pressure
in the building relative to the subslab area,
radon can be pulled into the building through
floor and wall cracks or other openings in
contact with the soil.
Even if the HVAC system does not contribute
to pressure differentials in the building, thermal
stack effects can induce localized negative
pressure at the base of the building causing
radon-containing soil gas to be pulled into the
school. As air inside the structure is heated, it
becomes less dense, and rises, exiting out
through openings in the top of the structure.
Cooler air is drawn into the building to replace
the warm air leaving at the top of the structure.
This phenomenom, which acts much like a
chimney, is referred to as the stack effect.
If the HVAC system pressurizes the building,
which is common in many systems, it can
prevent radon entry as long as the fan is
running. However, school HVAC systems are
normally set back or turned off during evenings
and weekends, and even if the HVAC system
pressurizes the school during operation, indoor
radon levels may build up during setback
periods. Once the HVAC system is turned back
on, it may take several hours for radon levels to
be adequately reduced. Adjustment of the
setback timing may, in some cases, achieve
acceptable indoor radon levels during periods of
occupancy. Measurements with continuous
radon monitoring equipment in each classroom
with elevated radon levels are necessary to
determine the appropriate setback configuration
in such situations.
2.1.2 Radon Entry Routes
Typical radon entry routes include cracks in the
slabs and walls, floor/wall joints, porous
concrete block walls, open sump pits, and
openings around utility penetrations. Radon
accumulated in crawl spaces may also enter a
building. In addition, many schools have other
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radon entiy points such as slab pour joints
(control joints) and subslab utility tunnels.
These are discussed in more detail in Section
4.3, Location of Utility Lines.
In houses, radon problems caused by radon
emanations from building materials or by radon
released from radon-contaminated water
(normally well water) occur in isolated
instances. We would expect few schools to
have this type of radon problem.
2.2 RADON VARIATIONS WITHIN
SCHOOLS
Experience has shown that there can be large
differences between radon levels in classrooms
on the same floor. Causes for these
room-to-room differences are thought to include
variations in the soil under the class rooms,
variations in the construction between rooms,
variations in the number and size of cracks in
different rooms, and variations in the design and
operation of the HVAC system. This
room-to-room variability makes it difficult to
detect and mitigate all the rooms with high
radon levels unless every classroom on or below
ground is tested.
23 MITIGATION TECHNIQUES
Although the selection of the most appropriate
radon mitigation technique depends on the
unique characteristics of each building, five
mitigation approaches have been common in
house mitigation, either alone or in
combination. These include: subslab
depressurization (SSD), submembrane
depressurization (SMD) in crawl space areas,
sealing, pressurizatfon, and natural and
mechanical ventilation. (For additional details
on these and other mitigation techniques for
houses, refer to the technical manuals previously
referenced.)
These techniques and their applicability to
schools are briefly discussed below. Because
current radon mitigation experience in schools is
largely limited to SSD, this guidance document
focuses on that approach. Where available,
guidance for other techniques is also given.
The reader should review Sections 5 and 6 for
more detail.
EPA feels that many of the radon reduction
approaches for houses will be applicable to
school mitigation, and research is in progress to
conduct additional testing of these techniques in
school buildings. It should be understood that
in many types of schools there is little or no
experience in radon mitigation. Examples of
schools that may be difficult to mitigate include:
schools with poor subslab permeability
(explained under SSD); schools with subslab
ductwork; schools with exhaust fans to increase
fresh-air infiltration (potentially causing large
negative pressures and increased radon entry);
and schools constructed over crawl spaces.
2.3.1 Subslab Depressurization (SSD)
SSD has been the most successful and widely
used radon reduction technique in slab-on-grade
and basement houses. Installation of an SSD
system involves inserting pipes through the
concrete slab to access the crushed rock or soil
beneath. A fan is then used to suck
radon-containing soil gas from under the slab
through the pipes, releasing it outdoors. SSD
works by creating a negative pressure field
under the slab relative to the building interior;
this interior/exterior pressure relationship
prevents radon-containing soil gas from entering
the building.
The material under the foundation slab must be
permeable enough to allow air movement under
the slab so that adequate suction can be induced
across the entire slab. (Subslab permeability or
air flow is often referred to as subslab
"communication" or "pressure field extension.")
When subslab pressure field extension is
inadequate, additional suction pipes may be able
to increase the area that can be depressurized.
Initial results indicate that SSD can successfully
reduce radon levels in some schools by over 90
percent if crushed aggregate or other permeable
material is under the slab to allow for adequate
pressure field extension. However, schools with
poor subslab communication and those using
return-air ductwork beneath the slab may
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require an alternative mitigation approach to
SSD.
2.3.4 Pressurizatidn (Through HVAC System
Controlt
2.3.2 SubmembraBe Depressurization (SMD't
A variation of SSD, often referred to as
submembrane depressurization (SMD), bas been
very successful in reducing radon levels in
houses constructed over crawl spaces. A
polyethylene or rubber membrane is laid over
the earth floor and sealed to the crawl space
walls and internal piers. Suction is applied to
the soil underneath the membrane and the soil
gas is exhausted to the outdoors. EPA has not
yet researched this method in schools; however,
SMD may prove more difficult in many school
crawl spaces because of all the internal
foundation walls, the large areas to be treated,
and the possible presence of asbestos.
2.3.3 Sealing
The effectiveness of sealing alone as a radon
reduction technique is limited by the ability to
identify, access, and seal major radon entry
routes. Most buildings have so many radon
entry routes that sealing only the obvious ones
may not result in a significant degree of radon
reduction. Complete sealing of all radon entry
routes is often impractical. In some buildings,
certain areas will be difficult, if not impossible,
to access and/or seal without significant expense.
In addition, settling foundations and expanding
floor cracks continue to open new entry routes
and reopen old ones. Typical initial radon
reduction from extensive sealing in houses is
usually about SO percent
A potential mitigation approach for schools is
adjustment of the air-handling system to
maintain a positive pressure in the school
relative to the subslab area, discouraging the
inflow of radon. This technique, referred to as
pressurization, has been shown to be an
effective temporary means of reducing radon
levels in some schools, depending on the design
of the HVAC system. If pressurization through
the HVAC system is under consideration as a
long-term radon mitigation solution in a given
school, proper operation and maintenance of
the system are critical. Responses to changes in
environmental conditions and any additional
maintenance costs and energy penalties
associated with the changes in operation of the
HVAC system must also be carefully considered.
There may also be potential moisture and
condensation problems if pressurization is
implemented in very cold climates.
2.3.5 Increasing BuildingVentilation (Without
HVAC System Control)
An increase in building ventilation rate, by
opening lower-level windows, doors, and vents
or by blowing outdoor air into the building with
a fan, reduces radon levels by diluting indoor air
with outdoor air and by minimizing the pressure
differentials that draw radon into the building.
However, EPA's preferred radon reduction
strategy has been to prevent radon entry into
buildings, rather than to reduce radon levels
once it has entered. Experience has shown that
it is usually impractical to lower radon levels in
houses much more than 50 percent through
increased ventilation. Therefore, in most
climates, reducing radon levels through
ventilation should only be considered as a
temporary measure.
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3. ANALYZING THE PROBLEM
Understanding a school radon problem and
developing a mitigation strategy involves a
careful review of all 'radon testing data, a
walk-through audit, and a review of relevant
building documents. Applicable critical building
components (as discussed in Section 4) should
be examined. These include the building
structure, the HVAC system, and the location of
utility lines. Special radon diagnostic tests will
also be useful. These might include continuous
monitoring of radon levels during various
building operating conditions, mapping of
subslab radon, and measuring subslab
communication and pressure field extension to
determine if SSD is applicable. Diagnostic tests
are discussed in more detail in Section 5. A
general outline of the steps involved follows.
STEP 1: REVIEW RADON TEST
RESULTS
Write down all radon test results on copies of
the school floor plan so that rooms with high
readings can be correlated. Test data should
include type of measurement device, length of
measurement period, HVAC operating
conditions, school occupancy, and weather
conditions during the test period. In developing
a mitigation plan, emphasis should be on the
confirmatory measurements rather than the
screening measurements, as described in "Radon
Measurements in Schools - An Interim Report".
(See Section 1.2, Additional Sources of
Information.)
STEP 2:
WALK-THROUGH AUDIT
Thoroughly examine all parts of the building in
contact with the soil (In a basement school,
examine both the basement and first floor.)
Note the presence of possible radon entry
routes such as floor/wall cracks and other
openings to the sofl and determine if they
correlate with areas having elevated radon
levels.
STEPS:
EVALUATE HVAC SYSTEM
(either positive or negative) can be exerted
during system operation. Where possible,
obtain a complete description of the HVAC
system design and operation from the building
facilities personnel and determine if HVAC
operation is causing any negative pressures in
the building relative to the subslab area. If the
original school has any additions, be sure to
note if there are different types of HVAC
systems, as well as structural differences between
the additions. In some cases, consultation with
a qualified firm experienced in HVAC system
design may be useful in understanding possible
sources of HVAC depressurization.
STEP 4:
REVIEW BUILDING PLANS
Depending on the design and operation of the
HVAC system, relatively strong indoor pressures
Study the foundation plans and specifications
for information on aggregate or gravel beneath
the slab, for the layout of footings and subslab
walls that could limit subslab communication in
an SSD system, and for the presence of subslab
ductwork.
STEP 5: CONSULT EXPERIENCED
MITIGATORS
School personnel with little experience in radon
reduction should use experienced or certified
radon mitigation firms to gain the advantage of
their experience and specialized knowledge of
local problems. These firms may also be able
to provide specialized equipment such as
continuous radon monitors, core drills, and
sensitive pressure gauges. Since radon
mitigation in schools is a relatively new field, it
is probable that mitigators in many parts of the
country will be more experienced in mitigation
of houses than schools.
Local and state health departments and EPA
regional offices maintain lists of persons who
have attended EPA mitigation training courses.
Several states have initiated programs for
certification of radon mitigation companies, and
several trade associations have been offering
membership or educational courses for
professionals in the field. In 1990, EPA will
publish a national list of mitigators who have
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met the requirements of the Radon Contractor
Proficiency Program.
STEP 6: PLAN MITIGATION
STRATEGY
Radon mitigation is not an exact science. In
schools it is often best to proceed in phases:
install the simplest system that promises the
biggest payback and re-test to determine
effectiveness; then use this information to
proceed with subsequent phases, as necessary.
The phased approach should be especially
helpful in schools because experience is limited
and the buildings tend to be more complex than
houses. Because we often do not know all the
radon entry routes or forces drawing radon into
the building, the first phase of mitigation can
usually provide valuable information. The
following sections cover the critical building
components relative to radon entry and
mitigation, the design and installation of SSD
systems, and other mitigation approaches. The
case studies in Appendix B are examples of the
phased approach to mitigation.
10
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4. CRITICAL SCHOOL BUILDING COMPONENTS
For help in understanding the causes of elevated
radon levels in schools and to better design
school mitigation systems, three building
components are of primary concern: the
building substructure(s), the design and
operation of the HVAC system(s), and the
location of utility lines. This section discusses
how these aspects of school buildings relate to
house mitigation experience, how these building
components tend to affect radon entry in
schools, and how they may impact mitigation
system design and operation.
An understanding of these critical building
components and how they relate to a specific
situation are important when designing a school
mitigation system.
4.1
SCHOOL SUBSTRUCTURES
The three basic substructure types are
slab-on-grade, basement, and crawl space. The
majority of substructures in the school districts
studied thus far were slab-on-grade. Schools
often have one or more additions, and each
addition may have a different type of
substructure.
Because of larger building and room sizes,
schools often have interior footings and subslab
foundation elements. These may create subslab
communication barriers between areas. The
location of subslab barriers and their influence
on subslab communication will depend on
building size and configuration, and on
architectural preferences for carrying roof load.
The locations of these barriers may affect the
number and placement of SSD suction points in
a slab-on-grade or basement structure, and
foundation plans, if available, should always be
examined when selecting suction point locations.
This increases the opportunity for all areas with
elevated radon levels to be adequately treated by
the SSD system.
4.1.1 Slab-on-Grade
Since current research indicates that SSD is the
most successful technique for reducing radon
levels in slab-on-grade schools with good
subslab communication, the construction
documents should be checked for information
on the type and amount of subslab gravel or
aggregate. Even if aggregate is specified, the
air-flow resistance of different aggregate types
has been found to differ significantly. Subslab
communication measurements and visual
inspections are often necessary to efficiently
design an SSD system.
Interior footings and rolled footings (grade
beams) may pose substantial barriers to
communication between areas; therefore, it is
necessary to carefully examine the foundation
plans when designing an SSD system.
Depending on the type of subslab barrier and
the material underneath the barrier (e.g., clay,
sand, gravel) there may be limited
communication, if any, across these barriers.
Often, it may be necessary to locate additional
subslab suction points if areas to be mitigated
do not communicate across subslab barriers. In
other cases, coverage of the SSD system may be
increased if a larger fan and/or pipe diameter
are used. Evaluation of subslab communication,
as discussed in Section 5.2, will indicate the
effect that these subslab barriers will have on
SSD system design.
4.1.2 Basements
Schools with basements may present a difficult
problem because a large area is in contact with
the soil. Some school basements are completely
below-grade and others are walk-out basements.
Walk-out basements are commonly used as
classrooms or workspace. Many full basements
in older buildings have also been converted to
classroom space. Below-grade walls, the slab,
and floor/wall cracks can be significant sources
of radon entry. If there is adequate subslab
communication, SSD is probably the most
desirable approach to radon mitigation in most
basement schools. All of the comments on SSD
systems in the above section on slab-on-grade
schools are applicable to basement schools. In
addition, any asbestos in the basement should
be removed or encapsulated according to the
Asbestos Hazard Emergency Response Act
11
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(AHERA) before attempting any radon
reduction activities in the basement.
4.1.3 Crawl Spaces
Most crawl space schools tend to be constructed
on concrete slabs supported by periphery and
internal foundation walls, although schools with
conventional wood joist and floor construction
over a crawl space and "portable" classrooms do
exist. Crawl spaces are usually divided into
compartments that are all interconnected by
open passages allowing access to utility pipes.
To avoid freezing of inadequately insulated
pipes, some school crawl spaces have no vents.
As a result, high levels of radon may collect in
the crawl space. (Elevated levels of radon can
accumulate in a vented crawl space as well.)
Increasing natural ventilation by opening crawl
space vents may be a possible solution as long
as the changes in temperature do not cause
problems such as freezing pipes, condensation,
or cold floors. Whether this will adequately
reduce radon levels will be school specific.
Depressurization of the crawl space has been
more effective in reducing radon levels in
houses than natural ventilation of the crawl
space; again, experience in schools has been
limited. Submembrane depressurization (SMD)
has also been successful in reducing radon levels
in houses built on crawl spaces. However, SMD
has not yet been researched by EPA in any
schools. It is possible that the application of
this technique may be difficult in many schools
because of the large area to be treated and
complicating interior crawl space walls.
More detailed guidance on these approaches for
schools will be available following further
research. In any case, any asbestos in the crawl
space area should be removed or encapsulated
according to AHERA before attempting any
radon reduction activities in the crawl space.
4.2 HEATING, VENTILATING, AND
AIR-CONDITIONING (HVAC)
SYSTEMS
Understanding the school's HVAC system often
plays an important role in determining the
source of, and the solution to, the radon
problem. The American Society of Heating,
Refrigerating and Air-Conditioning Engineers
(ASHRAE) Standard 62-1981R "Ventilation for
Acceptable Indoor Air Quality" should be
consulted to determine if the installed HVAC
system is designed and operated to achieve
recommended minimum ventilation standards
for indoor air quality. Sometimes schools and
similar buildings were not designed with
adequate ventilation, and in other instances,
ventilation systems are not operated properly
due to factors such as increased energy costs or
uncomfortable conditions caused by a design or
maintenance problem. It is advisable to achieve
the recommended minimum ventilation
standards in a school in conjunction with or in
addition to installation of a system for radon
reduction. Consultation with a qualified HVAC
firm or a registered Professional Engineer
experienced in HVAC system design is
recommended for evaluating the HVAC system
both in terms of radon mitigation options and
indoor air quality.
HVAC systems in the school districts initially
researched by EPA include: central air-handling
systems, room-sized unit ventilators, and radiant
heat. Unit ventilators and radiant heat can exist
with or without a separate ventilation system.
Central air-handling systems and unit ventilators
tend to be most prevalent in newer schools,
particularly if air-conditioned. Often, because of
additions, schools may have more than one type
of HVAC system.
4.2.1 Central-Air Handling Systems
In many buildings with air-conditioning, the
HVAC system contains some type of central
air-handling system. The systems can vary
widely in size and configuration, and the
different types of systems will tend to have
unique effects on radon entry and subsequent
mitigation. Three types of central air-handling
systems common in schools are summarized
below: single-fan systems, dual-fan systems, and
exhaust-only systems.
In single-fan systems the air is distributed to the
rooms (normally under pressure) by the
air-handling fan, and the return air is brought
12
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back by the same fan. These systems are similar
to forced-air systems in houses, except that fresh
air can usually be mixed with the return air.
The air-handling fans may operate continuously
during the day, or they may operate only when
heated or cooled air is required, cycling on and
off throughout the day with thermostat control.
In any case, the systems are normally set back
or turned off during evenings and weekends.
These single-fan systems are normally designed
to generate neutral or positive pressures in all
rooms. In a single-fan system, stale air leaves
the building either through a separate exhaust
system, by relief, or by exfiltration through
cracks and openings due to overpressurization
by the fan (if fresh air is brought into the
system).
Larger air-handling systems often employ a
dual-fan system: an air-distribution fan and a
smaller return-air fan. The return-air fan allows
for forced exhaust of return air. Louvers
regulate the amount of fresh air brought into
the air supply and the amount of return air that
is exhausted. Dual-fan systems are usually
designed so that they generate positive pressures
in all rooms when operating; however, if the
return-air fan pulls more air from a room than
the supply fan is furnishing, then the room can
be run under negative pressure causing soil gas
to enter the room through openings to the soil
beneath the slab. The fans usually operate
continuously during the day and are either set
back or turned off during evenings and
weekends.
Although single- and dual-fan systems are
commonly designed to operate at positive or
neutral pressures, pressure measurements in
schools have indicated that such systems can
cause significant negative pressures in the
building. HVAC system modifications (such as
reducing the amoral of fresh-air intake), lack of
maintenance (suck as dirty filters), unrepaired
damage, or other factors can result in
substantial negative pressures in some rooms,
thus increasing soil gas entry.
The third type of central air-handling system is
an exhaust-only system in which no supply air is
provided mechanically. Such systems are
generally used for ventilation in schools that
heat with radiant systems or unit ventilators and
have no central air-handlers. The fans exhaust
air through a central ceiling plenum above the
rooms or with roof mounted exhausts in many
locations. These systems are designed to draw
fresh air into the rooms by infiltration through
above grade cracks and openings; however,
radon can enter through below grade cracks and
openings. The fans in exhaust-only systems
usually are normally off at night but may
operate continuously during the day. This can
generate a negative pressure in all rooms and,
consequently, increase the potential for radon
entry.
4.2.2 Unit Ventilators
These self-contained units provide heating
and/or air-conditioning in individual rooms.
They are usually installed on outside walls with
an enclosure which contains finned radiators
and/or coils. They can also be located overhead
in each room and are sometimes above the
drop ceiling. Unit ventilators normally contain
one or more fans and a vent to the outdoors so
that fresh air can be pulled in by the fah(s).
An adjustable damper allows a variation in the
mix of recycled room air and fresh air fed to
the circulating fan. Fresh-air intake can be
minimal because of obstruction of the outdoor
vents due to poor maintenance or energy
conservation practices. (Units that do not
provide any outdoor air by design are referred
to as fan coil units, not unit ventilators.)
In some cases there is a central-building
exhaust-fan system in schools with unit
ventilators, as discussed above. This exhaust fan
is intended to provide ventilation by pulling air
in through the unit ventilators (if their fresh-air
vents are open), but it also creates a significant
negative pressure in the room. . This negative
pressure can pull radon into the rooms with the
soil gas. If fresh-air intakes in the unit
ventilators are blocked for any reason, operation
of exhaust-only fans will increase the negative
pressure in the building relative to the subslab
area.
Radon mitigation strategies in schools with unit
ventilators might include (1) opening the
fresh-air vents to improve ventilation and
13
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running the unit ventilator fans continuously to
pressurize the room, (2) replacing an
exhaust-only ventilation system with a system
that operates under a slight positive pressure, or
(3) installation of an SSD system that could
overpower all negative pressures in the building.
If the current HVAC system is providing
adequate ventilation to the building or if
options (1) and (2) are not feasible, option (3),
SSD, would be the most practical strategy if
there is good subslab communication.
4.2.3 Radiant Heat Systems
Radiant heat systems in schools tend to be of
three types: hot water radiators, baseboard
heaters, or warm water radiant heat within the
slab. Schools heated with radiant systems
should have a ventilation system to achieve the
fresh air requirements recommended by
ASHRAE; however, many of these schools
provide no ventilation other than infiltration.
In other schools, there are exhaust ventilators
on the roof. These can be passive, allowing
some ventilation through the stack effect, or
they can be powered. Powered Roof
Ventilators (PRVs) can cause significant
building depressurization, particularly if a fresh
air supply is not provided. This can cause
considerable radon entry into the building while
such exhaust systems are operating.
If SSD is under consideration as a mitigation
option in a school with intra-slab radiant heat,
the building plans should be carefully studied to
avoid damaging any piping when placing the
SSD points. An infrared scanning device can be
used to help locate the exact position of subslab
pipes. Satisfactory locations for SSD pipes may
be very limited in such schools.
43 LOCATION OF UTILITY LINES
The location of entry points for utility lines can
have a significant influence on radon entry in
schools since they can provide an entry route
from the soil into the indoor air. Utility line
locations depend on many factors such as
substructure type, HVAC system, and
architectural needs or practices. Utility lines
located above grade should not cause significant
radon entry problems.
In slab-on-grade and crawl space schools, the
utility penetrations from the subslab or crawl
space area to individual rooms are frequently
not completely sealed, leaving openings between
the soil and the building interior. For example,
there is a potential for radon entry around
plumbing penetrations and electrical conduits.
If utility lines, such as electrical conduits and
water and sewer pipes, are located under the
slab, their exact locations should be carefully
noted from the plans, and caution should be
taken when drilling holes through the slab
during diagnostic measurements. This is
discussed in more detail in Section 5.
In some slab-on-grade schools, the utility lines
are located in a subslab utility tunnel that tends
to follow the building perimeter or central hall.
Utility tunnels often have many openings to the
soil beneath the slab-on-grade and,
consequently, can be a potential radon entry
route. In addition, risers to the unit ventilators
frequently pass through unsealed penetrations in
the floor so that soil gas in the utility tunnel
can readily enter the rooms. If the surrounding
soil has elevated radon levels, a utility tunnel
could be a major radon entry route in schools.
It is possible that the utility tunnel could be
used as a radon collection chamber for an SSD
system, and this approach will be studied. Any
asbestos in the utility tunnel should be removed
or encapsulated according to AHERA before
attempting any radon reduction activities in the
tunnel.
14
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5. DESIGN AND INSTALLATION OF SUBSLAB DEPRESSURIZATION (SSD) SYSTEMS
5.1
APPLICATION
Experience has shown that SSD is the most
successful radon reduction technique in houses
that have aggregate or permeable soil beneath
the slab. There is much less experience with
SSD in schools; however, the results to date,
although limited, have been promising in
schools that have aggregate or clean, coarse
gravel under the slab. Current guidance on
radon reduction in schools is focused on
designing and installing SSD systems, since
experience in mitigating schools using other
techniques (Section 6) is very limited.
Experience to date has identified certain types
of schools where SSD may not be applicable.
These include:
Schools that do not have crushed
aggregate, coarse gravel, or permeable
soil underneath the slab. (Experience
has shown that SSD systems perform
best when the subslab material is
approximately 3/4 to 1-1/4 inches in
diameter, with few fines.) An SSD
system may work in other situations if
enough suction points are installed to
create a sufficient pressure field.
However, in other cases an alternative
mitigation approach will be necessary.
Schools with subslab ductwork. In
house mitigation, the subslab ductwork
is sometimes sealed off and replaced
with new above-slab ductwork. This
could be difficult and expensive in, many
schools, and impossible in others.
Schools with crawl space construction.
Depending on crawl space size and
configuration, increased crawl space
ventilation, crawl space depressurization,
or submembrane depressurization
(SMD) may be applicable provided no
asbestos is present
Future school mitigation studies will research
radon reduction strategies for mitigating these
types of schools, and technical guidance will be
published as soon as possible. If diagnostic test
results or other reasons indicate that an SSD
system is not appropriate for a given school or
if an SSD system can not be installed as soon as
desired, refer to Section 6, Other Approaches to
Radon Reduction.
5.2
DIAGNOSTIC TESTING
Diagnostic measurements will help to better
understand the nature of the radon problem so
that an effective mitigation strategy can be
developed. Aggregate inspection and subslab
communication testing are the simplest, least
expensive, and most important diagnostics to
determine the applicability of an SSD system.
Other diagnostics require more expensive
equipment and may be more difficult to
interpret, but they also may be required to
understand the complex radon problems
associated with larger buildings and HVAC
system operation. Diagnostics that have proven
useful in school mitigation are described below.
5.2.1 Evaluation of the Footing Structure
It is important to determine the types and
locations of potential subslab barriers, such as
footings, subslab walls, and grade beams and
how they may impact subslab communication
and mitigation system design. The presence of
building walls does not necessarily indicate the
position of a footing or grade beam because not
all walls are load-bearing. The building plans
(foundation drawings) are the best source of
information on the location of footings. Note
that thickened areas of the slab (called "grade
beams") are sometimes found in schools to
support a block wall. Their effect on subslab
communication will depend on the depth of
aggregate or gravel under them.
Experience to date has shown that, in some
cases, subslab communication will reach across
these barriers. However, in many cases, areas
surrounded by footings, subslab walls, or grade
beams may each need at least one suction point.
(This is why the subslab communication test,
15
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which follows, is important in confirming the
presence, extent, and effects of subslab barriers.)
5.2.2 Evaluation of Subslab Communication
The most important parameter in assessing the
applicability of SSD is subslab communication
or pressure field extension. Permeable
aggregate, screened, coarse, and approximately
3/4 to 1-1/4 inches in diameter, is preferable.
Building plans and specifications have been
found to be generally accurate in determining
the presence of aggregate, but the aggregate
quality must be determined by inspection. If
aggregate is not mentioned in the specifications,
it may not be present even though it is shown
on the foundation drawings.
Subslab communication can be evaluated by
using a shop-type vacuum for suction at one
larger hole (normally located at the potential
SSD point) and pressure sensors at other
smaller holes. The suction hole should be at
least 1-inch in diameter or larger, and the test
holes should be approximately 3/8-inch in
diameter and should be located at various
distances and in various directions from the
suction hole, depending on building size and
configuration. This approach will indicate the
feasibility of developing a pressure field under
various parts of the slab and will also help to
identify the influence of subslab barriers such as
grade beams or below grade foundation walls.
It will also help to indicate competing pressures
or excessive leakage from subslab ductwork
which would inhibit pressure field development
in an SSD system.
Experience has shown that the size of the area
that can be mitigated by each SSD point varies
from a few hundred to several thousand square
feet The coverage will be dependent on
subslab communication, the flow capacity of the
fan and pipe, the presence of subslab barriers,
and on the strength of the building pressures
and leakage that the system must overcome. Of
course, if subslab permeability is limited, then
the pressure field may extend only a few feet
and many SSD points may be necessary to
adequately treat the entire area.
Pressures at the primary (1-inch plus) suction
point are typically measured at suctions of about
8, 6, 4, 2, and 0 inches WC The pressures at
the test hole can be measured either
qualitatively (with a smoke stick) or
quantitatively (with a pressure gauge). If
communication testing indicates a pressure of
0.001 inch WC (0.25 Pascal) or lower at a given
test hole or if smoke stick tests show that air
flows into the hole, it may be possible that an
SSD system will be able to reach the area.
This procedure requires an electric-pneumatic
hammer drill, a vacuum, and a sensitive pressure
sensor. Before drilling into the slab, utility
pipes and conduits should be noted from the
plans and confirmed to avoid drilling through
them. Refer to Section 7.2 on worker
protection for safety suggestions.
Aggregate quality can also be inspected by
drilling at least one hole in the slab, large
enough (at least 4-inches in diameter) to extract
a sample. Holes larger than 4-inches will allow
for a better estimate of the depth and porosity
of aggregate, but holes of this size may also
cause more damage to floor tiles and be more
difficult to repair. Again, proper precautions
should be taken when drilling through the slab.
Although this approach will indicate the
presence of subslab aggregate and the potential
for subslab communication, it will not indicate
the extent of pressure field development that is
possible with the communication test
5.23 Evaluation of Pressure Differentials
If the radon tests were made with the HVAC
system or other ventilation fans on, it may be
useful to re-test the rooms (at least the ones in
question) with aU fans turned off in order to
isolate the major sources of radon and to
determine if HVAC operation is influencing
radon levels. Changes in radon levels due to
HVAC operation may indicate the significance
of the pressures (both positive and negative)
generated by HVAC operation and the potential
for mitigation by HVAC modifications (See
Sections 4.2 and 6). Pressure differentials and
air flow measurements in classrooms can be
used to identify any HVAC flow imbalances that
may cause negative pressures in the building
16
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relative to the subslab area. These
measurements require sensitive pressure gauges
and/or air flow meters. Qualitative information
can be obtained by using a smoke stick to
indicate the direction of air flow.
If the HVAC system pressurizes the building, it
can prevent soil gas entry as long as the
air-circulating fan is running. However,
installation of an SSD system may still be
necessary if radon levels build up to
unacceptable levels inside the school when the
'fans are off and it takes too long to reduce the
radon to acceptable levels when the system is
turned back on.
If HVAC system operation or the natural stack
effect exerts a negative pressure in the building
relative to the subslab area, then a successful
SSD system must overcome this negative
pressure. Recent experience with SSD in a
limited number of schools indicates that a
well-constructed SSD system can provide
considerable reductions in radon despite strong
HVAC counter pressures. However, it may be
difficult for an SSD system to overcome the
negative pressures exerted by return-air ducts
located under the slab.
Continuous radon measurements (typically
averaged over 1-hour intervals) collected for
several days will show variations in radon levels.
These variations can result from changes in
HVAC operation, diurnal effects, weather
conditions, and occupancy patterns. These data
may lead to a greater understanding of the
pressure dynamics in the building; however, a
relatively expensive continuous radon monitor is
required. Continuous differential pressure
measurements (inside/outdoor/subslab) collected
concurrently with the continuous radon
measurements, are also extremely useful in
understanding HVAC system influence on radon
entry.
5.2.4 Measurement of Subslab Radon Levels
Subslab radon measurements are used to map
radon source strengths so that the suction
point(s) can be placed near the major sources.
The subslab radon measurements can be
collected through the 1/4-inch diameter holes
drilled into the slab in the subslab
communication test detailed above. To obtain
the most representative results, the subslab
radtin levels should be measured prior to the
communication test. This diagnostic technique
requires a hammer drill and a continuous or
grab radon monitor that can pump air samples
into a measuring chamber. Before drilling into
the slab, utility pipes and conduits should be
noted from the plans and confirmed to avoid
drilling through them.
53 DESIGN AND INSTALLATION
Installation of SSD systems is primarily a matter
of plumbing because of the extensive use of
PVC pipe. Electrical work, concrete work, and
roof work are often also involved. Due to the,
nature of the work, it is important that the
installer take into account all applicable codes
that may affect construction and/or
modifications to school buildings. Typically,
these may include electrical, mechanical, fire
protection, plumbing, and building codes
(Section 7).
A typical SSD system for a school is shown in
Figure 1 and should be referred to throughout
the section.
5.3.1 Suction Hole Location
The location of the suction hole is selected once
an area or room to be treated has been
identified based on radon measurements, subslab
communication tests, and any other diagnostic
measurements. For optimum mitigation it
would be best to locate the suction hole closest
to the highest known radon source. Of course,
if the rooms with higher radon levels are widely
separated, then they are probably independent
and must be treated separately. Often, the
source may be widespread or unidentified or the
suction hole may need to be located in an
out-of-the-way place that will cause minimum
disruption to the -room occupants.
Another consideration when locating suction
points is the accessibility of the exhaust pipe
and exhaust fan. In many cases the suction hole
position is chosen on the basis of aesthetics, fan
17
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Exhaust (released away from
• any air intakes or
J , open windows)
Exhaust Fan
Mounted Outiida
Optional Piping
Configuration
Drip Guard
Sealant
••••::.'i-v:;-i^i
\
Slope Horizontal Leg /
Down Toward Sub-slab L ,
H°"v ' ^-'_-_r --'
i i
Optional Piping
Configuration
/\
' T iTo Exhaust Fan
''ng »| i Mounted on Roof Roof Structur.
\
j.
bi m.
1
1
1
|
*
1
|
«:
/
^
^
Exit
Sch
' Connection to Other
Manifold Line -« Suction Point(s) if
, — — — — — applicable
Exit Piping (Minimum
Schedule 40 PVC)
Drop Ceiling
Note:
1. Closing of major slab openings
(e.g. major cracks, utility penetrations.
gaps «t the wall/floor joint) is important.
Verticil Drop
(Suction Pipe. Minimum
Schedule «O PVC)
Indoor Air Through Unctosod
Cracks. Joints. Utility
Openings. Etc.
Lip of undisturbed
aggregate/soil of
suffkaen- -vidthto
help support weight
of restored concrete
until set.
Undisturbed
• Soil
Figure 1. Typical Subslab Depressurization (SSD) Design for a School
-------
location, or exhaust pipe routing. Often a
location equidistant from both outside walls,
such as a hall or a closet on the hall side of a
classroom, is a good location if subslab
communication is sufficient
5.3.2 Pipe and Fan Layout
In order to adequately depressurize school slabs,
which may be much larger than house slabs,
larger fans and larger pipes to carry the
increased air flows are typically used. Appendix
A contains information on fan and pipe
selection which lists a number of fans with the
capability of drawing over 300 cubic feet per
minute (cftn) at 3/4-inch WC (which may be
three to four times the capacity of home
mitigation fans).
The typical 4-inch pipe used in most home
mitigation systems may have too much flow
resistance when used with this larger fan;
therefore, 6-inch pipe is often used. The
piping used should be fire-rated (minimum
Schedule 40 PVC).
If the permeability of the aggregate is high, then
a single 6-inch suction point can be used with
the larger pipe and fan. However, with typical
aggregate permeability, a wider area can be
mitigated by using two or three suction points
manifolded to one of the more powerful fans.
The location for the SSD point(s) should be
selected based on the results of the diagnostic
measurements. A typical manifold system might
consist of a 6-inch PVC pipe running
horizontally within a dropped ceiling and
extending 20- to 60-feet between vertical drops.
Connected to the manifold would be an exterior
mounted fan, and 4-inch PVC vertical pipes
which penetrate the slab and transmit vacuum
to that area of the floor slab. This arrangement
can be used to mitigate a long classroom wing
with the suction points located in the central
corridor or on the corridor side of a classroom.
Experience in schools has shown that locating
the suction points remote from the outside wall
will help to reduce short circuiting (satisfying
fan demand for air) of the system.
If any of the pipe is either outside the building
or in an unheated section of the building, then
condensation may form inside the pipe because
of the high moisture content of the exhausted
subslab &>il gas. The pipes should always be
slanted so that this condensation can drain back
into the subslab cavity where it originated.
(The in-line fans should be mounted vertically
to prevent water accumulation in the
bell-shaped housings.) Experience has shown
that SSD systems in homes can fail due to a
buildup of condensation in improperly oriented
fans and pipes. In humid climates, condensation
will also form on the outside of pipes in
exposed areas, and insulation or boxing in may
be necessary. Rain entry into uncapped exhaust
pipes has not been reported as a problem,
probably because the volume of rain is small
compared to the volume of condensation that is
continually flowing back down the exhaust pipes.
Ice buildup on the fan or on the exhaust stack
has not been reported as a significant problem,
probably because the soil gas is warm enough to
melt any ice or to prevent it from forming.
5.3.3 Suction Point and Pipe Installation
Once the location of a suction point is
determined, a hole must be drilled through the
concrete slab. Typically, the slab hole diameter
corresponds to the pipe's outside diameter,
usually slightly larger than 4- to 6-inches. The
hole must be large enough to accommodate the
suction pipe and to allow the excavation of a
cavity beneath the slab. Before drilling into the
slab, utility pipes and conduits should be noted
from the plans and confirmed to avoid drilling
through them. Recommended concrete drill
types are discussed in Appendix A.
Alternatively, core drilling companies can be
hired to drill this type of hole. If a school
district anticipates mitigating a large number of
schools using SSD, they should consider
purchasing a drill. Worker protection should
include respirators and eye protection, in
addition to ventilation of the work area to
dilute radon that is released by opening up the
subslab.
An open hole or cavity, as seen in Figure 1,
should be excavated beneath the slab with a
diameter of approximately 3-feet and a depth of
about 1-foot Experience has shown that when
1-foot diameter cavities have been enlarged to
19
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2- to 3-feet and the depth increased to 1-foot,
the negative pressure fields have often doubled
because of the decreased resistance. Although
performance improvements have been variable,
this larger cavity size has proven most
worthwhile in nonporous soils (where the most
improvement is sought). Aggregate can
sometimes be removed from the subslab either
by hand or with a powerful shop vacuum. If
the aggregate is packed tightly, a crowbar and
hand excavation may be necessary. Large
subslab cavities may require opening up a larger
slab hole just for aggregate removal. This hole
will have to be resealed with concrete.
The exhaust pipe should be well supported so
that it will not be knocked loose if it is jostled.
In school environments it is advisable to enclose
the pipe for both security and aesthetics.
5.3.4 Fan Installation
The EPA recommends that SSD fans be
installed outside the building because of the
chance of leakage of highly concentrated radon
from the fan or the pipe exhausting from the
fan into the building interior (since the fan and
exhaust pipe are under positive pressure).
Figure 1 shows two possible fan mounts. In
houses the fans are usually placed in attics, but
in schools they have been placed on the roof or
on the upper sidewall of the building exterior.
(See Appendix A for a discussion of SSD fan
installation variations.) Wall penetrations are
usually preferable because roof penetrations may
lead to roof leaks. Several fan configurations
are possible: in-line mounts that couple to
pipes, pedestal mounts with a vertical discharge,
and pedestal mounts with a horizontal
discharge. However, the piping configuration
and fan placement must be guided by building
codes in addition to practical considerations.
The system should exhaust above the roofline to
prevent high concentrations of radon from
re-entering the building. A location should be
chosen which provides a reasonable distance
between the discharge point and HVAC
fresh-air intakes, windows, doors, or any other
openings to the building interior.
5.3.5 Sealing of Radon Entry Routes
To enhance the performance of the SSD system,
an effort should be made to seal as many radon
entry routes as possible. This increases the
strength and extent of the negative pressure
- field and also reduces the amount of treated
indoor air that will be drawn into the SSD
system. Entry routes that should be sealed
include cracks in the slab and walls, the
floor/wall joint, the surface of porous concrete
block walls, and openings around utility
penetrations. Fibrous expansion joints, that are
commonly used when the slabs are poured, can
also serve as radon entry routes. These and all
other cracks and porous surfaces should be
properly prepared and sealed with a suitable
sealant.
5.3.6 Troubleshooting
Troubleshooting SSD systems may involve
taking a number of diagnostic measurements. If
radon levels are not adequately reduced, the
suction in the subslab cavity should be
measured. Law pressure may indicate high air
flow or poor fan performance; high pressure
indicates poor subslab permeability or low air
flow. The air flow in the pipe may have to be
measured to determine whether the fan is
operating properly. The pressure field extension
can be measured at various distances from the
suction hole(s) to determine the coverage of the
SSD system.
53.7 Improving System Performance
Some causes of insufficient subslab pressure
field development include: poor subslab •
permeability, the presence of subslab barriers,
competing pressures from subslab return-air
ductwork, and air leaks into the system (either
air-supply ductwork or from cracks or
openings). If the performance of an SSD
system is not adequate, a number of different
steps can be attempted to improve system
effectiveness. These include:
Additional suction points can be
installed to increase coverage area.
(This approach is most suitable when
20
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communication is poor or pressure and
flow are low.)
Larger pipe diameters, larger fans, and
larger subslab cavities have been shown
to improve SSD system performance in
some cases. (A larger fan and pipe
diameter are most appropriate when the
pressure is low and the flow is high.)
Sealing of cracks and holes can also
improve the negative pressure field
extension and, consequently, radon
reduction. Sealing will also help to
reduce the energy penalty associated
with the increased exhaust of indoor air
into the SSD system.
Reductions in room depressurizatipn (if
applicable) may also improve radon
mitigation.
Finally, it is possible that the suction
point has been located in a spot with
such poor permeability that major
improvements can only be made by
abandoning the current hole and drilling
a new hole in an area with better
permeability.
5.3.8 System Maintenance and Monitoring
One of the chief advantages of SSD systems is
that there is relatively little maintenance
required for their operation, and the fans have
long lives. Periodic system inspection and
annual retesting of the radon levels may be
sufficient if fans with an expected service life of
10-20 years are installed.
The SSD system pressure levels could be
checked and all measurements recorded
routinely, as is done with the inspection of fire
extinguishers. A pressure gauge is the most
common type of monitoring device that is used
to evaluate the continued performance of a SSD
system. Typically a dial pressure gauge (about
$50) is used to monitor the subslab cavity or
suction pipe pressure. The gauge is usually
mounted on or near the suction pipe where it
can be checked to determine if the suction
pressure is adequate. Other devices that
contain pressure switches to turn on a light or
sound an alarm if the pressure falls below a
given value are also available and are the
preferred method.
Each SSD system should be labeled with its
installation date, nominal subslab cavity or pipe
pressure depending on monitoring system, and
the name and telephone number of the persons
to contact .in case of failure. Once the final
system is installed, post-mitigation radon levels
should be monitored annually (during cold
weather) to ensure that the system is operating
effectively.
21
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6. OTHER APPROACHES TO RADON REDUCTION
Other mitigation approaches, in addition to
SSD, have been used in some schools. These
approaches may be implemented either as a
temporary solution prior to installation of a
permanent SSD system, or they be considered as
the first phase of a more extensive mitigation
plan. In some cases, implementation of these
approaches alone may adequately reduce radon
levels in the school. After confirming adequate
reductions with short-term tests, follow up with
long-term measurements to ensure that the
system continues to maintain an adequate level
of radon reduction.
Classroom pressurization, increasing ventilation,
and crawl space depressurization are discussed
below. It should be emphasized that these
approaches have not yet been thoroughly
researched by the EPA in school applications,
and more definitive guidance will be published
following additional research. Other mitigation
techniques, such as extensive sealing and
submembrane depressurization (SMD) in a
crawl space will also require extensive testing.
For technical details on how these techniques
have been used in house mitigation, refer to the
manuals on radon reduction listed in Section
1.2.
6.1 CLASSROOM PRESSURIZATION
Maintaining a positive pressure in the building
(relative to the subslab area) through HVAC
system operation has been used successfully for
temporary mitigation in a limited number of
schools. Whether pressurization is a feasible
long-term mitigation solution depends upon
factors such as the proper operation of the
HVAC system by maintenance personnel,
performance with changing climatic conditions,
and any additional maintenance costs and energy
penalties associated with the changes in
operation of the HVAC system. Any HVAC
modifications should be made in cooperation
with a qualified HVAC system specialist
Since central HVAC systems are normally
designed to operate in a forced supply mode,
the occupied spaces may be maintained under a
slight positive pressure (relative to the
outdoors) depending on the balance between
the supply and the exhaust in the building.
These systems should be checked periodically
for proper operation to ensure that a positive
pressure is maintained, and adjustments should
be made as necessary. HVAC modifications
that reduce fresh air intake, reduce supply air,
or increase return air in a given area, and
improper system maintenance can lead to
pressure imbalances, and, consequently increase
radon entry.
If positive pressures are not being achieved in a
single-fan system, the system should be checked
to ensure that the fresh-air intake meets design
specifications and that the intake has not been
closed or restricted. Increasing the fresh-air
intake and operating the fans for a sufficient
time prior to occupancy and continuously while
the school is occupied will help to reduce radon
levels that accumulate during night or weekend
setback periods. This approach will maintain
low levels during occupied hours by maintaining
a positive pressure to prevent radon entry and
providing fresh (dilution) air.
In dual-fan systems, the return-air fan can be set
back or restricted so that all the rooms are
under a positive pressure with only the supply
fan operating. The fresh-air intake to the
supply fan can also be increased up to the
design limit of the system. Another option
might be to consult with a HVAC engineer to
redesign a fresh-air intake or to add one to a
system. Diagnostic measurements made with
continuous radon monitoring equipment in each
classroom with elevated radon levels can help to
determine the necessary fan operation schedule
in such situations.
In schools with unit ventilators, increasing the
fresh-air intake to the design limit and
operating the fans continuously while the school
is occupied will help to maintain a positive
pressure in the building. A central exhaust-only
ventilation system used in conjunction with
unit ventilators or fan coil heaters might need
to be modified or replaced with a system that
operates under a slight positive pressure. For
23
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schools with no-active ventilation systems or
exhaust-only fan systems, positive pressurization
will probably require major modifications, such
as addition of a fresh-air supply, as part of a
HVAC strategy. For more detail on classroom
pressurization and how it would apply to a
specific type of HVAC system refer to Section
4.2.
If these modifications to HVAC system
operation are to be feasible long-term
mitigation approaches in a given school, then
proper operation and maintenance of the system
is critical. Performance during various climatic
conditions and any additional maintenance costs
and energy penalties associated with the changes
in operation of the HVAC system must also be
carefully considered. In addition, there may be
potential moisture and condensation problems if
pressurization is implemented in very cold
climates. The applicability of this approach will
need to be determined by qualified personnel on
a case-by-case basis. Changes made in HVAC
system design and/or operation should not
reduce the ventilation rate below the minimum
standards in ASHRAE guidelines. In addition,
any changes in HVAC controls should be
documented, labeled, and checked regularly.
6.2
INCREASING VENTILATION
Increasing ventilation by simply opening
windows, doors, or vents may be effective, but
weather, security problems, the lack of operable
windows, and increased energy costs often make
this impractical as a permanent approach in
most schools. If the windows cannot be opened
at night, it rnay be desirable to use a fan to
blow fresh air into the building to lower the
radon levels in the morning when the school is
opened. Although this approach has been
shown to reduce radon levels in some houses,
its applicability to schools has not yet been
studied. Therefore, ventilation should only be
considered as a temporary approach to radon
reduction until further research identifies its
limitations.
If an increase in ventilation is attempted, crawl
spaces and unoccupied basements can sometimes
be sealed off from the rest of the building and
treated separately. By treating these spaces
separately, ventilation reductions can be
achieved in adjacent classrooms with smaller
fresh air requirements and reduced energy
penalty. However, the practicality of this
approach in most climates will be limited due to
increased heating and/or cooling costs.
For reducing the energy costs associated with an
increase in ventilation, a heat recovery ventilator
(HRV) may be cost-effective. HRVs allow fresh
air to be delivered indoors with reduced heating
or cooling costs (depending on season) as
compared to natural ventilation. Through a
heat exchanger core, heat is transferred between
exhaust and fresh air streams, without mixing
the two airstreams. However, for an HRV to
be a reasonable mitigation option, the savings
resulting from the reduced energy penalty
should more than offset the initial cost of the
HRV.
63 CRAWL SPACE DEPRESSURIZATION
In a variation of crawl space ventilation, an
exhaust fan is installed in a crawl space vent
and all other vents are closed. This is referred
to as crawl space depressurization or forced-air
exhaust of the crawl space and can prevent
radon entry into the building Interior by
creating a pressure barrier across the floor. In
houses, this approach has been more effective in
reducing radon levels than passive crawl space
ventilation. Experience with crawl space
depressurization in schools is limited.
A diagnostic fan door test will indicate the
suitability of a crawl space for this mitigation
technique. A fan-door (e.g., blower door) will
measure the leakiness of the space and will help
to indicate the size of fan needed to adequately
depressurize the crawl space. If radon
measurements show that the crawl space is the
primary source of the problem, and if asbestos
is not present in the crawl space, then this
technique may be feasible for reducing indoor
radon levels. More detailed guidance on this
approach for schools will be available following
further research.
24
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7. SPECIAL CONSIDERATIONS
7.1.
BUILDING CODES
Building codes are typically written to reflect
minimum design and construction techniques
that must be adhered to by the construction
industry. They are developed to ensure the
public safety, health, and welfare. Building
codes are not only directed toward new
construction but also apply to renovation of
existing structures. They can be developed by
the national model code organizations or by
local jurisdictions. In general, the model codes
published by such organizations as Building
Officials and Code Administrators International
(BOCA), International Conference of Building
Officials (ICBO), and the Southern Building
Code Congress International (SBCCI) are
adopted by state or local jurisdictions or serve
as the basis for locally amended building codes.
It is important that the installer take into
account all applicable codes and laws regarding
qualifications for design and type of equipment
used when designing and installing radon
mitigation systems in any building. Typically,
this may include electrical, mechanical, fire
protection, plumbing, and building codes.
However, since these codes can vary between
different areas, the applicable codes for a given
locality should be referred to when retrofitting a
school with a radon mitigation system. It is
anticipated that specific additions or
amendments to these codes will be made in the
future to address both retrofit of school
buildings for radon reduction and radon
preventative new construction.
7.2
WORKER PROTECTION
consideration for all school administrators.
Normal safety precautions must be observed
when performing any type of construction or
remodeling work. Exposure to radon gas and
its decay products creates an additional health
risk. Therefore, it is important to reduce that
exposure as much as possible. Specifically, this
may mean increasing ventilation in the work
area and/or utilizing respirators in areas where
the radon concentration is elevated. Attention
should also be given to other potential hazards,
such as organic solvents in sealants and coatings
and potential biological hazards growing in
crawl spaces or HVAC systems.
Before drilling into the slab, utility pipes and
conduits should be noted from the plans and
confirmed to avoid drilling through them.
(However, it should be mentioned that subslab
plumbing and conduit are sometimes located,
where the installer finds it convenient and do
not always conform to the plans.) One
suggestion for avoiding an electrical shock in
this situation is to ground the case of the drill.
If the tool itself is properly grounded, it will
prevent the tool from becoming "hot" and
should cause the breaker to disconnect the
conduit that was hit. Shutting off the supply to
the drill will stop the drill but will not shut off
the subslab conduit that was hit unless they
happen to be on the same breaker.
7.3
ASBESTOS
Worker protection during radon mitigation
system installation is a legal, safety, and ethical
Any potential airborne asbestos fibers identified
in a basement, crawl space, utility tunnel, boiler
room, or any other part of the school that may
be entered as part of radon diagnostics or
mitigation should be removed or encapsulated
according to AHERA before attempting any
radon reduction activities.
25
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REFERENCES
1. ASHRAE Draft Standard 62-1981R. Ventilation for Acceptable Indoor Air Quality. ASHRAE,
Atlanta, Georgia, 1986.
2. Leovic, K. W., Craig, A B. and Saum, D. The Influences of HVAC Design and Operation on
Radon Mitigation of Existing School Buildings, presented at ASHRAE Conference IAQ 89,
April 1989.
3. Leovic, K. W., Craig, A B. and Saum, D. Characteristics of Schools With Elevated Radon
Levels, In: Proceeding: The 1988 Symposium on Radon and Radon Reduction Technology,
Volume 1, EPA-600/9-89-006a (NTIS PB 89-167480), March 1989.
4. McKelvey, W. R, Radon Remediation of Pennsylvania School Administration Building, In:
Proceedings: The 1988 Symposium on Radon and Radon Reduction Technology, Volume 2,
EPA-600/9-89-006b (NTIS PB 89-167498), March 1989.
5. Messing, M. and Saum, D. West Springfield Elementary School Report on Diagnostic Analysis
for Radon Remediation on The South Wing, Infiltec, Falls Church, Virginia, 1987.
6. Messing, M. and Saum, D. Worker Protection for Radon Mitigators and Diagnosticians, In:
Proceedings: The 1988 Symposium on Radon and Radon Reduction Technology, Volume 2,
EPA-600/9-89-006b (NTIS PB 89-167498), March 1989.
7. Saum, D. and Messing, M. Guaranteed Radon Remediation Through Simplified Diagnostics, In:
Proceedings: The Radon Diagnostics Workshop, April 13-14. 1987, EPA-600/9-89-057, June 1989.
8. Saum, D., Craig, A B. and Leovic, K.W. Radon Reduction Systems in Schools, In: Proceedings:
The 1988 Symposium on Radon and Radon Reduction in Technology, Volume 1, EPA-600/9-89-
006a (NTIS PD 89-167480), March 1989.
9. Witter (Leovic), K., Craig, A B. and Saum, D. New-Construction Techniques and HVAC
Overpressurization for Radon Reduction in Schools, Proceedings of the ASHRAE Conference
IAQ 88, 1988.
27
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APPENDIX A: TECHNICAL INFORMATION
A.1 USING CONSTRUCTION
DOCUMENTS
The term "constriction documents" refers to the
formally agreed upon construction drawings and
specifications (project manual), as well as all
subsequent addenda and change orders. The
documents are a complete pictorial depiction of
the project and consist of the architectural,
structural, mechanical, and electrical drawings.
The specifications include the bidding
documents, the conditions of the contract, and
the technical information that outlines materials
and workmanship for the entire project
Both the specifications manual and the drawings
should be obtained to aid in the understanding
of the building's radon problem. Each of these
will provide useful information. Table A.1
summarizes the information provided in these
documents.
A.1.1 Specifications
The specifications will primarily aid the
mitigator in identifying subslab aggregate
composition and soil compaction requirements.
Both of these are usually found in the section
detailing concrete work and/or fill (typically
Division 3 - Concrete). The mechanical section
(Division 15) summarizes the heating,
ventilating, and air-conditioning (HVAC)
systems applicable to the building. This section
will give details on the mechanical equipment
and offer design information that may or may
not be found on the drawings. The electrical
section (Division 16) summarizes the electrical
system.
Note: The specifications have
precedence over the drawings if there
are contradictions. For instance, it is
unlikely that aggregate was provided if
Table A.1 Radon Mitigation Information In Construction Documents
Document Information
Specifications:
Concrete (Division 3)
Mechanical (Division IS)
Electrical (Division 16)
Drawings:
Architectural
Structural
Mechanical
Electrical
Subslab composition; aggregate identification
HVAC system summary; equipment identification
Electrical system summary, equipment identification
Typical wall sections
Foundation plan; footing locations and communication
barriers, subslab fill and material thickness
HVAC system design; including duct system design, duct run
length; supply/return flow design; fresh-air introduction;
exhaust systems
Electrical equipment design and location; conduit location
29
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the specifications do not call for it, even
if the drawings show aggregate under
the slab.
A. 1.2 Drawings
The drawings provide a wealth of information
that may be useful for radon mitigation. The
architectural drawings usually show a typical
wall section. Subslab fill information is usually
shown and labeled on this section. The
structural drawings include a foundation plan
which locates footings of load-bearing walls and
columns. This is useful when identifying
potential barriers to subslab. The mechanical
drawings should include all plumbing and
HVAC drawings. Supply and return duct runs
show the amount of supply and return air flow
serving a room or area. By simply adding
together all of the flows, it can be determined if
the room was designed to be under positive or
negative pressure. Most sophisticated HVAC
systems are designed to be balanced or
pressurized in most, if not all, rooms. The
drawings should note whether or not fresh air is
introduced into the mechanical system and if
room air is removed by exhaust fans.
The electrical drawings should be consulted to
ensure that no unusual conduit routes (e.g.,
under the slab) are present in areas where the
slab may be drilled (either for placement of
suction points or for communication testing).
A.2 FAN AND PIPE SELECTION
SSD systems in houses and schools require fans
that are quiet, long-lived, energy efficient,
resistant to moisture, and that have good air
flow at pressures around 1 inch WC A number
of centrifugal duct fans manufactured by various
companies have the performance characteristics
required for most radon mitigation with an
expected service life of 10 to 20 years. Fans
that utilize the vane-axial fan blade which
surrounds the motor can be mounted in a
variety of enclosures. Specifications of some
typical in-line and pedestal fans used in radon
mitigation are shown in Table A.2.
The in-line fans are designed to be mounted
between two sections of pipe. The fan and pipe
are usually coupled with the black rubber pipe
couplings fitted with stainless steel hose clamps
that are used for plumbing pipe connections.
These couplings are available in a wide variety
of sizes so that pipes and fans of various sizes
can be coupled. Pedestal fans are designed to be
mounted on a square base that can be
constructed of pressure-treated wood. This base
is attached.over a pipe penetration on a roof or
a wall, and the fan is screwed onto and sealed
to the base.
In houses, mitigators often attempt to install the
smallest, quietest, least obtrusive, lowest power
SSD system possible. Pipes are generally 4
inches in diameter or smaller; fans are rated
generally less than 100 watts power consumption
and move less than 150 cfm air at 0.75-inch WC
pressure. In schools, however, the
considerations of noise, energy loss, and size are
not as important. Larger fans and pipes should
be considered if they produce simpler and more
effective mitigation. It is recommended that
fire-rated PVC piping, Schedule 40 PVC as a
minimum, be used.
Mitigation experience in schools, although
limited, has shown that it is advisable to use
fans that are at least twice as large (200 W and
300 cfm at 1-inch WC pressure) and pipes that
are 6-inches in diameter. The higher air flow
requires larger pipe diameters so that the
increased fan capacity is not lost in pipe
resistance. For example, these larger pipes can
be used to provide a low restriction manifold to
the fan that is connected to two vertical 4-inch
pipes penetrating the slab. The 6-inch pipe can
carry 300 cfm to the fan while each of the two
4-inch pipes carries about 150 cfm. If the larger
fans are attached directly to 4-inch pipes, then a
large part of the increased fan performance will
be lost to flow resistance of the pipe. In
summary, the larger slab areas found in schools
normally require larger fans and pipes for the
most effective SSD installations.
Table A3 shows the flow resistance for 100-feet
of pipe with diameters from 2- to 6-inches. The
length of pipe that would produce the
equivalent resistance of a system that contains
pipe, pipe fittings, and subslab flow resistance is
assumed to be about 100-feet, although typical
30
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Table A.2 Typical Fans Used for Radon Mitigation
Fan
Type
In-line
In-line
In-line
In-line
In-line
In-line
In-line
In-line
In-line
In-line
In-line
In-line
Pedestal
Pedestal
Pedestal
Pedestal
Pedestal
Pedestal
" Pedestal
Elec
Power
(W)
40
40
40
90
80
110
110
160
160
200
280
250
90
90
90
120
150
150
175
Noise
Level
(sones)
2.1
2.1
2.1
2.8
2.8
3.2
3.2
4.5
4.5
4.5
5.6
5.6
2.7
na
na
na
na
na
na
Flow*
(cfm)
25
45
45
140
140
180
180
310
310
456
470
470
75
90
110
200
200
300
530
Press. Max
@No Flow
(in. WC)
0.8
0.7
1.0
1.7
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.5
0.7
1.4
1.4
1.6
2.4**
2.8"
1.5
Width
Max.
(in.)
8.00
8.00
8.00
11.50
11.50
13.25
13.25
13.25
13.25
16.00
16.00
13.25
na
12^0
14.00
16.00
12,50
16.00
16.50
Pipe
Diam.
(in.)
4.0
5.0
5.0
6.0
6.0
8.0
8.0
8.0
8.0
12.0
12.5
10.0
na
na
na
na
na
na
na
Pipe
Length
(in.)
8.50
8.60
7.50
9.05
7.50
8.25
9.37
9.37
8.25
12.60
10.25
9.64
na
8.00
10.00
12.50
8.00
12.50
13.00
* flow measured at 0.75 inch WC pressure
** INFILTEC measured value
Table A3 Air Flow Resistance in 100 Feet of Round Pipe
Flow
(din)
10
15
25
50
100
200
300
400
500
2-in. Pipe
(in. WC)
034
0.72*
1.80
630
22.00
78.00
164.00
276.00
414.00
3 in. Pipe
(in. WC)
0,04
0.08
0.24
0.83*
2.90
1030
21.60
36.40
55.40
4 in. Pipe
(in. WC)
0.01
0.02
0.06
0.20
0.69*
2.40
5.10
8.60
13.00
6 in. Pipe
(in. WC)
0.001
0.002
0.007
0.030
0.090
0300
0.670*
1.100
1.700
These values show the approximate flows for each pipe
for which the resistance is closest to 0.75-inch WC
31
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mitigation systems usually do not have pipe runs
of more than 40-feet. For example, if a
particular fan draws 310 cfm at 0.75-inch WC
and 100 feet of 4-inch pipe has a resistance
close to 5.1-inches WC at a flow of 300 cfm, it
would be advisable to use 6-inch pipe to avoid.
wasting most of the fan power on pipe
resistance. However, large pipe is unnecessary
if little or no subslab air flow due to low
subslab permeability. Pressure drops caused by
bends (e.g., elbows) in the pipes should also be
considered when designing the SSD piping
system.
A3 DIAGNOSTIC MEASUREMENT
TOOLS
Several types of tools" are useful in gathering
diagnostic data in schools. They include an
electric-pneumatic hammer drill, a large shop
vacuum, a continuous or grab-sample radon
monitor, a sensitive pressure measurement
device, an air-flow indicator, and an air-flow
meter.
Depending on the number of schools to be
mitigated in a given district, it may be
cost-effective to purchase some of this
equipment or it may be more practical to
employ the services of an experienced radon
mitigator. It may be possible to purchase some
of this equipment from experienced mitigators
in the area or they may be able to recommend a
local source for purchase or rental of radon
mitigation supplies.
A3.1 Small Hammer Drill
Drills capable of drilling holes through concrete
slabs of at least 3/8- to 1-inch in diameter are
useful for subslab pressure, communication, and
radon measurements. The suction hole should
be 1-inch or larger in diameter, and the
communication test holes are usually 1/4- to 3/8-
inch in diameter. The inexpensive hammer
drills sold in hardware stores are often
incapable of drilling through concrete which has
hard aggregate embedded in it Professional
quality, lightweight hammer drills with spline
bits are recommended. This type of drill costs
approximately S250.
A.3.2 Vacuum
Most of the shop-type vacuum systems can draw
a vacuum of 60- to 120-inches WC and have a
maximum air flow of about 100 cfm: This is
quite adequate for inducing flow through drilled
holes approximately 1 1/2-inches in diameter for
communication tests. These vacuums are
available for $40 to S250.
A.3.3 Continuous Radon Monitor
Continuous radon monitoring (typically
averaging at 1-hour intervals) is very useful in
evaluating the effects of HVAC interactions on
school radon levels. Pylon, Femto Tech, and At
Ease are types of continuous monitors
commonly used. A number of school systems
have purchased continuous radon monitors to
aid in their school mitigation work. A
continuous monitor allows each stage to be
evaluated quickly when mitigation is performed
in stages or a number of rooms need to be
measured.
A.3.4 Grab-Sample Radon Monitor
In order to map sub-slab radon, a radon
monitor is needed that can pump a sample into
its measurement chamber and hold it long
enough for a measurement. It is very
convenient to use a Pylon AB-5 monitor which
has a built-in pump and scintillation counter
although a separate pump, Lucas cell, and
scintillation counter can be used. This
instrument can be used to take grab samples
from holes for subsequent counting, or it can be
used for continuously "sniffing" from a series of
holes. The Pylon system costs about $4500.
A.3.5 Pressure Gauge
A sensitive pressure gauge is necessary to
measure the pressure fields generated by SSD
systems. Pressure differentials as low as 0.001-
inch WC are common. The most sensitive
Dwyer Magnahelic pressure gauge, which costs
about $50, is sensitive only to about 0.01-inch
WC The slant-tube manometer is difficult to
read, to set up, and to transport It costs about
$100 and has a sensitivity of about 0.001-inch
WC The best type of pressure gauge for these
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measurements is the electronic digital
micromanometer which can read from 0.001- to
20-inches WC These micromanometers cost
about $1500.
A3.6 Air-Flow Indicators
The direction of pressure or air flow in a test
hole can provide an indication of system
performance even if it cannot be measured.
Smoke pencils or guns are most commonly used
as flow or pressure indicators. The smoke is
generated by a chemical reaction with the
moisture in the air and has an acrid odor
because of its high acid content Chemical
smoke is used because it is not associated with
heat; therefore, it will respond more accurately
to minimal air flows. The smoke pencils cost
about S3 to $4 each and can last a couple of
hours if they are used carefully. A refutable
smoke gun is also available for about S70.
A.3.7 Air-Flow Meters
Measuring air flow through HVAC registers
requires a "flow hood" which costs from $1500
to $4000. These devices are most commonly
used to balance air flows in large buildings. For
air flow measurements in ducts or pipes, a Pitot
tube (about $20) can be used in conjunction
with a sensitive pressure gauge. Alternatively, a
hot wire or hot film anemometer, costing about
$700 to $1,500, can be used. Pinwheel
anemometers, vortex shedders, and mass flow
sensors are examples of other air-flow meters
that can also be used.
A.4 INSTALLATION TOOLS
Most of the tools used for installing radon
mitigation systems are conventional tools used
by home improvement contractors. The only
specialized tool that may be required is a drill
to cut 4- to 6-inch holes through the concrete
floor slab. The following options are available:
Use a large rotary hammer drill, costing
about $400, which has a chisel action
and regular drill bits. Experience shows
that in about 20 minutes this drill can
make a large hole by drilling a circular
pattern of smaller holes and punching
the core out with the chisel.
Use a hammer drill with a carbide core
bit. The carbide core bits are expensive
(as much as $800) and may not be
available for your drill in larger size
diameters. They can drill a neat hole in
about 10 minutes.
Use a core drill with diamond bits and
water cooling. This equipment costs as
much as $2000 and is verytheavy and
bulky. However, it is the fastest way to
drill precise holes in concrete.
All of these tools can usually be rented from
tool rental shops. It may be economical to hire
a core drilling company to come to your
location with a diamond core drill if you have a
number of holes to drill.
AS SCHOOL SSD INSTALLATION
VARIATIONS
All SSD installations should have the exhaust
pipe exiting the building shell. The fan should
be mounted on the pipe outside the building
shell to avoid leakage of the radon-laden air
from cracks in the fan or from the exhaust end
pipe which is under positive pressure. EPA
recommends that the system exhaust point be
installed above roof level and be situated to
avoid any possible human exposure to high
radon levels from the SSD vented soil gas. For
any type of ran mount, extreme care should be
taken to prevent high concentrations of radon
from re-entering the building through HVAC
fresh-air intakes, windows, doors, or any other
openings to the building interior. Following
are the types of installations, and their
advantages and disadvantages, which have been
used in schools.
A5.1 Pedestal Fan on Roof
In this type of installation the pipe penetrates
the roof and connects to a pedestal fan.
Disadvantages of this type of installation are the
need to construct and seal a pedestal on the
roof for the fan to be mounted on and the need
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to cut a hole in the root (This may lead to
roof leaks or may invalidate warranties on the
roof.) Advantages are a vertical pipe run
without high resistance bends, and the low
visibility (aesthetics) of the installation.
A.5.2 In-Line Fan on Side Wall
In this type of installation the pipe penetrates
the side wall and an in-line fan is mounted
vertically on the pipe. Disadvantages of this
type of installation are the necessity of securing
the fan and ihe pipe and the potential for
damage or injury if someone climbs the pipe.
Advantages are the ease in venting above the
roof line and the fact that the roof is not
penetrated.
A.5.3 Pedestal Fan on Side Wall
In this type of installation the pipe penetrates
the side wall and discharges horizontally with a
pedestal fan mounted on the wall. A significant
disadvantage of this type of installation is the
possibility of someone coming into contact with
the discharge if the fan is not mounted high
enough or radon from the discharge leaking
back into the building through HVAC fresh-air
intakes, windows, doors, or any other openings
to the building interior. An advantage is the
lack of roof penetration.
A.5.4 In-Line Fan Above Suspended Ceiling
In this type of installation the pipe penetrates
the roof and connects to a fan which is
mounted inside the building above the
suspended ceiling. This is generally not
acceptable because of possible leakage from the
fan or exit pipe inside the building. Any radon
leakage could be distributed throughout the
building if the area above the suspended ceiling
is a return plenum for the HVAC system.
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APPENDIX B: SCHOOL MITIGATION CASE STUDIES
These case studies illustrate the staged approach
that characterizes many radon mitigation
projects in large buildings and complex houses.
Instead of trying to solve the radon problem in
an initial step, most of these projects consisted
of multiple stages where one solution was
attempted and then the results were evaluated
before initiating the next stage. The case
studies show examples of the step-by-step
procedure for radon reduction in schools. Some
of these projects (Schools A, B, C, D, E, F, G,
and H) were previously documented in the
technical paper "Radon Reduction Systems in
Schools" (Saum, Craig, and Leovic).
School A; Prince George's County. MD
This school had a sophisticated dual-fan HVAC
system that produced unbalanced flow and
exacerbated a radon problem in several rooms.
Sealing of cracks and replacement of the HVAC
fan were tried without much effect on the radon
levels. SSD systems will be installed in the
rooms with the highest radon levels since the
problem of room depressurization could not be
readily eliminated.
A.1 School Description
The school building, which was built in 1969, is
two-story, slab-on-grade construction. It uses a
large dual-fan air handling system for HVAC
Each room has separate supply and return
louvered vents in the suspended ceiling. The
HVAC system is designed to operate
continuously during occupied hours and to
provide positive pressurization in all rooms.
A.2 Initial Radon Tests
Radon levels in this school were initially
measured in February 1988. One classroom
tested above 40 pCi/L, a teachers' lounge tested
above 20 pCi/L, and several other classrooms
tested between 4 and 20 pCi/L.
A3 Building Plan Inspection
The foundation drawings call for a 4-inch gravel
bed and a 6-mil plastic vapor barrier under a
4-inch slab. A %-inch expansion joint runs
across the entire building. The footings run
below virtually all interior and exterior walls.
Square footings support columns.
The HVAC system fans have a rated capacity of
51,000 cfm of air supply and 34,000 cfm of
return air. This would result in positive
pressure in all rooms if the system were
properly balanced.
A4 Walk-Through Building Inspection
Examination of the air-handling system showed
that the air supply fan had been damaged and
part of the housing cut away; this resulted in a
great loss of capacity. It was determined that
the distribution fan was actually supplying less
air than the return air fan was removing; this
resulted in a negative pressure in many rooms.
The room with the highest radon level had the
greatest negative pressure and also had a very
large floor-to-wall crack along one wall. This
particular floor-to-wall crack was an expansion
joint where two parts of the building were
joined. The expansion joint had disintegrated
and the two building sections appeared to have
separated an additional it-inch, leaving a full
1-inch gap between the floor and wall. This gap
was concealed by an aluminum angle iron
installed when the building was built. The
expansion joint and the angle iron continued
vertically up both corners so that they were
serving as an expansion/contraction joint
between the two parts of the building.
AS Pre-Mitigation Diagnostics
Pressure measurements indicated that many of
the rooms were under negative pressure when
both the supply and return fans were in
operation. The room with the highest radon
level measured 0.060-inch WC negative pressure
(relative to the subslab). There was a good
correlation between negative pressure and radon
levels in all rooms, with the highest radon levels
in the rooms with the highest negative
pressures. All rooms in the school with any
amount of positive pressure had low radon
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levels. Subslab radon levels were about 500
pCi/L in all rooms. When the return air fan
was turned off, the pressure in all rooms
became positive and radon levels decreased to
less than 2 pCi/L.
A.6 Temporary Mitigation
As a temporary solution to reduce radon levels,
the return air fan was left off and the HVAC
system operated with only the air distribution
fan. Under these conditions all rooms showed
positive pressure and had radon levels below 2
pCi/L.
A.7 First-Stage Mitigation
The floor-to-wall building expansion crack was
sealed with a backer rod and polyurethane
caulking. This sealing decreased radon levels
only slightly when both fans were off, which
indicated that there were other soil gas entry
points in the room. This poor result from
sealing a major crack was surprising because
this crack was about 1-inch wide and soil gas
with 500 pCi/L flowed out of it when the
pressure was negative.
A.8 Second-Stage Mitigation
Little effect was seen on the negative pressures
in the problem rooms although the damaged
supply fan was replaced. Building personnel
have attempted to identify the cause of the flow
imbalance to these rooms. This will be further
investigated.
A.9 Third-Stage Mitigation
A decision was made to install SSD systems in
the two rooms with the highest radon levels
since an HVAC modification was not found to
solve the negative pressure problem in the
rooms. Installation of SSD systems would also
reduce radon entry when the air handlers are
not operating during night or weekend setbacks.
T3B fans were installed on 6-inch pipes in the
two rooms with the highest radon levels. The
return air grill was permanently disconnected
from the return air duct in the teacher's lounge
to alleviate the problem there. Since the lounge
is used for smoking, it is probably not a good
idea to recirculate the air. The return grill is
now directly vented to the outdoors.
Post-mitigation tests from this stage are not yet
available.
A.10 Conclusions
Although mitigation of this school is not yet
complete, SSD in this case appeared to be a
more reliable solution to the radon problem
than crack sealing or HVAC modifications.
SSD should solve the radon problem both
during the day while the HVAC system is
turned on and during the night when it is
turned off.
School B; Washington County. MD
This is an example of a school with a complex
radon problem that was mitigated in multiple
steps. A large number of SSD suction points
had to be used because of the school's complex
footing structure and poor aggregate. The
mitigation performance was evaluated by
retesting as each suction system was installed or
improved with a larger fan, larger pipe, or
larger subslab cavity. With hindsight it is clear
that some of these steps could have been
consolidated; radon mitigation is not an exact
science and it is often beneficial to try a simple
solution and evaluate the results before
continuing. In this case, the simplest solution
was installing a single suction point in the
center of the basement slab near the highest
concentrations of subslab radon. Although this
single suction point did provide considerable
radon reduction in the basement, it was
necessary to install several other suction points
around the edges of the slabs to bring the levels
well below 4 pCi/L.
B.1 School Description
This is a small school, 80 by 150 feet, built on
the side of a hill. The school has a 21 by 150
foot walk-out basement along its lower side.
The unexcavated area is slab-on-grade, with the
slab extending over the basement area and
resting on steel-bar joists. The foundation walls
are constructed of concrete blocks. The interior
walls of the basement support the end of the
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bar joists and the slab. This wall is not painted
or waterproofed on either side. Separate
single-fan, roof-mounted HVAC systems with
ceiling-mounted duct work are provided for the
basement and upstairs.
B.2 Initial Radon Tests
Charcoal canister measurements taken over a
weekend in March 1988 averaged 10.5 pCi/L in
the basement and 4.3 pCi/L on the first floor.
It is unknown how the air handlers were
operating during the test. All rooms were
retested over a weekend in May 1988 with air
handlers turned off. Measurements ranged from
78 to 82 pCi/L in the basement and from 18 to
33 pCi/L on the first floor.
B.3 Building Plan Inspection
The building plans indicate that the first floor
and unfinished basement were constructed in
1971. In 1976 the basement was converted into
classrooms and a slab-on-grade greenhouse was
added. The foundation plans show a complex
footing structure upstairs that would limit the
extent of pressure fields from SSD systems.
There are, however, basement footings at the
periphery of the slab which would allow any
basement SSD pressure fields to be limited only
by the aggregate porosity. One specification
notes that "completed fill, prior to laying of
floor slabs, shall have density and compressive
value of not less than 95% of the normal
undisturbed soil value....The fill directly under
concrete slabs on grade shall be clean crushed
limestone; 1/2 in. minimum, 1 in. maximum size
leveled, compacted to 4 in. minimum thickness
or as shown on drawings." No soil test results
are provided.
B.4 Walk-Through Building Inspection
The upstairs and downstairs are mostly open
areas subdivided by movable low partitions.
The HVAC supply and return grills are
positioned so that there are only a few offices
and storage areas where the HVAC system
could cause depressurization. No major radon
entry routes were noted other than typical small
(1/8-inch) cracks between the walls and the floor
slabs and expansion joints.
B.5 Pre-Mitigation Diagnostics
Radon mapping was conducted by drilling small
holes in the floor and walls and "sniffing" with a
continuous radon monitor. These tests resulted
in measurements of about 1500 pCi/L in the
floor and block walls around the central stair
well. Other floor and wall samples were below
SOOpCi/L.
Hourly continuous radon monitoring over
several weeks showed that radon levels were low
when the HVAC systems were operating.
During nights and weekends when the system
was in a "setback" mode, radon levels rose quite
rapidly to as high as 150 pCi/L downstairs and
80 pCi/L upstairs. Pressure measurements
through holes in the slab showed that the
HVAC systems resulted in small positive
pressures within the building that provided
complete remediation as long as they were
operating. However, the HVAC fans only
operated when heating or cooling was
demanded; during mild weather they seldom
operated. The March charcoal measurements
were made during cold weather that probably
required more HVAC operation than the May
tests which showed much higher radon levels.
Communication tests showed that a trace of
suction could be measured across 20-feet of the
center of the basement floor and in the nearby
walls. This suction confirmed that some
aggregate was present, that the permeability was
marginal, and that an SSD system might be able
to produce significant mitigation.
B.6 Temporary Mitigation
When the radon problem was discovered in
March, the students were moved out of the
basement classrooms where the levels were the
highest Tests in May showed the levels
increasing upstairs, probably because of the
diminished cycling of the HVAC system in mild
weather. For temporary mitigation, until the
school recessed for the summer, the HVAC fans
were turned on continuously both upstairs and
downstairs when the building was occupied.
Although this provided complete mitigation
under spring conditions, it was not considered
an acceptable permanent solution because of the
increased wear on the HVAC fans and the
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unknown level of performance in the winter.
Even with closed fresh-air dampers, a very slight
positive pressure which produced complete
remediation was generated in the building. If
HVAC mitigation had not been possible, one
option might have been to install a large
portable fan which would have been used to
blow air in through an open door while classes
were in session, or the school might have been
closed early for the summer.
B.7 First-Stage Mitigation
A 4-inch diameter suction hole was drilled
through the slab in a centrally located basement
closet near the highest subslab radon
measurements. The aggregate exposed by this
hole was about 4-inches deep; it contained fine
material which limited its permeability. A
1-foot diameter cavity was excavated in the
aggregate and a 4-inch diameter suction pipe
was installed across a dropped ceiling, out a
back wall on the downhill side, and vented up
above the roof line. Larger 6-inch diameter
pipe would have been installed to allow more
air flow and a bigger fan, but the clearance
above the suspended ceiling was too low. A
Kanalflakt T2 in-line fan was coupled to the
pipe to provide about 1-inch WC of suction in
the subslab cavity. After several days of
operation, a continuous radon monitor showed
a drop in the basement radon to about 40
pCi/L. These tests had to be made during the
weekend when the temporary mitigation scheme
involving the HVAC system could be
discontinued without exposing the students to
high radon levels. The upstairs levels dropped
to about 20 pCi/L. (All air-handlers were off.)
These results suggested that the SSD system had
a significant effect on the major radon source in
the building, but other sources remained to be
mitigated and/or the main source was not
completely mitigated.
B.8 Second-Stage Mitigation
In order to improve the performance of the
single suction-point system, the subslab cavity
was expanded from about 1-foot in diameter to
about 2 by 3 feet This significantly increased
the air flow as indicated by a drop in cavity
pressure from about 1- to 0.5-inch WC It also
doubled the pressure field under the slab as
indicated by the fact that the pressures in a hole
13-feet from the suction point increased from
0.012- to 0.025-inch WC Radon levels upstairs
and downstairs also decreased slightly.
B.9 Third-Stage Mitigation
In the next attempt to increase the performance
of the single point SSD system in the basement,
the fan was increased from a Kanalflakt T2 to a
T3B. This increased the suction in the cavity
from 0.5- to 0.7-inch WC which was not as large
as might be expected since the T3B is capable
of moving more than twice the air flow of the
T2 at the same pressure. The increase that was
smaller than expected in subslab pressure is
probably due to the flow restriction and
pressure loss in the 4-inch diameter pipe. A
slight decrease in radon levels was noted, but
the levels downstairs and upstairs were still
about 20 and 15 pCi/L, respectively, after the
HVAC fans were off for 24 hours.
B.10 Fourth-Stage Mitigation
Since some radon was thought to be coming
from under the first floor slab, a suction system
was installed near the woodworking shop where
the highest upstairs subslab air measurements
had been taken. A T2 fan and 4-inch pipe were
installed and a T fitting was coupled to the
pipe and sealed so that a second suction point
could be added to this system. The subslab
aggregate was found to be only 2 inches deep
and full of fine material, limiting its
permeability. Continuous radon measurements
showed very little change after the system was
turned on.
B.11 Fifth-Stage Mitigation
To improve the performance of the upstairs
system, a second suction point was installed
about 20 feet away from the first In addition,
the fan was replaced with a T3B and the pipe
near the fan was replaced with 6-inch diameter
pipe to handle the increased flow from the two
suction pipes. The initial suction point cavity
beneath the slab was increased from 1-foot in
diameter to 3 by 2 feet to increase the subslab
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air flow. A slight decrease in the upstairs radon
levels was observed.
B.12 Sixth-Stage Mitigation
In order to complete the mitigation system
downstairs, two more suction systems were
installed at the ends of the basement These
systems used 4-inch pipe and T2 fans, with
about 1-foot cavities in the aggregate beneath
the slab. In addition, all three downstairs
systems had T fittings installed in the pipe
about 6-feet above the floor, horizontal 4-inch
pipes penetrated the hollow concrete block
walls. Unfortunately, the wall suction created
so much air flow in the pipes that the subslab
cavity pressures in all the systems fell to about
0.2-inch WC, and the continuous radon monitor
in the basement showed that the net result was
a significant increase in basement radon.
B.13 Seventh-Stage Mitigation
When the wall suction pipes were cut and
sealed, the subslab cavity pressures in all the
systems rose to about 0.7-inch WC and the
basement continuous radon monitor showed
levels below 2 pCi/L. Pressure field
measurements in the basement showed
measurable depressurization under all of the
slab.
B.14 Eighth-Stage Mitigation
The upstairs radon levels were still observed to
range from 4 to 10 pCi/L, so three more subslab
suction points were installed along the uphill
side of the upstairs slab. These systems were
separated by about 30 feet and consisted of
6-inch pipe with two points manifolded to a T2
fan and a third connected to a CV9
wall-mounted fan that discharged horizontally
about 10 feet off the ground.
B.1S Ninth-Stage Mitigation
Continuous radon measurements showed that
some peaks above 4 pCi/L were associated with
the greenhouse area which had two of the three
new suction points. After the fan on these
points was increased to a T4, the radon levels
remained below 2 pCi/L.
B.16 Cost Estimates
The cost estimates given below are higher than
the actual expenses because of the research
nature of this project, but the following
breakdown may be useful:
1. Labor for SSD installations:
6 SSD Systems @ 2 person days per
system = 12 person days.
2. Parts cost for SSD installations (fans,
pipe, electrical):
6 SSD Systems @ S500 per system =
$3,000.
3. Labor for post-mitigation testing:
9 stages @ 0.5 person day for
distribution and pickup = 4.5 person
days
4. Charcoal canisters for post-mitigation
testing at each stage:
9 stages with 10 canisters each @ S10
per canister = $900
5. Pre-mitigation diagnostic work by
experienced home mitigator:
2 days @ S500 per day = $1000
6. Continuous radon monitoring by
consultant to monitor progress:
30 days @ $1007 per day = $3000
The'total is 16.5 person days of labor and
$7,900 in parts and consultant fees. Since
continuous radon monitors are available for
about $3000, it may be cost effective for school
systems with extensive radon problems to
purchase their own monitors.
B.17 Conclusion
Houses with marginal subslab porosity can often
be mitigated with SSD if enough suction points
can be installed. This school required a similar
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mitigation system. Winter testing with long
term alpha-track monitors measured below 4
pCi/L with most of the rooms measuring below
2 pCi/L. Pressure gauges were placed on most
of the suction pipes so that the fan performance
can be quickly checked.
School C; Washington County. MD
This successful school mitigation project is an
example where large SSD fans can be used to
mitigate large slab areas with 6-inch diameter
pipe used as a manifold to connect the fan to
several 4-inch diameter pipes that penetrate the
slab.
C.1 School Description
This entire school building is slab-on-grade with
block walls and no utilities below grade except
sanitary sewers. The original building was
constructed in 1956 and has four area air
handlers for heating and ventilating with a
central boiler room. A classroom wing was
added in 1968 and unit ventilators were used in
each room. No part of the building is
air-conditioned.
C2 Initial Radon Tests
Elevated radon levels were found in the locker
rooms on each side of the gymnasium in the
original building and in the new classroom wing.
The April 1988 screening tests with charcoal
canisters showed that 21 of 72 tests were above
4 pCi/L: 7 were above 8 pCi/L, and 1 was above
20 pCi/L (26.7). The highest levels were in the
new classroom wing.
C.3 Pre-Mitigation Diagnostics
Although the locker rooms and gymnasium are
on the same air handler, the gymnasium
measured 1.8 pCJ/L whereas the girls' locker
room measured 4.9 to 63 pCi/L and the boys'
locker room measured 53 to 19 pCi/L. Further
examination indicated that each locker room
area had a large exhaust fan to remove odors
and shower steam. Differential pressure
measurements (using a micromanometer), with
the air handler and exhaust fans operating,
correlated with the radon levels showing that
the gym pressure was slightly positive, the girls'
locker room area slightly negative, and the boys'
locker room area significantly negative.
In April 1988 weekend charcoal canister
measurements were made in the new classroom
wing with the unit ventilators turned off. All
rooms but one were above 4 pCi/L; a room in
the northeast corner of the building measured
26.7 pCi/L. Radon levels decreased from north
to south in this wing as did subslab radon
levels. A continuous radon monitor was placed
in the room with the highest radon levels.
When the unit ventilator was off, levels above
20 pCi/L were reached nightly but remained
below 2 pCi/L when the unit ventilator was
operating continuously. Pressure measurements
made with a micromanometer confirmed that
the unit ventilator was pressurizing the room
slightly.
C4 First-Stage Mitigation
Construction plans showed that each locker
room area was a continuous slab with aggregate
beneath it. As a result, a 6-inch subslab suction
point was placed in each of the two locker
room areas with a 1-foot diameter subslab hole
and a Kanalflakt GV-9 fan (rated at 200 cfm at
0.75 inch static pressure). Both locker room
areas measured less than 4 pCi/L with the
exhaust fans and the subslab depressurization
systems operating.
In the new wing, the unit ventilators are turned
off at night except in extremely cold weather
when they are cycled. It was decided to install
two subslab depressurization points in this wing
to provide mitigation when the unit ventilators
were not operated. The two 4-inch pipes were
installed in the hall and manifolded with an
above-ceiling 6-inch pipe running to a
Kanalflakt GV-12 fan (rated at 510 cfm at 0.75
inch static pressure) at the north end of the
building. One suction point was installed with a
3-foot diameter subslab hole about 20 feet from
the east end of the hall. The other suction
point was installed with a 1-foot diameter
subslab hole about 60 feet from the end of the
hall. Pressure field extension measurements
indicated that the two fields overlapped; all slab
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areas of the wing, except the most southern
classrooms, were depressurized to the outside
walls.
C.5 Second-Stage Mitigation
Since the new wing pressure field extension
around the 1-foot diameter suction hole was not
as great as around the 3-foot suction hole, the
1-foot subslab suction hole was increased to 3
feet in diameter. This extended the measurable
depressurization area by 10 feet to the south,
which was sufficient to reach the last two
classrooms. The amount of depressurization in
the test holes in all directions around the
suction point was doubled. With the subslab
depressurization system operating, radon levels
were below 4 pCi/L in all classrooms with the
unit ventilator fans off.
C.6
Conclusion
This school was relatively simple to mitigate
and, although the subslab communication was
not very good due to low quality aggregate, the
three SSD systems performed adequately
because of large fans, large diameter pipe, and
large subslab suction pits.
School D: Washington County. MD
This successful school mitigation showed that
schools with radiant heating coils in the slab
can be mitigated with SSD if a deep layer of
aggregate is under the slab. The project was
expected to be difficult because of the limited
number of places where the slab could be
penetrated without the danger of drilling
through a hot water pipe. A newer section of
the school, heated with unit ventilators, was
mitigated with two multi-point SSD systems.
D.I School Description
The original building of this school was built in
1958 and is heated with hot water radiant heat
in the slab. In 1978 a kindergarten room was
added in an off set to the original building, and
a separate building (Building B) was built which
contains four classrooms, a library, a teachers'
workroom, a conference room, and restrooms.
The kindergarten room is heated with hot water
radiant heat, and the new building is heated
with unit ventilators. Office space in the
original building is air-conditioned with a
window unit No other area of either building
is air-conditioned.
The original building has two 3600 cfm
roof-mounted fans that can be used to exhaust
air in plenums over the hall ceiling. Each room
has a ceiling vent which connects to these hall
plenums. However, the exhaust fans are never
used. Consequently, the building has no active
ventilation system.
D.2 Initial Radon Tests
All rooms in both buildings were tested with
charcoal canisters over a weekend in mid-April.
Of 24 tests, 21 were over 4 pCi/L, 16 were over
8 pCi/L, and 3 were over 20 pCi/L. The eight
rooms in Building B measured between 17 and
20 pCi/L. It is believed that the unit
ventilators were off during the testing weekend,
but this could not be confirmed. Seven tests in
the classrooms, library, and multi-purpose room
in the original building measured between 12
and 23 pCi/L.
D.3 Building Plan Inspection
Plans showed that the initial building and
kindergarten addition had 6 inches of aggregate
under a 6-inch thick slab containing hot water
pipes for heating. Building B had 4 inches of
aggregate under a 4-inch slab.
D.4 Pre-Mitigation Diagnostics
A continuous radon monitor was placed in one
of the classrooms in Building B to measure the
effect of unit ventilator operation on radon
entry. It was found that radon levels would rise
overnight to above 20 pCi/L with the ventilator
off but would remain below 2 pCi/L with the
ventilators operating. Again, this shows that a
unit ventilator can reduce radon levels by
pressurizing the room slightly. When run
continuously this type of unit ventilator can
prevent radon entry.
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D.S First-Stage Mitigation
Since the Building B ventilators are off during
night setback, a four-point, two-fan subslab
depressurization system was installed to reduce
radon entry. The risers are 4-inch pipes
connected to two 6-inch manifold pipes above
the dropped ceiling. (Two risers are manifolded
to each pipe.) A Kanalflakt GV-9 fan (rated at
200 cfm at 0.75-inch static pressure) is used to
exhaust each system. Pressure field extension
measurements indicated that subslab
depressurization extended 50 feet, the minimum
distance necessary to reach all parts of the slab.
With the Building B subslab system operating
and the unit ventilators off, all rooms remained
below 4 pCi/L. However, based on the
pressure field extension measurements, the
system may be of marginal value during cold
weather. If radon levels rise above 4 pCi/L it is
believed that subslab depressurization can be
improved by sealing the floor-to-wall opening.
A K-inch expansion joint around all of the slabs
in the building is deteriorating, leaving
significant openings to the subslab. This
probably leads to some short-circuiting of the
subslab depressurization system.
D.6 Second-Stage Mitigation
Subslab suction on this original building (the
intra-slab radiant-heat building) was a challenge
since construction plans showed that the hot
water pipes in the slab were separated by no
more than 15 inches over the entire building.
As a result, it was difficult to locate an area
where a 6-inch subslab suction point could be
put through the slab without running the risk of
damaging a hot water pipe. Building plans
identified a 3-foot square area without water
pipes in each room. A hole was successfully cut
through one of these areas. The plans indicated
that the aggregate was a minimum of 6 inches
deep, much deeper than at any other school
examined. A 6-inch suction point was installed
with a 3-foot diameter hole with a Kanalflakt
KTR150-8 fan (rated at 510 cfm at 0.75-inch
static pressure). Pressure field extension was far
greater than expected; depressurization could be
measured as far as 90 feet from the suction
hole. These results were surprising since the
aggregate appeared to be some type of "crusher
run" aggregate with a certain amount of fines.
However, in leveling the aggregate before
pouring the concrete, it is probable that most of
the fines had sifted to the lower portion of the
aggregate bed leaving a fairly thick area of
large-diameter aggregate immediately under the
concrete. It is believed that this layer of coarse
stone enhanced pressure field extension; this
will be studied further. It appears that this one
suction point will solve the problem in the
original building. If this one suction point is
not sufficient to treat the entire building, it may
take a second point, operated on a separate fan,
to completely mitigate the building.
Since the kindergarten room is an addition, the
subslab area does not communicate with the
original building. Consequently, a suction point
was put in a closet adjacent to a restroom
where the hot water pipes were spaced 24
inches apart to clear the commode's sewer line.
A Kanalflakt T-2 fan (rated at 140 cfm at 0.75
inch static pressure) installed on this point
lowered radon levels to below 2 pCi/L. No
pressure field extension measurements were
made for fear of damaging a heating water pipe.
This school has been retested over the winter to
determine if the SSD systems continue to
mitigate during cold weather conditions; results
should be available soon.
D.7 Conclusion
The ease of mitigating several thousand square
feet with one SSD suction point in the older
section of this school was an encouraging result.
Building B was a standard installation with two
suction points on each of two SSD systems.
School E; Fairfax County. VA
This successful school mitigation project showed
that radon problems can be aggravated by
exhaust-only ventilation systems that produce
continuous negative pressures in all rooms
(relative to the subslab area). However, it was
also shown that, with sufficient subslab
permeability, SSD systems can achieve successful
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radon mitigation under these adverse conditions
of negative pressure.
E.1 School Description
This slab-on-grade building is "L-shaped," and
each wing has a central hall with classrooms on
each side. The rooms are heated by hot water
fin heaters along the outside walls. Each room
had ceiling exhaust vents into a plenum over the
rooms and halls. Since there was no supply air
fan, the roof-mounted exhaust fans in this
plenum caused severe depressurization (0.060
inch WC negative pressure) of the entire
building, and any make-up air entered the
building only through infiltration induced by the
depressurization.
The building was designed so that each
classroom would be ventilated adequately only if
one of the windows was left open.
Unfortunately, the severe depressurization was
also drawing subslab soil gas containing radon
into the building.
E.2
Initial Radon Tests
Tests during the fall of 1987 in this school were
the first to suggest that radon levels in
classrooms varied widely from room to room,
and that the test results were difficult to predict
from room location and construction. Initially,
charcoal screening tests were conducted in a few
classrooms with the highest test showing
approximately 6 pCi/L. Subsequent tests in all
classrooms by the PTA showed several
classrooms over 20 pCi/L. The two end
classrooms of the southwest wing had levels of
22 and 17 pCi/L with three other rooms above
4 pCi/L. The southeast wing had three rooms
with moderately elevated levels of 5, 6, and 7
pCi/L.
E.3 Building Plan Inspection
The building plans and specifications called for
4 inches of aggregate under the slab. The
foundation plans showed that the slab was
thicker along the hall between the classrooms.
E.4 Temporary Mitigation
The students were moved out of the rooms with
the highest radon levels until the problem could
be corrected. Since there was little experience
with school radon mitigation in Fairfax County
at this time, it was not known how long it
would take to fix the problem.
E.S Pre-Mitigation Diagnostics
Subslab communication tests and radon tests
were performed to locate the radon sources and
to determine whether SSD was a possibility.
Radon levels from 25 to 2000 pCi/L were found
under the slab and were consistent with the
location of rooms with highest screening
measurements. The subslab communication was
found to be good, except in the thickened area
of the slab. Separate suction points would have
to be placed on each side of the hall. There
was good communication under the interior
walls that are perpendicular to the hall. This
was consistent with the foundation plans that
showed that these walls were non-load-bearing.
E.6 First-Stage Mitigation
A number of mitigation strategies were
considered, including reversal of the exhaust
fans to create pressurization, drilling ventilation
holes through the walls behind the radiators to
provide more fresh air, and replacing the entire
HVAC system with a positive pressurization
system. Before these expensive solutions were
attempted, it was decided to try the simple
techniques recommended by the EPA for house
mitigation: eliminating depressurization, sealing
cracks, and SSD. For eliminating
depressurization, the HVAC exhaust fans were
turned off and the rooms were retested to
determine if the building could be mitigated by
simply removing the negative pressure.
Surprisingly, some of the rooms were still above
10 pCi/L under these conditions. It seems that
the lower pressure probably reduced radon entry
rates, but it also reduced the entry of fresh air
that was diluting the radon.
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E.7 Second-Stage Mitigation
The rooms with the highest radon levels were
found to have cracks between the floor and wall
that varied from to % inch wide. These cracks
were carefully sealed and re-testing of the room
indicated a reduction of radon levels from 0 to
50 percent.
It is not unusual to get marginal mitigation
results from crack sealing in houses. This is
thought to be due to the difficulty in sealing all
the radon entry routes such as porous hollow
block walls. In addition, the radon levels often
build up behind effective sealants, so that any
unsealed leaks may provide more radon.
E.8 Third-Stage Mitigation
Subslab suction points were put in the two end
rooms of the southwest wing. The subslab
suction points were manifolded overhead and
connected to one Kanalflakt GD-9 fan (rated at
310 cfm at 0.75-inch static pressure). Subslab
excavation revealed that the aggregate was
present and that it did not have significant fine
material that would impede air flow. With this
SSD system in operation there was good
pressure field extension to at least three rooms
on each side of the hall. In addition, all of the
floor-to-wall joints were carefully sealed in all of
the rooms'of both wings. Following sealing and
installation of the two suction points, all of the
rooms in both wings tested below 4 pCi/L.
E.9 Fourth-Stage Mitigation
During December 1988, short-term tests
revealed that radon levels were again above 4
pCi/L (despite the previous sealing work) in the
southeast wing that did not have an SSD
installed. Although longer term tests indicated
that the long-term averages were below 4 pCi/L,
school personnel decided to install an SSD
system in this wing. This work has been
completed, and all classrooms are below 4
pCi/L.
E.10 Conclusion
Mitigation of this school showed that, since
subslab permeability was good, SSD was
applicable despite the large size and complex
ventilation system. Sealing and the reduction of
depressurization were marginally effective, but
SSD was very effective despite the
depressurization of the building by the HVAC
exhaust fans.
School F; Washington County, MD
This ongoing, initially unsuccessful school
mitigation project shows that mistakes can be
made easily in selecting an appropriate radon
mitigation method. In this case, an attempt to
use SSD to overcome subslab return air duct
leakage was a failure; a more expensive solution
will probably be necessary.
F.I Initial Radon Tests
In April 1988, 39 charcoal canister radon tests
showed that 28 were above 4 pCi/L, 8 were
above 8 pCi/L, and none were above 20 pCi/L.
All of the screening and confirmation tests were
made when the building was unoccupied and the
HVAC system was turned off.
F.2 Building Plan Inspection
The original school was built in 1954, and
additions were made in 1964. Both are
slab-on-grade construction. The additions have
an HVAC system with return air ducts that are
underneath the slab. The foundation plans and
specifications call for 4 inches of aggregate
under the slabs.
F3 Pre-Mitigation Diagnostics
Radon grab samples showed about 20 pCi/L in
the HVAC supply air when the system was
turned on. This indicated that the return air
ducts under the slab were drawing in soil gas
and recirculating it through the school. Subslab
pressure measurements indicated a pressure field
that ranged from 0.1- to 0.001-inch WC of
negative pressure. The largest pressures were
nearest the return air exhaust vent that went up
to the roof mounted fan system. These
measurements suggested that if a SSD system
were installed which would produce a larger
competing pressure under the slab, the soil gas
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could not enter the cracks in the return air
pipes.
F.4 First-Stage Mitigation
A Kanalflakt GV9 fan was mounted on the
roof, connected by a 6-inch manifold pipe to
two 4-inch diameter pipes. Suction points for
these smaller pipes were drilled though the slab
near the return exhaust stack in order to
maximize the suction where diagnostics had
indicated that the return air subslab suction was
the highest. These slab penetrations uncovered
good aggregate without excessive fine material.
However, it soon became obvious that this SSD
system could not overcome radon entry into the
return air ducts. The diagnostic measurements
of the return air pressure field had been made
through holes drilled through the slab and not
through holes drilled through the actual return
air pipe under the slab. When this pipe was
exposed through the holes drilled for the 4-inch
pipe, pressure measurements showed 0.8-inch
WC inside the pipe. The diagnostics had
confused the small subslab negative pressure
that was caused by duct leakage with the much
larger negative pressure in the pipe. It is very
unlikely that a SSD system could realistically
depressurize all areas of the slab to a level
(approximately 0.8-inch WC in this case) that
would be required to prevent soil gas from
entering any cracks in the pipe. Subsequent
radon tests indicated that the installed system
had a negligible effect on the radon levels in
the school.
F.5
Conclusion
Schools with subslab HVAC ductwork create a
major problem that may require an alternative
mitigation approach to SSD. Although it is
generally a good idea to try a simple,
inexpensive mitigation technique before trying
the more complex and expensive techniques,
there should be some experience or theory that
provides some confidence that the technique
will work.
A new overhead air-return system is now being
installed in this school, and follow up diagnostic
measurements are planned.
School G; Arlington County. VA
This successful school mitigation project showed
that schools with minor radon problems in a
few rooms may be mitigated by craclc sealing or
correction of HVAC imbalances. However, it is
unlikely that these measures would be effective
for radon levels significantly over 8 pCi/L since
reductions from these approaches are usually
about 50 percent
G.I School Description
Half of this older school building is one-story
slab-on-grade; the other half is two-story with a
walk-out basement The walls are constructed
of hollow blocks and the exterior of the school
is brick veneer. The HVAC system combines
unit ventilators with a single-fan air handling
system with overhead duct work.
G.2 Initial Radon Tests
Initial and follow-up charcoal canister tests
showed only two basement rooms between 4
and 8 pCi/L. All other rooms were below 4
pCi/L. The measurements were made during
unoccupied periods.
G3 Walk-Through Building Inspection
The HVAC supply vent in one of the problem
rooms was found to be inoperative and the
other room was found to have a 1/2-inch wide
building expansion crack that was loosely
covered by baseboard molding.
G.4 Pre-Mitigation Diagnostics
Subslab radon levels of 500 to 1000 pCi/L were
measured in the basement area. A negative
pressure in the room with the inoperative
supply vent could be detected by air movement
into the room when the HVAC fan was
operating.
G.5 First-Stage Mitigation
An HVAC contractor was called in to correct
the HVAC supply duct problem, and the
building separation crack was sealed with a
pourable polyurethane caulk. After these
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mitigation efforts were complete, continuous
radon monitoring and short-term charcoal tests
showed that the room with supply vent
problems was below 2 pCi/L, but the room with
the building separation crack still had daily
peaks above 4 pG/L. Further examination of
the slab in this room showed an additional &
inch wide and 30-foot long crack between the
floor and the wall underneath a unit ventilator
system along one wall.
G.6 Second-Stage Mitigation
The unit ventilator covers in the remaining
problem room were removed to gain access to
the crack and pourable polyurethane caulk was
used to seal it. Continuous monitoring and
charcoal canister tests showed that the radon
levels were now consistently below 4 pCi/L.
Both problem rooms will be retested over the
winter to determine if the mitigation continues
to be effective.
G.7 Conclusion
When radon levels are slightly elevated (less
than 8 pCi/L), then mitigation solutions such as
crack sealing and elimination of gross HVAC
depressurization may be effective. However, in
many cases these techniques fail to reduce radon
levels by as much as 50 percent, and the
problem may recur during the winter. Sealing
may not be very effective because many entry
routes such as porous hollow block walls are
hard to seal. Effective sealing causes a higher
concentration of radon to build up behind the
seal so that the few remaining entry routes may
leak soil gas with higher radon concentrations.
When HVAC depressurization is eliminated,
there is still a slight depressurization of the
upper surface of the slab due to the buoyancy
of wanner air in the building (natural stack •
effect). The more effective and dependable
mitigation techniques rely on positive
pressurization above the slab, or negative
pressurization beneath the slab.
School H; Washington County. MD
This ongoing school mitigation project is
attempting to mitigate a combination
crawl-space/slab-on-grade school. A large
exhaust fan has been installed in the crawl space
and the radon levels in the crawl space and the
building have been slightly reduced. Future
plans call for increased air sealing of the crawl
space, retesting of the pressure and radon levels,
evaluation of the mitigation effects of the
HVAC system, and installation of a subslab
suction system under the slab-on-grade section
of the school.
H.1 School Description
Half of this single story building is over a crawl
space and the other half is slab-on-grade. The
HVAC system is a single-fan system with
overhead duct work. The exterior of the school
is brick veneer. All exterior entrances to the
crawl space appear to be sealed.
H.2 Initial Radon Tests
In April 1988, 35 charcoal canister radon tests
showed that 34 were above 4 pCi/L, 15 were
above 8 pCi/L, and 1 was above 20 pCi/L (23.5
pCi/L). The radon levels were generally higher
in the rooms over the crawl space. All of the
screening and confirmation tests were made
when the building was unoccupied and the
HVAC system was turned off.
H.3 Building Plan Inspection
The original school, which is approximately
150,000 square feet in area, was built in 1936
over a crawl space. In 1967 a slab-on-grade
addition was built onto two sides of the old
building. The crawl space has a dirt floor and
the wooden floor joists rest on a maze of
masonry walls. The foundation plans and
specifications for the slab call for 4 inches of
aggregate under the slabs. The addition was
constructed so that its floor would be at the
same level as the crawl space floor. Retaining
walls were built and shale fill was used to raise
the leveL
H.4 Walk-Through Building Inspection
The crawl space is accessible through hatches in
the floor, but the crawl space size and maze of
support walls do not appear to offer good
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access for laying down a ground cover for
submembrane depressurization (SMD), as is
often done in houses built over crawl spaces.
Some plumbing pipes are in the crawl space and
all exterior vents appear to have been sealed for
security and to prevent the pipes from freezing.
H.S Pre-Mitigation Diagnostics
Since there is little experience with radon
mitigation of large crawl spaces, there are no
guidelines for diagnostic analysis. Blower door
testing of the crawl space was considered, but
the installation of a 500 cfm exhaust fan was
simpler to evaluate. Radon grab samples taken
before the fan installation showed about 30
pCi/L in the crawl space.
H.6 First-Stage Mitigation
A Kanalflakt GV9 fan was mounted on one of
the wooden panels that covered the crawl space
vents. This fan can move 510 cfm at 0.0
pressure. It was mounted so that it would
exhaust air from the crawl space. No crawl
space sealing was done before evaluation of the
system's performance.
The fans were turned off over the Christmas
holiday weekend, and continuous radon
monitors were placed in the crawl space and the
main office to determine if the crawl space
exhaust fan was reducing the radon. The
monitoring showed that the crawl space levels
dropped slightly when the fan was running. In
addition, the office radon seemed to be well
below 4 pCi/L when school was in session and
the HVAC fans were operating. Pressure
differentials in the crawl space did not change
measurably (less than 0.001 inch WC) due to
crawl space exhaust Can operation. Calculations
of these results estimate that there is at least 10
square feet of leakage in the crawl space
envelope.
H.7 Second-Stage Mitigation
The school will be retested with the HVAC
system operating to determine the mitigation
effect. If the HVAC system induces a positive
pressure in all parts of the building, then the
radon problems may be mitigated while the
HVAC fans are operating. Further investigation
will be required to determine if the HVAC
mitigation can be relied on under all operating
conditions, and whether there is a remaining
radon exposure problem to those who use the
school outside of normal operating hours when
the HVAC fans are off. The crawl space
exhaust fan seems to be lowering the radon
levels slightly, but it does not seem to be
creating much of a pressure barrier to prevent
soil gas from moving into the building. To
increase the depressurization, several large holes
between the crawl space and the boiler room
will be sealed.
A SSD system will be installed in the
slab-on-grade part of the school. This system
will be mounted externally by drilling a 6-inch
diameter hole in the retaining wall, just below
the slab level A Kanalflakt T3B in-line fan will
be mounted on a 6-inch stack that exhausts
above roof level.
H.8 Conclusion
Several more mitigation stages are anticipated in
order to obtain an effective radon mitigation
system for this complex school. The final
mitigation system will probably combine a
number of methods due to the school's complex
substructure.
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APPENDIX C: STATE RADON OFFICES AND EPA REGIONAL
RADIATION PROGRAM OFFICES
C.1 STATE RADON OFFICES
Radiological Health Branch
Alabama Department of Public Health
State Office Building
Montgomery, AL 36130
(205) 261-5313
Alaska Dept. of Health and Social Services
P.O. Box H-06F
Juneau, AK 99811-0613
(907) 586-6106
Arizona Radiation Regulatory Agency
4814 South 40th Street
Phoenix, AZ 85040
(602) 255-4845
Div. of Radiation Control and Emergency
Management
Arkansas Department of Health
4815 Markham Street
Little Rock, AR 72205-3867
(501) 661-2301
Indoor Quality Program
California Department of Health Services
2151 Berkeley Way
Berkeley, CA 94704
(415) 540-2134
Radiation Control Division
Colorado Department of Health
4210 East llth Avenue
Denver, CO 80220
(303) 331-4812
Connecticut Department of Health Services
Toxic Hazards Section
150 Washington Street
Hartford, CT 06106
(203) 566-3122
Division of Public Health
Delaware Bureau of Environmental Health
P.O. Box 637
Dover, DE 19903
(302) 736-4731
DC Dept of Consumer and Regulatory Affairs
614 H Street, NW, Room 1014
Washington, DC 20001
(202) 727-7728
HRS Office of Radiation Control/Radon
1317 Wirewood Boulevard
Tallahassee, FL 32399-0701
(904) 488-1525
(800) 543-8279 (Consumer inquiries only)
Georgia Dept of Natural Resources
Environmental Protection Division
205 Butler Street, NE
Floyd Towers East, Suite 1166
Atlanta, GA 30334
(404) 656-6905
Environmental Protection and Health Services
Division
Hawaii Department of Health
591 Ala Moana Boulevard
Honolulu, HI 96813
(808) 548-4383
Bureau of Preventive Medicine
450 West State Street
Fourth Floor
Boise, ID 83720
(208) 334-5927
Illinois Department of Nuclear Safety
Illinois State Board of Health
1301 Knotts Street
Springfield, IL 62703
(217) 786-6399
(800) 225-1245
Division of Industrial Hygiene and Radiological
Health
Indiana State Board of Health
1330 W. Michigan Street
P.O. Box 1964
Indianapolis, IN 46206-1964
(800) 272-9723
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Bureau of Environmental Health
Iowa Department of Public Health
Lucas State Office Building
Des Moines, IA 50319-0075
(800383-5992
Bureau of Air Quality and Radiation Control
Attention: Radon
Forbes Field, Building 740
Topeka, KS 66620-0110
(913) 296-1560
Radiation Control Branch
Cabinet for Human Resources
275 East Main Street
Frankfort, ICY 40621
(502) 564-3700
Louisiana Nuclear Energy Division
P.O. Box 14690
Baton Rouge, LA 70898-4690
(504) 925-4518
Division of Health Engineering
Maine Department of Human Services
State House Station 10
Augusta, ME 04333
(207) 289-3826
Division of Radiation Control
Maryland Dept of Health and Mental Hygiene
201 W. Preston Street
Baltimore, MD 21201
(301) 631-3300
(800) 872-3666
Radiation Control Program
Massachusetts Department of Public Health
23 Service Center
Northhampton, MA 01060
(413) 586-7525
(617) 727-6214 (Boston)
Michigan Departtkfcat of Public Health
Division of Radjofcfkal Health
3500 North Logan
P.O. Box 30035
Lansing, MI 48909
(517) 335-8190
Section of Radiation Control
Minnesota Department of Health
P.O. Box 9441
717 SE Delaware Street
Minneapolis, MN 55440
(612) 623-5348
(800) 652-9747
Division of Radiological Health
Mississippi Department of Health
P.O. Box 1700
Jackson, MS 39125-1700
(601) 354-6657
Bureau of Radiological Health
Missouri Department of Health
1730 E. Elm, P.O. Box 570
Jefferson City, MO 65102
(800) 669-7236 (Missouri only)
Occupational Health Bureau
Montana Dept of Health and Environmental
Sciences
Cogswell Building A113
Helena, MT 59620
(406) 444-3671
Division of Radiological Health
Nebraska Department of Health
301 Centennial Mall South
P.O. Box 95007
Lincoln, NE 68509-5007
(402) 471-2168
Radiological Health Section
Health Division
Nevada Department of Human Resources
505 East King Street, Room 203
Carson City, NV 89710
(702) 885-5394
New Hampshire Radiological Health Program
Health and Welfare Building
6 Hazen Drive
Concord, NH 03001-6527
(603) 271-4588
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New Jersey Dept of Environmental Protection
380 Scotch Road, CN-411
Trenton, NJ 08625
(609) 530-4000/4001 or (800) 648-0394 (in state)
or (201) 879-2062 (Northern NJ Radon Field
Office)
New Mexico Environmental Improvement Div.
Community Services Bureau
1190 St. Francis Drive
Harold Runnels Building
Santa Fe, NM 87503
(505) 827-2948
Bureau of Environmental Radiation Protection
New York State Health Department
2 University Place
Albany, NY 12203
(800) 342-3722 (NY Energy Research &
Development Authority)
Radiation Protection Section
North Carolina Department of Human
Resources
701 Harbour Drive
Raleigh, NC 27603-2008
(919) 733-4283
Division of Environmental Engineering
North Dakota Department of Health and
Consolidated Laboratory
Missouri Office Building
1200 Missouri Avenue, Room 304
P.O. Box 5520
Bismarck, ND 58502-5520
(701) 224-2348
Radiological Health Program
Ohio Department of Health
1224 Kinnear Road, Suite 120
Columbus, OH 43212
(614) 644-2727 or
(800) 523-4439 (ta *t*te only)
Radiation and Spedal Hazards Service
Oklahoma State Department of Health
P.O. Box 53551
Oklahoma City, OK 73142
(405) 271-5221
Oregon State Health Department
1400 S.W. 5th Avenue
Portland, OR 97201
(503) 229-5797
*
Bureau of Radiation Protection
Pennsylvania Department of Environmental
Resources
P.O. Box 2063
Harrisburg, PA 17120
(717) 787-2480 or
(800) 237-2366 (in state only)
Puerto Rico Radiological Health Division
G.P.O. Call Box 70184
Rio Piedras, PR 00936
(809) 767-3563
Division of Occupational Health and Radiation
Control
Rhode Island Department of Health
206 Cannon Building
75 Davis Street
Providence, RI 02908
(401) 277-2438
Bureau of Radiological Health
South Carolina Department of Health and
Environmental Control
2600 Bull Street
Columbia, SC 29201
(803) 734-4700/4631
Office of Air Quality and Solid Waste
South Dakota Department of Water and
Natural Resources
Joe Foss Building, Room 416
523 E. Capital
Pierre, SD 57501-3181
(605) 773-3153
Division of Air Pollution Control
Custom House
701 Broadway
Nashville, TN 37219-5403
(615) 741-4634 ..
Bureau of Radiation Control
Texas Department of Health
1100 West 49th Street
Austin, TX 78756-3189
(512) 835-7000
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Division of Environmental Health
Bureau of Radiation Control
288 North 1460 West
P.O. Box 16690
Salt Lake City, UT 84116-0690
(801) 538-6734
Division of Occupational and Radiological
Health
Vermont Department of Health
Administration Building
10 Baldwin Street
Montpelier, VT 05602
(802)828-2886
Bureau of Radiological Health
Department of Health
109 Governor Street
Richmond, VA 23219
(804) 786-5932 or
(800) 468-0318 (in state)
Environmental Protection Section
Washington Office of Radiation Protection
Thurston Airdustrial Center
Building 5, LE-13
Olympia, WA 98504
(206) 753-5962
Radon Hotline (800) 323-9727
Industrial Hygiene Division
West Virginia Department of Health
151 llth Avenue
South Charleston, WV 25303
(304) 348-3526/3427
(800) 922-1255
Division of Health
Section of Radiation Protection
Wisconsin Department of Health and Social
Services
5708 Odana Road
Madison, WI 53719
(608) 273-6421
Radiological Health Services
Wyoming Department of Health and Social
Services
Hathway Building, 4th Floor
Cheyenne, WY 82002-0710
(307) 777-7956
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C.2 EPA REGIONAL OFFICES
Region Address/Telephone
1 U.S. Environmental Protection Agency
APT-2311
John F. Kennedy Federal Building
Boston, MA 02003
(617) 565-3234
States in Region
Connecticut, Maine, Massachusetts,
New Hampshire, Rhode Island,
Vermont
U.S. Environmental Protection Agency
2AWM:RAD
26 Federal Plaza
New York, NY 10278
(212) 264-4418
New Jersey, New York, Puerto Rico,
Virgin Islands
U.S. Environmental Protection Agency
3AM12
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-8320
Delaware, District of Columbia,
Maryland, Pennsylvania, Virginia,
West Virginia
U.S. Environmental Protection Agency
345 Courtland Street, N.E.
Atlanta, GA 30365
(404)347-3907
Alabama, Florida, Georgia, Kentucky,
Mississippi, North Carolina, South
Carolina, Tennessee
U.S. Environmental Protection Agency
5AR-26
230 South Dearborn Street
Chicago, IL 60604
(800) 572-2515 (Illinois)
(800) 621-8431 (other states in region)
Illinois, Indiana, Michigan,
Minnesota, Ohio, Wisconsin
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U.S. Environmental Protection Agency
6T-AS
1445 Ross Avenue
Dallas, TX 75202-2733
(214) 655-7208
Arkansas, Louisiana, New Mexico,
Oklahoma, Texas
U.S. Environmental Protection Agency
726 Minnesota Avenue
Kansas City, KS 66101 ,
(913) 236-2893
Iowa, Kansas, Missouri, Nebraska
U.S. Environmental Protection Agency
8HWM-RP
999 18th Street, Suite 500
Denver, CO 80202-2405
(303) 293-1709
U.S. Environmental Protection Agency
A-l-1
215 Fremont Street
San Francisco, CA 94105
(415) 974-8378
Colorado, Montana, North Dakota,
South Dakota, Utah, Wyoming
American Samoa, Arizona, California,
Guam, Hawaii, Nevada
10
U. S. Environmental Protection Agency
AT-082
1200 Sixth Avenue
Seattle, WA 98101
(206) 442-7660
Alaska, Idaho, Oregon, Washington
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