United States
Environmental Protection
Agency
Air and
Radiation
(6604J)
EPA402-R-94-008
April 1994
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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 material. Nor does EPA
assume any liability for, or for damages arising from, the use of any information, method, or process
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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ACKNOWLEDGEMENTS
The information contained in this document is based largely on the evaluations and
demonstrations conducted by the School Evaluation Program (SEP) of the Environmental Protection
Agency's (EPA) Office of Radiation and Indoor Air and the research conducted by the Air and
Energy Engineering Research Laboratory of EPA's Office of Research and Development.
Susan Galbraith of Cogito Technical Services was the primary author of this document
which was prepared under contract number 68D20185 with Sandford Cohen & Associates. Terry
Brennan of Camroden Associates prepared many of the figures in this document.
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 have helped
significantly to improve the completeness, accuracy, and clarity of the document. The following
reviewers offered input: Stephany DeScisciolo, David Rowson, Lee Salmon, Anita Schmidt, and
Chris Bayham of EPA's Radon Division; A.B. Craig, Kelly Leovic, and Tim Dyess of EPA's Office
of Research and Development; John Girman of EPA's Indoor Air Division; Sam Windham of EPA's
National Air and Radiation Environmental Laboratory; Katie Mazer of EPA Region 1; Paul A.
Giardina and Larainne Koehler of EPA Region 2; Lewis Fellison of EPA Region 3; Chuck Wakamo
and Patsy Brooks of EPA Region 4; Donna M. Ascenzi and Mike Miller of EPA Region 6; Michael
Bandrowski of EPA Region 9; Ronald Pass of Alabama; Donald Plater and Joyce Spencer of Iowa;
William Bell of Massachusetts; George Bruchmann of Michigan; Joseph Milone of Nebraska;
Tonalee Key of New Jersey; Craig Kneeland of New York; Rich Prill of Washington; Bill Angell
of Midwest Universities Radon Consortium; Bill Brodhead of WPB Enterprises Inc.; William Turner
of H.L. Turner Group; Andrew Persily of National Institute of Standards and Technology; Gary
Hodgden of Midwest Radon; Brad Turk of Mountain West Technical Associates; Stephen Albright
and Jack Hughes of Albright Hughes Construction Inc.
A special thanks is extended to all the school districts who volunteered their schools for
evaluation and demonstration work. The local state and regional EPA support which contributed
to the logistics of the SEP was invaluable to the program's success. Your support was much
appreciated.
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Contents
Contents
Purpose 1-1
1.0 Introduction 1-2
1.1 Radon Facts 1-5
Figure 1-1: Deaths from Radon and Other Causes 1-6
1.2 Radon Measurements 1-7
2.0 The Indoor Environment and Radon 2-1
2.1 Building Dynamics 2-2
Figure 2-1: Air Pressure Relationships 2-4
Table 2-1: Selected Ventilation Recommendations 2-8
2.2 Radon Mitigation Strategies 2-9
Figure 2-2: Active Soil Depressurization 2-11
3.0 Evaluating and Correcting Radon Problems 3-1
3.1 Problem Assessment and Strategy 3-1
Figure 1-2: School Mitigation Flowchart 3-3
3.2 The Initial Investigation Team 3-8
3.3 Evaluate and Map Your Radon Test Results 3-10
Sample Working Floorplan 1 3-13
3.4 Initial Investigation 3-14
Figure 3-2: Typical Mechanical Plan and Equipment Schedule 3-18
Figure 3-3: Design Air Pressures 3-20
Figure 3-4: Design Outdoor Air Flow Rates 3-22
Sample Working Floorplan 2 3-23
Sample Working Floorplan 3 3-26
Sample Working Floorplan 4 3-34
4.0 HVAC System Restoration 4-1
4.1 Restore the Ventilation System 4-1
Sample Working Floorplan 5 4-4
4.2 Seal Large Radon Entry Points 4-5
Figure 4-1: Sealing a Sump Hole 4-6
IV
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Contents
5.0 Retest Radon Levels 5-1
5.1 Evaluate Retest Results 5-2
Figure 5-1: Radon Levels and Control Cycles 5-3
Sample Working Floorplan 6 5-4
6.0 Detailed Investigation 6-1
6.1 Assemble a Radon Team 6-1
6.2 Radon Mitigation Techniques 6-2
Figure 6-1: ASD Beneath a Membrane 6-5
Figure 6-2: ASD with Multiple Suction Points 6-5
6.3 Elements of the Detailed Investigation 6-7
Figure 6-3: Elements of the Detailed Building Investigation 6-8
Sample Working Floorplan 7 6-10
Figure 6-4: Flowchart for Evaluating ASD-based Mitigation 6-12
Sample Working Floorplan 8 6-17
Figure 6-5: Vacuum Test of Pressure Field Extension 6-25
Figure 6-6: Fan Door Test Results 6-28
Figure 6-7: Carbon Dioxide as an Indicator of Ventilation 6-33
Figure 6-8: Calculating the Percent of Outdoor Air 6-35
Figure 6-9: Converting % Outdoor Air to CFM/Person 6-35
Sample Working Floorplan 9 6-36
7.0 Design and Implementation of Mitigation Techniques 7-1
7.1 Active Soil Depressurization 7-3
7.2 Pressurization 7-8
Figure 7-1: Mitigation by Pressurization 7-10
7.3 Dilution 7-11
Figure 7-2: Mitigation by Dilution . 7-13
Sample Working Floorplan 10 7-14
8.0 Post-Mitigation Measurements 8-1
Figure 8-1: Post-Mitigation Measurements 8-1
8.1 Evaluate Results of Post-Mitigation Radon Measurements 8-2
9.0 Long-Term Radon Management 9-1
9.1 Periodic Radon Testing 9-1
9.2 HVAC System Maintenance 9-2
9.3 Installation of New HVAC Equipment, Building Renovations 9-5
10.0 Special Considerations 10-1
10.1 Building Codes 10-1
10.2 Worker Protection 10-2
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Contents
Appendix A: Glossary and Acronyms
Glossary
Acronyms
Appendix B Resources
References
Regional Radon Training Centers
EPA Regional Offices
State Radon Contacts
Bibliography
Appendix C Metric Conversion Factors
Appendix D Mitigation Cost Information
Appendix E Case Studies
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B-3
B-4
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VI
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Overview
Overview
This document will assist you in determining the best way to reduce elevated
radon levels found in a school. It is designed to guide you through the process of
confirming a radon problem, selecting the best mitigation strategy, and directing the
efforts of a multidisciplinary team assembled to address elevated radon levels in a
way that will contribute to the improvement of the overall indoor air quality of the
school.
Chapters 1 and 2 review what radon is, why it is a concern, and the mechanisms
by which it enters and accumulates in a building. Chapters 3 and 4 outline the
Initial Investigation, in which you will examine the condition of your school's
ventilation system and determine whether restoring the ventilation system to its
intended operating condition could reduce radon levels to below EPA's action level
of 4 pCi/L. This determination is based on: 1) the school's pre-mitigation radon
levels, and 2) a physical inspection of the ventilation system. If significant
improvements are made to the ventilation system, Chapter 5 discusses the option of
retesting to determine whether this action alone has solved the problem.
Chapter 6 discusses the Detailed Investigation that may be necessary if: 1) pre-
mitigation levels are above 10 pCi/L, or 2) improving the ventilation system did not
sufficiently reduce radon levels. Chapter 7 describes active subslab depressurization
systems, which have proven effective at reducing extremely elevated radon levels
in both residences and schools. Chapters 8 and 9 outline the process of making post-
mitigation measurements and discuss steps to ensure the long-term effectiveness of
your mitigation strategy. Chapter 10 provides information regarding building codes
and worker protection. This document also offers two case studies based on real-life
experiences of EPA's research team and cost information for six research sites.
Each chapter of the guide builds upon the previous chapter and makes use of
photographs, floor plans, and graphs to illustrate the steps involved in designing
the proper mitigation strategy for a school. The guide is not meant to be a "how-to"
manual on radon mitigation, but rather a resource for managing a team made up of
radon mitigation contractors, HVAC engineers, school personnel, and parent
representatives. EPA believes such a team is helpful to achieve successful
mitigation.
By following this guide, you will not only have reduced your school's radon
levels, but you will also have a good understanding of the steps necessary to ensure
the integrity of your mitigation strategy.
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Purpose/Introduction
Purpose
This document presents the process of
radon diagnostics and mitigation in schools. It
describes what radon is, why it is a concern,
and strategies for correcting radon problems.
It also discusses how to select the best
mitigation approach, based on indoor radon
concentrations and features of the building
and its mechanical systems.
Radon diagnostics means\evatuating
Jbtiildirig characteristics "and* radon
41sfcibta.tion to understand the causes
of a radon problem,,1 " <. *> '
Mitigation means treatment or
1 correction of a problem, .' .'
EPA has found that effective radon mitigation in schools requires specialized
knowledge in several disciplines. For this reason, school radon problems can best be
resolved through the use of a team approach. This document is targeted at the team
leader, the person responsible for coordinating the effort and achieving satisfactory
compliance with the technical objectives.
The team leader may be the school's facility manager or a hired consultant such
as a mechanical engineer or radon mitigation contractor. The team leader should be
familiar with radon mitigation diagnostics and mitigation strategies in order to
identify qualified team players (e.g., district personnel, consultants, contractors) and
coordinate their efforts. This document provides background information about
diagnostic and mitigation techniques that have been successfully applied in school
buildings. It does not address radon measurement protocols. Radon measurement
protocols for schools can be found in the EPA document entitled Radon
Measurement in Schools - Revised Edition (see Appendix B).
EPA has extensively researched two highly successful radon control strategies:
mitigation using active soil depressurization (ASD), and 2) mitigation using the
school's ventilation system. This document presents information about both
strategies and assists you in choosing the approach that best fits your school.
1)
School staff are an important factor in the success of any radon control program.
Facility staff bring valuable experience to building investigations and will probably
be responsible for monitoring the operation of radon mitigation systems. The
school administration must support the activities necessary to long-term success,
but facility staff generally carry out those activities. This document can help a school
district use the skills and resources available within its own staff when possible and
be a well-informed consumer of outside services when necessary.
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Purpose/Introduction
1.0 Introduction
Radon is a naturally-occurring radioactive gas found in the soil. It can enter
buildings through cracks and openings to the ground and accumulate indoors until
it reaches dangerous concentrations. Radon has been identified as the second
leading cause of lung cancer after smoking. The higher the radon concentration and
the longer the exposure time, the higher the risk of developing radon-related lung
cancer.
Radon is odorless, tasteless, and colorless. It does not announce its presence by
smelling like spoiled food or making our eyes itch. In fact, we need specialized
instruments to detect radon at all. Testing for radon is straightforward and radon
problems can be corrected, but the motivation to act must come from our ability to
think about the health risks.
The U.S. Environmental Protection
Agency (EPA) recommends that all schools
test for radon and mitigate areas with elevated
concentrations. EPA's National School Radon
picocuries per liter: Radon concentrations
are described on the basis of the
Survey, performed during 1990, obtained radioactivity per unit volume of ait,
radon measurements from 927 randomly-
selected schools across the United States.
Almost one out of every five schools surveyed had at least one ground-contact
room with radon above EPA's action level of 4 picocuries per liter (4 pCi/L) using
short term measurement devices. Based on these initial measurements, it appears
that approximately 15,000 U.S. schools have at least one room with a potential radon
problem. Radon is often unevenly distributed within a building. Overall, short-
term radon concentrations in roughly 2.7% of all ground-contact schoolrooms were
over 4 pCi/L, indicating a nationwide total of 73,000 schoolrooms with a potential
radon problem.
EPA has developed various resources to promote accurate and meaningful radon
measurements and assist in correcting radon problems. EPA's Office of Radiation
and Indoor Air (ORIA) and Office of Research and Development (ORD) have been
studying a wide variety of schools across the country that have elevated levels of
radon. ORIA's School Evaluation Program (SEP) and ORD's school research and
development program were intended to identify diagnostic techniques that can be
useful for understanding the dynamics of radon entry and movement in schools
and to test mitigation strategies that can control the radon problem. An ORD
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Purpose/Introduction
document, Radon Prevention in the Design and Construction of Schools and Other
Large Buildings, suggests ways to keep radon out of new buildings (see Appendix B
for more information).
In addition to radon, indoor air in schools can contain a variety of other
contaminants whose effects range from discomfort to serious, even life-threatening
health hazards. Both elevated radon concentrations and other indoor air quality
(IAQ) problems are often caused or made worse by deficiencies in the ventilation
system. EPA research indicates that many of our nation's schools are not properly
ventilated with outdoor air. Their heating, ventilation, and air conditioning
(HVAC) systems frequently do not introduce
enough outdoor air to meet current standards
nor to meet the standards that applied when
the buildings were constructed. Inadequate
outdoor air ventilation can lead to
accumulation of radon and other indoor air
contaminants. Unfortunately, most people
do not understand the potential health effects
of poorly maintained ventilation equipment.
The term ventilatian-as used ifi this J
document refers to the flow of ak
info', within, and'out of 'a building. '
'Mechanical air .handling equipment'
of ten, blends outdoor ventilation ak .
with recirculated room ak. ' <
EPA believes that correction of ventilation problems should be an important part
of school radon control programs because ventilation is a critical element of indoor
air quality. In addition, EPA research findings indicate that schools should identify
and correct ventilation system malfunctions and deficiencies as an initial step in
responding to a radon problem, because:
1) The indoor concentration of an airborne contaminant such as radon is a result of
the dynamic balance between the rate of contaminant entry (or production) and the
rate of contaminant removal, both of which are strongly affected by the ventilation
system. It is best to have the ventilation system operating as desired before
conducting a detailed investigation, so that the data collected represents "normal"
conditions.
2) Changing ventilation system operation can have the effect of increasing or
decreasing radon levels. In most schools, correcting outdoor air ventilation
inadequacies will result in lower radon levels. In others, correcting some
ventilation malfunctions (e.g., replacing a broken exhaust fan) could increase indoor
radon concentrations.
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Purpose/Introduction
3) If the ventilation system creates strong negative pressures in the building,
ventilation adjustments may be needed before any other approach to radon control
can be successful.
Design goals, differences in age, construction materials, mechanical equipment,
number of occupants, room layout, construction, and operation make each building
unique. This document discusses how to select the radon mitigation strategy best
suited to the unique features of your building and its mechanical systems. You will
learn how to conduct a walkthrough inspection to identify radon entry points and
assess the condition of the ventilation system. This document also describes the
diagnostic techniques used by researchers and professional building investigators.
Many schools may be able to reduce radon below 4 pCi/L by identifying and
correcting ventilation system problems. This approach generally improves indoor
air quality, extends the useful life of buildings, furnishings, and mechanical
equipment, and typically improves the health, and comfort of students and staff. A
ventilation-based approach to radon control may also help build support for facility
operation as a budget priority. However, this mitigation strategy will not work in
every school and requires conscientious long-term maintenance. Radon
concentrations may be too high to treat successfully by using the ventilation system
alone. Some building structures are not suited to this approach, and some buildings
are not equipped with mechanical ventilation.
ASD prevents radon eritry by , ,
reducing air pressure in the soil
beneath the foundation.
EPA has also developed and tested another radon
control technique known as ASD (active soil
depressurization) that has been used successfully in
both residential and non-residential buildings.
Effective ASD systems can be designed for most
building designs and site conditions. ASD has little or
no effect on other building functions and causes only small increases in energy
consumption. However, ASD only treats soil gas contaminants such as radon; it
will not address other indoor air quality problems.
The source of radon beneath your school will always be there. Any radon control
strategy must be maintained for the lifetime of the building. This document will
help the school district to decide what radon control strategy is best suited to its
needs and establish a program that prevents recurrence of the radon problem.
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Purpose/Introduction
1.1 Radon Facts
Radon gas is continually released by uranium-bearing rocks and soil as the
uranium undergoes natural radioactive decay. The gas moves through the soil
freely because it is chemically nonreactive and does not combine with other
materials. When the radon gas reaches the outdoor air, it is quickly diluted to low
concentrations. However, radon can accumulate under the slabs and foundations of
buildings and can easily enter through cracks and openings, sometimes causing high
indoor concentrations.
Radon decays into other radioactive elements (which are solid particles) often
referred to as radon decay products or radon progeny. When radon progeny are
inhaled, they can lodge in the lungs and deliver radiation doses to sensitive lung
tissue as the progeny continue to decay.
The health risks of radon gas have been clearly recognized by organizations such
as the National Academy of Sciences, the U.S. Public Health Service, the Centers for
Disease Control and Prevention, the World Health Organization, the American
Lung Association, the American Medical Association, EPA and many other national
and international health and science organizations. Radon is a known human
carcinogen and is estimated to be the second leading cause of lung cancer. Only
smoking causes more lung cancer deaths. EPA estimates that radon causes between
7,000 - 30,000 lung cancer deaths each year in the U.S. By comparison, roughly 23,000
people in this country die as a result of drunk driving accidents, 4,400 die of injuries
caused by fires, and 1,000 are killed in airplane crashes annually (as illustrated in
Figure 1-1). Scientists agree that the risks associated with radon increase as the
concentration and length of exposure increase. In addition, smoking combined with
radon is an especially serious health risk. The risk of dying from radon related lung
cancer is much greater for smokers than it is for non-smokers.
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Purpose/Introduction
rage Annual Deaths (U.S.A.)
M M IO N>
i i i i
""
11 11 ii
Drunk Radon Drowning Fire Air
driving transport
Fig. 1-1: Deaths from Radon and Other Causes
The numbers of deaths from causes other than radon
come from a 1990 report of the National Safety Council.
EPA currently recommends taking action to reduce radon levels in schools and
homes where the concentration of radon is 4.0 pCi/L or higher based on follow-up
measurement results. Based on this action level, this document defines mitigation
as successful when radon concentrations during occupied periods are below 4 pCi/L.
However, any radon exposure poses a risk, even at concentrations below 4.0 pCi/L,
because radon is a carcinogen with no known threshold level (i.e., the concentration
below which no potential harm exists).
Soil gas (which consists of air, water vapor, and any natural or synthetic
contaminants that are found in the spaces between soil particles and the cracks in
bedrock) is the most common source of radon problems in the United States. Soil
gas is drawn into buildings by pressure differentials between the soil surrounding
the substructure and the building interior. Radon can also be found in natural
aquifers, from which it may enter private wells.
The amount of radon in a given room will depend on five factors:
source strength the concentration of radon in the soil or bedrock underlying
the building
the permeability of material below the slab the ability of soil gas to move
through pores and cracks in the fill, soil, and rock beneath the slab
the number and size of radon entry routes openings to the ground
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Purpose/Introduction
the size and direction of pressure differentials between indoors and the
subslab
the outdoor air ventilation rate the amount of outdoor air brought into the
room
Radon control strategies involve influencing the last three factors. Large radon
entry routes can be sealed.
Pressure differentials and
outdoor air ventilation rates
can be changed by adjusting
the existing building
ventilation system or
installing new ventilation
equipment. Active soil
The term pressure? differential is tised to describe the ฐ
difference betWeert air pressures measured at two'Iocations;
J 05 * a 1 > J c*ฐo
' " ซ J- c * >*
A negative'pressure'field is,an area fltiatฐis maintained at '
a relatively lower air pressurei;fen an adjoinMg location.
depressurization (ASD) works
by creating and maintaining a negative pressure field in the soil below the
foundation.
1.2 Radon Measurements
- BPA's KMPprogrartt evaluates the accuracy of.
radon measurement devices and^fie people ,^ho use'
thenv EPA issues individual identification'ca^rds- -
to testers, who pass JheKMP measurement ' *
'"proficiency test Yotfirstate radon otfice has lists of x
s^MP, program participanls. Some states also - '
operate, ftiejir own certification programs'^
EPA's radon measurement protocol
for schools is described in Radon
Measurement in Schools; Revised
Edition (see Appendix B), which
replaces the earlier Radon
Measurement in Schools: An Interim
Report. Use only measurement
devices and testing contractors that are
listed with EPA's Radon Measurement
Proficiency (RMP) program or are
state-certified. Many states require the use of certified personnel to conduct radon
testing or install radon reduction systems. Ask your state radon contact for a list of
qualified contractors. Schools can use their own staff members to test for radon or
use professional radon measurement contractors (unless prohibited by state laws
and/or regulations). If school staff are used to perform the tests, EPA recommends
that they receive training in radon measurement (see Radon Measurement in
Schools; Revised Edition for recommended training).
Radon Measurement in Schools; Revised Edition calls for an initial phase during
which short-term measurements should be made in all frequently-occupied rooms
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Purpose/Introduction
that contact the ground, including classrooms, gymnasiums, cafeterias, and offices.
EPA recommends testing during the coldest months, when the heating system is
operating and windows and doors are closed (except for normal exit and entry).
HVAC equipment should be operated normally, including normal occupied-
unoccupied cycling, and testing should be scheduled to take place during the week.
Short-term tests are from two to ninety days in duration, providing a
determination of whether or not high radon concentrations are present and
whether additional measurements are needed. EPA does not recommend testing in
locker rooms and kitchens, because high humidity affects some radon measurement
devices. Other rooms not recommended for inclusion in testing programs include
hallways, toilets, closets, and storerooms.
EPA's Indoor Radon and Radon Decay Product Measurement Protocols describes
a variety of instruments for measuring indoor radon concentrations. A minimum
of a 48 continuous hour test period should be used. Devices that produce results
within a short time (e.g., two- to five- day measurements) offer the advantage of
rapid feedback, allowing a prompt response if radon levels are high.
The school test protocol is designed to identify all regularly-occupied ground
contact rooms that may have elevated radon concentrations. Because radon levels
can vary dramatically over time, EPA strongly advises that schools not expend funds
to reduce radon concentrations on the basis of initial short-term tests alone.
A second, follow-up test should be conducted in ALL areas where initial test
results show radon levels at or over 4 pCi/L. This test may be done with either a
short-term or a long-term
measurement device. Devices
that measure radon over a period
The annual average exposure to radon is the exposure
as a function of time. Because of seasonal variations in
radon concentrations, occupant risk can best be -
evaluated by determining the annual average
exposure. , , , -' "
of months are more
representative of annual average
exposures. Indoor radon
concentrations have been
observed to vary seasonally, at
least partly because outdoor air
ventilation rates are usually reduced when outdoor temperatures are extreme. The
purpose of the follow-up test is to make sure that you actually have a radon problem
ki areas where the initial result was greater than or equal to 4 pCi/L. Follow-up
measurements may also be considered for rooms: 1) in which initial test results are
only slightly below 4 pCi/L and 2) adjacent to areas with radon concentrations equal
to or above 4 pCi/L. HVAC equipment should operate normally, as before.
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Purpose/Introduction
If the follow-up test was short-term (less than 90 days), calculate the average of
the initial and follow-up test results for each test location. Corrective action is
needed if the average radon level in any area is 4.0 pCi/L or higher. If the follow-up
test period was long-term (i.e., over 90 days), disregard the initial test results and use
only the long-term test, taking corrective action in areas with long-term test results
of 4.0 pCi/L or higher.
Indoor radon levels can change over time. Openings to earth may appear or
enlarge as buildings settle or new wings are added to existing buildings. Air
circulation patterns and pressure relationships change when fans are added,
removed or replaced by equipment of a different size. As a result, rooms in which
radon test results are below 4 pCi/L may develop higher radon concentrations in the
future. EPA recommends that schools be periodically retested.
For complete information on EPA's recommended testing approach for schools,
see Radon Measurement in Schools - Revised. Edition, EPA 402-R-92-014.
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The Indoor Environment and Radon
2.0 The Indoor Environment and Radon
This section discusses radon in the context of the overall indoor environment.
Radon is an indoor air quality problem and is often found in conjunction with
other IAQ problems. Building air dynamics that impact radon entry and
distribution will also be discussed. The radon mitigation strategies that are typically
used in school buildings are then presented and discussed. These strategies control
radon by influencing the air dynamics in the building.
This document is primarily concerned with radon and the aspects of ventilation
that affect indoor radon concentrations. It does not provide detailed information
about other indoor air contaminants or other aspects of the indoor environment. If
you are interested in the potential for indoor air quality (IAQ) problems, a brief
discussion on other common indoor air contaminants is presented below.
Information about IAQ is available from other sources to supplement the discussion
that follows. For example, EPA and the National Institute for Occupational Safety
and Health (NIOSH) have produced Building Air Quality, an IAQ guidance
document for building owners and managers of non-residential buildings that can
be obtained by calling the EPA's IAQ Information Clearinghouse at 800-438-4318.
EPA is also developing IAQ guidance for schools.
Radon is an important indoor air contaminant because it can cause lung cancer.
However, radon is only one part of the IAQ picture in your school. Indoor air
typically contains a variety of contaminants at low concentrations. It is important to
be aware of potential IAQ problems as you perform the radon control investigations
outlined in this document. Awareness of potential IAQ problems is key to
maintaining an indoor environment that is safe for the occupants. Identifying and
correcting IAQ problems may help prevent future complaints and illnesses.
As you inspect each outdoor air intake to evaluate damper operation, think
about the intake location. Are there sources of odors or pollutants nearby? ("Near"
is a relative term - consider the wind direction and the strength of the contaminant
source.) For example, if vehicles idle near an outdoor air intake, exhaust fumes may
be drawn into the building. Rooftop air intakes can create problems if they are
located close to exhaust outlets or sewer vents, or if water puddles on the roof
remain long enough to become sites for microbiological growth.
A puddle is an obvious location for microbiological growth, but IAQ problems
can develop in much smaller amounts of water. Persistent high humidities can
stimulate mold and mildew growth on walls, windows, and other surfaces.
Condensate drain pans that don't drain completely often show signs of
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The Indoor Environment and Radon
microbiological growth, such as visible algae or odors.
Many chemicals from the cleaning agents used by custodial staff to the
chemicals used in science classes can
cause IAQ problems. Proper storage,
The term plenum is used to describe a) portions of
the air distribution system that make use of the
building structure, and b) -the sheet metal that
connects distribution ductwork to an air handling, '
unit. Many buildings use the space above a dropped
ceiling as a plenum.
use, and disposal of chemicals are
important elements of IAQ
management. Air from chemical
storage areas should be exhausted
directly to outdoors, not circulated
through occupied areas of the building.
Air plenums and mechanical rooms
are not proper storage areas. State and/or local school building codes and standards
outline the requirements for proper chemical storage areas. Consult an IAQ
professional regarding these requirements if you suspect improper storage of
chemicals.
These are just a few of the IAQ problems commonly found in schools. Consider
these examples as you conduct your building investigation(s), and seek additional
guidance if you need help to investigate or correct a suspected IAQ problem. Many
potential IAQ problems are relatively straightforward to correct once you recognize
the potential problem. For example, in the case of vehicles idling near an outdoor
air intake, one possible solution would be to relocate the vehicles and prohibit
idling near air intakes in the future. However, some solutions are more complex.
An indoor mold and mildew problem resulting from high relative humidity will
probably not be solved by cleaning the surfaces on which mold and mildew grow. It
will also require correcting or adjusting the HVAC system so that relative humidity
is maintained below the level that promoted mold and mildew growth in the first
place. As you perform the building investigations described in this document, take
note of potential IAQ problems and seek additional guidance if you need help to
investigate or correct a suspected IAQ problem.
2.1 Building Dynamics
A building can be thought of as a dynamic system. Air flows into, out of, and
Within the building change in response to outdoor conditions (e.g., temperature,
wind) and indoor conditions (e.g., doors opening and closing, fan systems cycling on
and off). These air flows, in turn, influence the rate of radon entry, the distribution
of radon within the building, and the rate at which radon is removed by dilution.
2-2
-------
The Indoor Environment and Radon
Air needs both a pathway and a driving force in order to move between two
points. Pathways for air movement can be planned or unplanned. Windows and
air distribution ducts are planned pathways the building designer intended air to
move along these routes. Unplanned pathways for air movement include utility
tunnels, plumbing chases, the hollow interiors of block walls, cracks and holes in
the building structure, and unsealed seams in ductwork. Pathways change when
doors, windows, and air distribution dampers open and close. They also change as
walls are moved, buildings are expanded, and foundations settle over time.
Pressure differences are the driving force behind air movement. Air flows from
areas of relatively higher (positive) pressure to areas of relatively lower (negative)
pressure along any available pathways. As fans move air, they create pressure
differences between rooms and between the building interior and the outdoors. If
the air pressure in ground-contact rooms is lower than the air pressure in the soil
outside a building, soil gas will flow into the building.
a. Air Circulation Patterns
When air is removed from a room, an equal amount of air must enter the room.
When air is blown into a room, an equal amount of air must leave. Whether a
mechanically ventilated room is under negative, positive, or neutral pressure
relative to outdoors depends on the balance between the quantity of air that is
supplied and the quantity that is removed as return or exhaust.
2-3
-------
The Indoor Environment and Radon
a. Negative Pressure
Figure 2-1 illustrates these examples:
In example a): An exhaust fan removes 500 cubic feet per
minute (cfm) of air from a room. This lowers the air pressure,
creating just enough negative pressure to draw 500 cfm of air
into the make-up room through cracks and openings. Air
movement into a room through cracks and openings in the
building is called infiltration. If this room has openings to
earth and radon in the soil, radon will be drawn into the
building.
b. Positive Pressure
In example b): A supply fan blows 500 cfm of air into a room.
This raises the air pressure and creates just enough positive
pressure to push 500 cfm of air out of the room through cracks
and openings. Air movement out of a room through cracks
and openings is called exfiltration. Even if there are
openings to earth and radon is in the soil, soil gas and radon
will not enter as long as the positive pressure is maintained.
This is the principle behind pressurization as a radon
mitigation technique.
c. Neutral Pressure
In example c): A room has both a 500 cfm supply fan and a
500 cfm exhaust fan. Five hundred cfm of air moves through
the room, but the room remains at neutral pressure, (neither
positive nor negative). There is no infiltration or
exfiltration. As long as it is at neutral pressure, this room
should not have a radon problem. However, it is difficult to
maintain an exact neutral pressure balance over time.
Figure 2-1: Air Pressure Relationships
2-4
-------
The Indoor Environment and Radon
In rooms that have no mechanical supply or exhaust, one area can be under
negative pressure while another area is positively pressurized. For example:
A room has steam radiators for heating, but no mechanical ventilation. Warm air rises, creating
positive pressure at the upper level of the room. The warm air exfiltrates outdoors through cracks
and openings high in the walls, in the roof, and at the roof-wall joint. This creates a negative
pressure at floor level and causes the infiltration of an equal amount of air through cracks and holes
(e.g., at the floor-wall joint and through any openings in the slab). If this room lias any openings to
earth and radon in the soil below the foundation, it could have a radon problem.
The example above describes the stack effect, the pressure difference created by
warm air rising. In general, the greater the indoor/outdoor temperature difference
and the taller the building, the stronger the stack effect. Wind also creates pressure
differences. Wind blowing against the walls pressurizes some rooms while
depressurizing others. Wind blowing across the top of a building pulls air upward.
Overall, both wind and the stack effect tend to draw radon into buildings and move
it upward.
Air flow patterns in a large building can be complicated, because pathways and
pressure relationships change as doors open and close and fans cycle on and off.
Comparing the amount of air that is supplied to the amount that is returned or
exhausted will reveal whether air leaks into or out of any particular area. However,
it may be difficult to discover where infiltration air is coming from or where
exfiltration air is going.
EPA researchers have found that many schools tend to run negative (operate
under negative pressure relative to outdoors), increasing the likelihood of radon
problems. Schools (or areas within a school) may run negative under a number of
conditions:
Areas without mechanical ventilation tend to run negative because air
pressures in the building are dominated by wind and the stack effect.
Areas that rely on exhaust fans to draw in outdoor air for ventilation are
depressurized by the operation of the exhaust fans.
Areas such as toilets, kitchens, science laboratories, and darkrooms usually
run negative by design, to keep odors and pollutants out of surrounding
rooms.
Areas that have both supply and exhaust fans will run negative if the total
fan-powered exhaust is greater than the total fan-powered outdoor air intake.
This may occur if:
- the building was not designed to run positive
- energy conservation measures have reduced outdoor air flow by closing air
intake dampers on unit ventilators or air handling units
2-5
-------
The Indoor Environment and Radon
- air handling equipment no longer provides and distributes ventilation air
according to the design
- additional exhaust fans have been installed since the original construction
- filters and/or coils are dirty, reducing air flow
Areas that are pressurized during occupied periods may run negative during
evenings and weekends (due to stack and wind effects), when HVAC systems
are commonly set back or turned off. Radon levels may build up during these
unoccupied periods, then drop again when the HVAC system resumes its
occupied cycle.
Mechanical rooms or other locations containing combustion appliances will
run negative when that equipment is firing, unless there is an adequate
source of outdoor air for combustion.
Pressure relationships are relative. Active soil depressurization, the most
widely-used approach to radon mitigation, works by withdrawing air from the soil
under the building foundation (to create a negative pressure field) and venting it
above roof level. ASD can prevent radon from entering the building as long as the
air pressure generated by the ASD system is lower than the air pressure in any
ground-contact room.
b. Outdoor Air Ventilation
There are many ways to bring outdoor air into a building. Some systems rely on
natural ventilation, using operable windows to regulate the entry of outdoor air;
other systems use mechanical air handling equipment to provide a flow of outdoor
air that dilutes indoor air contaminants and is heated or cooled to maintain comfort
conditions. Mechanical ventilation systems may depend on a large number of small
units (such as unit ventilators) distributed through the building, with an outdoor
air intake at each unit. They may use central air handling units that distribute
ventilation air through ducts and plenums. Many school buildings combine several
approaches to outdoor air ventilation.
The higher the outdoor air ventilation rate (usually expressed as cubic
feet/minute per person, or cfm/person), the more outdoor air is available to dilute
radon and other indoor air contaminants. The volume of outdoor air that a
ventilation system supplies to a space depends on the use of the space. For example,
rooms that contain sources of air contaminants (such as locker rooms or smoking
lounges) require more outdoor air per occupant than offices or classrooms. (See
Table 2-1.)
2-6
-------
The Indoor Environment and Radon
Ventilation standards, such as the American Society of Heating, Refrigeration,
and Air-Conditioning Engineers' ASHRAE Standard 62, describe the outdoor air
requirements for different building types and room uses. Table 2-1 shows the
current ASHRAE recommendations for various areas in school buildings.
Recommended outdoor air ventilation rates have changed over time. From 1936 to
1973, Standard 62 called for 10 cfm of outdoor air per person in classrooms. In 1973,
this quantity was reduced to 5 cfm/person, but in 1989, Standard 62 was revised
again to call for 15 cfm of outdoor air per person. State and local codes do not always
echo the recommendations of the professional organizations (such as ASHRAE)
who develop model standards. Your state's Education Department can help to
identify the codes that applied when your school was designed and the codes or
standards that govern new school construction in your area.
The relationship between the HVAC system and indoor radon can be complex.
A ventilation system that maintains all or part of the building under negative
pressure (such as a ventilation system that includes exhaust fans but no supply fans)
tends to draw in radon-containing soil gas. Increasing the outdoor air ventilation
rate in such a system could increase or decrease indoor radon concentrations,
depending on the size and distribution of below-grade and above-grade openings.
This type of ventilation system can also prevent an ASD system from working
effectively by competing with or defeating the negative pressure developed by the
ASD system.
Even ventilation systems that have mechanically-supplied outdoor air can create
problems for ASD systems if the ventilation system is designed or constructed in a
way that draws soil gas into the building. Examples of features that "mine" soil gas
include:
Return ducts that are routed through earth-floored crawlspaces or utility
tunnels or that are located under the building slab
Air handling units installed with the return side tight against the slab, if there
is also an opening through the slab (e.g., a floor-wall crack or piping that
penetrates the slab) inside the return plenum
Above-ceiling return plenums are located in an area where masonry walls
have open block tops
It is, therefore, important to understand the potential impacts that HVAC
systems and ASD systems may have on each other. Both systems manipulate the
building's air dynamics; installing or adjusting either type of system without
knowledge of how it may affect the other could seriously jeopardize the
performance of the radon control strategy.
2-7
-------
The Indoor Environment and Radon
Application Occupancy Cfm/person
(people/1000
Instructional areas
Classrooms 50 15
Laboratories 30 20
Music rooms 50 15
Training shops 30 20
Staff areas
Conference rooms , 50 20
Offices 7 20
Smoking lounges 70 60
Bus garage: 1.5 cfm per square foot of floor area. Distribution among people must consider worker
location and concentration of running engines; stands where engines are run must incorporate
systems for positive engine exhaust withdrawal. Contaminant sensors may be used to control
ventilation.
Assembly rooms
Auditoriums 150 15
Libraries 20 15
Gymnasiums
spectator areas 150 15
playing floor 30 20
Food and beverage service
Cafeteria 100 20
Kitchen 20 15
Additional airflow may be needed to provide make-up air for hood exhaust(s). The sum of
the outdoor air and transfer air of acceptable quality from adjacent spaces shall be
sufficient to provide an exhaust rate of not less than 1.5 cfm/square foot.
Miscellaneous
Corridors: 0.1 cfm/square foot
Locker rooms: 0.5 cfm/square foot
Nurse's offices (patient areas) 10 25
Restrooms: 50 cfm/urinal or water closet
Table 2-1: Selected Outdoor Air Ventilation Recommendations
SOURCE: ASHRAE Standard 62-1989, Ventilation for Acceptable Air Quality
2-8
-------
The Indoor Environment and Radon
2.2 Radon Mitigation Strategies
Radon control depends on: a) changing pressure relationships to prevent radon
entry (pressurizing the building interior or using ASD to depressurize the space
under the building), b) diluting the radon after it enters the building, or c) an
approach that combines these principles. Strategies that prevent radon entry have
been applied successfully in buildings with a wide range of radon concentrations.
Strategies that use outdoor air to dilute radon after it has entered the building are
most practical if the pre-mitigation radon concentration is only slightly elevated.
Some mitigation approaches use the existing building HVAC system, while
others require the installation of dedicated radon control equipment. For long term
control over the radon problem, any corrective actions must be institutionalized
(incorporated into your normal operations).
a. Radon Mitigation using Active Soil Depressurization
Active soil depressurization (ASD) systems use dedicated radon control
equipment to prevent radon entry. ASD functions by creating a negative pressure
field in the soil beneath the building foundation. Because most buildings have floor
slabs, ASD is also referred to as "subslab depressurization." However, soil
depressurization can also be accomplished in areas without slabs by creating suction
under an installed membrane. As long as the air pressure below the building slab
(or installed membrane) is lower than the air pressure in any ground-contact rooms,
radon cannot flow into the building. If there are any cracks or holes in the slab or
foundation walls, air will be drawn from the building interior into the subslab area.
In a typical ASD design, one or more holes are opened through the floor slab,
and a small pit is dug beneath each slab penetration (see Figure 2-2). Piping (usually
4" or 6" diameter) is installed at each slab penetration and used as ductwork. The
piping runs from the subslab pit to one or more dedicated radon control fans,
chosen for their ability to operate under conditions of high static pressure and
relatively low air flow. The radon control fans operate continuously, drawing radon
from under the slab and exhausting it to outdoors, where it dissipates. Sensors on
the pipe are linked to an alarm system that alerts building operators if the pressure
in the pipe drops, allowing radon concentrations to rise.
2-9
-------
The Indoor Environment and Radon
ASD is the most widely-used method of radon control, and will probably be part
of the mitigation plan for any school with radon concentrations above 10 pCi/L.
The complexity of an ASD design will depend on the characteristics of the
foundation and the subslab material (factors that will be discussed in Section 6: The
Detailed Building Investigation).
ASD offers several advantages:
It is effective regardless of the pre-mitigation radon concentration.
It has been more widely studied and applied than any other mitigation
strategy, and has been proven successful in a wide range of buildings and site
conditions.
The fans used in ASD systems are relatively small, and therefore have only a
minor impact on energy consumption.
The ASD system is not affected by normal occupant activities such as opening
and closing windows.
The disadvantages of ASD are that:
It only affects radon and other soil gases, and will not correct other existing
indoor air quality problems.
Before the ASD system can be successful, it may be necessary to seal large
openings to earth and correct excessive negative pressures in the building.
A large number of suction points may be required in some buildings.
Figure 2-2 illustrates a typical ASD system layout.
2-10
-------
The Indoor Environment and Radon
Exhaust outlet - locate above highest point of roof
and at least 10' from any outdoor air intake
Exhaust fan: Locate so that portions of ducts that are under
positive pressure (i.e., between fan and exhaust outlet) are
outside the building. Provide access for service.
arm (see note below)
Flow sensor
(in duct)
Labels identify the radon control system
and indicate airflow direction
Suction point
Use polyurethane caulk to seal at
the floor penetration
1 Suction pit
Subslab aggregate
Figure 2-2: Active Soil Depressurization
This mitigation technique uses a fan to exhaust air from beneath the slab
so that the air pressure beneath the slab is lower than the air pressure in
the occupied space above the slab. Radon is drawn through the soil into
the low pressure duct and exhausted above the roof. The presence of
coarse aggregate below the slab helps to extend the negative pressure
field.
Note: The alarm will be triggered if the negative pressure field below the
slab weakens or fails. A pressure sensor onflow sensor connected to the
alarm should be installed either in the low-pressure duct or at a hole
drilled through the slab.
2-11
-------
The Indoor Environment and Radon
b. Radon Mitigation Using the Ventilation System
A building's ventilation system can sometimes be adjusted to introduce
additional outdoor air so that radon concentrations are lowered by dilution or by
pressurizing the building to prevent radon entry. For either dilution or
pressurization, the ventilation system must have mechanically-supplied outdoor
air. Figures 7-1 and 7-2 in Section 7 illustrate these approaches to radon mitigation.
Dilution with additional outdoor air can be a successful approach to radon
control if: 1) initial and follow-up tests indicate that the radon concentration is no
higher than 10 pCi/L, 2) occupied areas are not being supplied with enough outdoor
air for ventilation, 3) the existing ventilation system has sufficient capacity to
increase the flow of outdoor air, and 4) the increased outdoor air flow does not
introduce levels of pollutants or moisture that could create IAQ problems.
A dilution-based mitigation design requires careful evaluation of outdoor air
flows into every affected area of the building. Dilution will only work if outdoor air
mixes thoroughly with room air. The control system must be arranged so that
adequate outdoor air flows into the building whenever it is occupied. If outdoor air
intake dampers are closed during unoccupied periods, the occupied cycle should
start early enough to lower radon to levels below 4 pCi/L before occupants arrive.
Dilution offers several advantages as a mitigation approach:
It offers an alternative in buildings where ASD is not appropriate.
It makes use of the building's existing ventilation system.
In most cases, increasing the flow of outdoor ventilation air will improve
general indoor air quality.
Even if dilution alone cannot reduce radon below 4 pCi/L, it may still be
valuable as a means of supporting other radon mitigation measures.
There are also disadvantages:
Dilution alone is not likely to succeed if pre-mitigation radon levels are
higher than 10 pCi/L.
Outdoor air flows must be maintained continuously during occupied periods
in order to control the radon concentration. If the freeze protection system
shuts down outdoor air flows during a period of cold weather, radon is likely
to approach its pre-mitigation levels.
If a ventilation system has been poorly maintained in the past, it will require
financial commitment and policy changes to achieve reliable, long-term
control of the radon problem.
2-12
-------
The Indoor Environment and Radon
The introduction of additional outdoor air may increase energy costs. The
amount of the energy penalty will vary from school to school.
Radon concentrations may rise to high levels when the ventilation system is
not operating (for example, during the "night" or "unoccupied" cycle).
In some cases, ration control and improved indoor air quality canbe achieved without increasing
energy costs, simply by adjusting air distribution within the building. Researchers have found
scnools in whicK the oritdoor air intakes are-blocked off, but large exhaust" fans are removing the
sarries amount of air that originally entered thrdugh the outdoor air intakes. While classrooms
in these schools are not supplied with enough'outdo'dr ventilation air/ large 'quantities of" '
outdoor air are being drawpa through exterior doors and corridors to replace the air removed fay
the exhaust fans. * ' , f
Pressurization of the occupied space is, in theory, an effective way to prevent
radon entry. However, it is not a practical mitigation strategy for most schools. This
mitigation approach is best suited to tightly-constructed buildings with central air
handling systems. The building's existing ventilation system must be adjusted (e.g.,
by increasing the supply air flow and/or decreasing the return air flow) until any
room with a radon problem is pressurized relative to the subslab.
The advantages of pressurization are that:
It can be effective regardless of the pre-mitigation radon concentration.
It makes use of the building's existing ventilation system.
It can be used to support the operation of ASD systems in buildings that have
high pre-mitigation radon concentrations but are poorly suited to ASD.
If the existing HVAC system already introduces adequate outdoor air to meet
ventilation needs, it might be possible to pressurize a building without
increasing energy costs by reducing the flow of return air.
However, pressurization has some disadvantages:
For radon control, the building must run neutral to slightly positive
whenever the building is occupied. This requires a clear understanding of
building dynamics and good control over both the quantity of outdoor air
blown into the building and the amount of air leaking out of the building.
Control of the outdoor air flow would be impractical for schools with
multiple small units (such as unit ventilators), and sealing leaks could be a
major expense in some buildings.
2-13
-------
The Indoor Environment and Radon
As with dilution, outdoor air flows must be maintained continuously during
occupied periods in order to control the radon concentration. If the freeze
protection system shuts down outdoor air flows during a period of cold
weather, radon is likely to rise above 4 pCi/L.
Occupants may unintentionally defeat a pressurization system by opening
doors or windows or operating locally-controlled exhaust fans (e.g., kitchen
range hoods, paint spray booths).
As with dilution, any radon mitigation system that introduces additional
outdoor air may also increase energy costs.
c. Sealing
Sealing openings to the ground is rarely successful as a stand-alone solution to
radon problems. It is impractical to seal every potential radon pathway in an
existing building. If there is a pressure difference to propel it, radon can (and will)
move through openings that are invisible to the human eye. A radon atom can fit
into a tiny floor crack as easily as a golf ball can fit into the Grand Canyon. However,
it may be necessary to seal large openings so that other radon mitigation strategies
can be successful. See pages 4-5 and 4-6 in Section 4.2 for additional discussion of
sealing.
2-14
-------
Evaluating and Correcting Radon Problems
3.0 Evaluating and Correcting Radon Problems
This section presents a flow diagram showing the radon mitigation process in
school buildings and provides guidance in performing the initial investigation. The
flow diagram is intended to promote understanding of the investigative process and
how this process leads to selecting the best mitigation approach for a particular
building. Some pointers are provided to help select the team who will perform the
initial investigation. Detailed guidance is then presented, describing how the initial
investigation is performed.
'Comtttissioftmg'is a^process trtat
involves extensive testing of*"
-> system performarae-tinder
different operating conditions.- .
' Buildings should be < '
commissioned after construction'
is completed andbefore,
occupants move in.
Results of EPA's school radon survey indicate
that schoolrooms with elevated radon
concentrations are likely to have concentrations
between 4 and 10 pCi/L. At the same time, EPA field
researchers have found that schools with elevated
radon levels are often undersupplied with outdoor
ventilation air (that is, the supply of outdoor air is
not enough to meet current standards). Inadequate
outdoor air ventilation can occur for reasons such
as: poor initial design, lack of system
commissioning, and/or lack of preventive maintenance. Inadequate maintenance
of HVAC systems is common due to budget constraints and lack of in-house HVAC
expertise. Compounding the problem, the outdoor air intakes of many schools have
been partially or completely closed in an attempt to save energy. EPA's work in
schools suggest that many, with radon levels between 4 and 10 pCi/L, may be
mitigated by restoring or modifying the building's ventilation system.
Because adequate outdoor air ventilation is frequently lacking, EPA recommends
that a ventilation evaluation be performed as a first step toward mitigating radon.
This evaluation will provide you with a better understanding of how well your
HVAC system is functioning to provide outdoor air ventilation and whether the
ventilation system may be used - alone or in combination with an ASD system to
reduce radon concentrations.
3.1 Problem Assessment and Strategy
This document presents a step by step investigative process that will enable you
to determine the best radon mitigation strategy for each building you are mitigating.
Figure 3-1 is a flowchart that graphically illustrates the steps you will be taking as
3-1
-------
Evaluating and Correcting Radon Problems
you proceed through this document and perform these investigations within the
building. This flowchart will serve as your "map" to radon mitigation.
Unfortunately, there is no single radon mitigation strategy that is applicable to all
school buildings. Comprehensive building investigations and diagnostics are the
only effective way to determine what mitigation strategy to implement. Radon
concentration, entry, and distribution are dependent on the indoor air dynamics (see
Section 2.2). A building's HVAC system is capable of drastically changing these
dynamics, and its potential influence must be understood.
The Initial Investigation described in Section 3.4 begins with an examination of
the building and its ventilation systems. The investigation team will identify
ventilation-related HVAC deficiencies and large openings to earth that may be
radon entry points. The Initial Investigation also provides an opportunity to begin
collecting information that will be of interest if a detailed investigation is necessary,
such as: 1) whether the way the ventilation system operates could interfere with the
effectiveness of a radon mitigation strategy, and 2) how correcting ventilation
deficiencies may affect radon concentrations.
The Detailed Investigation (Section 6) requires more technical skills and
equipment than the initial investigation and typically involves consultants, such as
radon mitigation contractors and mechanical engineers. Section 6 describes the
diagnostic techniques used by building investigators, presents the basic components
of radon mitigation systems, and discusses how information collected during the
investigation helps in selecting a mitigation strategy. This information will help a
"team leader" select and direct consultants.
Look over Figure 3-1 and refer to it often as you proceed through this document.
Some of the terms in the figure, as well as the descriptions of the diamond-shaped
boxes that follow, may seem unfamiliar to you now, but will be defined and
discussed in detail in the sections ahead.
3-2
-------
Evaluating and Correcting Radon Problems
| Start: Radon 4 pCi/L or higher |
*
I Sections 3-5: Initial Investigation |
Sections 6-9:
Detailed
Investigation
Were
:-mitigation\ Yes
Cradon levels over>
lOpCi/L
Evaluate potential
for ventilation-based
mitigation strategy
Restore ventilation system: Correct
malfunctions and increase outdoor air
to equal or exceed design quantities.
Were
re-mitigationV Yes
radon levels over
Did
restoration
increase outdoor
air enough to
retest radon
levels
Retest radon levels
don
retest X No
results below
4pCi/L
Consider
dilution
alone or in
combination
^-
Consider
pressurization
alone or in
combination
1
Implement
strategy
Consider
ASD
alone or in
combination
Institute a long-term
Radon Management Plan
Figure 3-1: School Mitigation Flowchart
3-3
-------
Evaluating and Correcting Radon Problems
The following discussion is intended to help you work with Figure 3-1, the
School Mitigation Flowchart. The diamond-shaped boxes on the left correspond to
the "decision" boxes on the flowchart. These decision boxes will be discussed in
greater detail in the remainder of the document. The description provided below
explains the relevance of each decision point and will assist you in seeing how all
the pieces lead to the selection of an effective radon mitigation strategy.
Were
ventilation
malfunctions
found?
INITIAL INVESTIGATION
Review the results of the Initial Investigation. Did you identify
ventilation system malfunctions? If so, it is advisable to restore
the entire ventilation system to proper functioning, giving
priority to equipment that serves areas with elevated radon
concentrations. (See Section 4).
If you did not find any ventilation system problems, your school
mechanical system may be supplying roughly the amount of
outdoor ventilation air that is described in the plans and/or
specifications. Pages 3-20 to 3-22 describe how to use the
mechanical plans and mechanical schedules to discover the
design outdoor air ventilation rates. You will need to obtain
measurements of air flows if you want to know how much
outdoor air is actually provided to any area. Section 6.3 3c of this
document describes how to evaluate outdoor air flow quantities
(see pages 6-30 to 6-34).
The current American Society of Heating, Refrigeration, and
Air-Conditioning Engineers (ASHRAE) standard (now being
adopted into many codes) calls for at least 15 cubic feet per
minute (cfm) of outdoor air per person in classrooms. Most
existing school mechanical systems were designed to provide
less than this amount. Pre-1973 schools were often designed to
provide 10 cfm/person of outdoor air; after 1973, most were
designed at 5 cfm/person. NOTE: The ASHRAE standard is for
minimum outdoor air volumes.
If the outdoor air ventilation rate is below 15 cfm per person in
any occupied space, EPA recommends increasing the outdoor air
flow to a minimum of 15 cfm/person. This will tend to lower
radon concentrations by diluting the radon with outdoor air.
3-4
-------
Were
pre-mitigation
radon levels
Evaluating and Correcting Radon Problems
Throughout this document, you will see the term pre-mitigation
radon level. This term refers to the radon concentration before
taking corrective action, and is either: 1) the averaged result of
two short-term tests, or 2) the result of the long-term follow-up
test. If your pre-mitigation tests showed radon concentrations no
higher than 10 pCi/L, it may be possible to treat the radon
problem successfully by correcting gross problems with the
HVAC system and sealing large openings to the ground (such as
sumps). Corrective actions that can be identified by school
personnel without the assistance of outside consultants may be
enough to resolve the radon problem and may also improve
indoor air quality.
Where radon concentrations are above 10 pCi/L, changes in
ventilation alone are unlikely to provide dependable, lasting
control over the radon problem. In most cases, ASD (alone or
combined with a ventilation-based strategy) will be the preferred
mitigation approach. A Detailed Investigation, generally
involving outside professionals, will be needed to evaluate the
building and develop a detailed mitigation plan (see Section 6).
The 10 pCi/L level used here is not meant as an absolute
dividing point. It is intended to help you in selecting the
mitigation strategy that will be most effective in reducing radon
concentrations now and in the future. EPA's research and
demonstration work has shown that radon levels below 10
pCi/L can be reduced through the controlled introduction of
outdoor air by a properly functioning HVAC system. On the
other hand, levels above 10 pCi/L usually require a more
aggressive approach, such as ASD.
EPA does not intend to exclude any proven mitigation approach
from consideration. Under some circumstances, ASD can be the
most practical approach to correcting low-level radon problems
(for example, in areas that are already well ventilated or in areas
that have no mechanical ventilation). ASD may also be needed
if initial ventilation improvements do not reduce the radon
concentration below 4 pCi/L. Some areas with radon levels over
10 pCi/L might be corrected with improved ventilation.
However, with higher radon concentrations, it may not be
possible to achieve long-term, reliable control of the problem
using a ventilation-based mitigation approach, and the health
3-5
-------
Evaluating and Correcting Radon Problems
Did
restoration
increase outdoor
air enough to
retest radon
levels
Radon
retest results
below 4
pCi/L?
consequences of failure become more serious. Nonetheless,
ventilation improvements made in an attempt to reduce radon
concentrations are likely to generally benefit indoor air quality
and assist the efficient operation of an ASD system.
If the Initial Investigation discovered areas in which outdoor air
ventilation was drastically reduced, and if the restoration work
has increased outdoor air flows to at least the quantities specified
in the original design, then radon concentrations that were
below 10 pCi/L may have been reduced to less than 4 pCi/L.
Retesting for radon in these areas may (or may not) save you the
effort and expense of a Detailed Investigation. Consider the
following examples:
1) The outdoor air damper on a 750 cfm unit ventilator is closed
and the damper actuator is disconnected. Investigators assume a
leakage rate of 75 cfm (5%) through the damper. They decide
that, if the damper and controls are restored to provide at least
300 cfm of outdoor air during occupied periods, the four-fold
increase in outdoor air flow is very likely to lower radon from
the pre-mitigation level of 10 pCi/L to below 4 pCi/L. Retesting
after restoration seems to be a good investment.
2) The outdoor air damper on a unit ventilator appears to open
and close, but the filter is dirty. The unit is probably not
introducing as much outdoor air as it should. However, it is
hard to predict how a clean filter will affect the indoor radon
level. Actual air flows should be measured during a Detailed
Investigation.
If a radon retest shows that radon is below 4 pCi/L in all areas,
institute a long term radon management plan as described in
Section 9. If some areas remain above 4 pCi/L, conduct a
Detailed Investigation as described in Section 6.
3-6
-------
Were
pre-mitigation
radon levels
Evaluating and Correcting Radon Problems
DETAILED INVESTIGATION
If pre-mitigation radon levels were over 10 pCi/L, ASD will
probably be needed to keep indoor radon levels consistently
below 4 pCi/L. Many schools will probably require a combined
approach. Figure 6-4 on page 6-12 presents a flowchart for
evaluating the potential for ASD. If conditions are not favorable
for ASD, pressurization or dilution can support the operation of
an ASD system.
If pre-mitigation radon levels were less than or equal to 10
pCi/L, a ventilation-based mitigation strategy may be able to
maintain radon below 4 pCi/L. Dilution and pressurization will
need to be evaluated to determine whether a ventilation strategy
is feasible.
Good
indicators
for
dilution
Use the equation below to evaluate the potential for dilution:
(lowering radon levels by introducing additional outdoor air).
For meaningful results, use actual measured air flows. Pages 6-6
to 6-7 and 7-11 to 7-13 describe dilution in more detail.
Estimated final radon level = Pre-mitigation radon level x Initial outdoor airflow
Final outdoor airflow
Notes:
1) If your HVAC system relies on exhaust fans to draw outdoor
air into the building, increasing the outdoor air ventilation rate
will increase dilution, due to the increased makeup air, but also
cause the building to operate under a stronger negative pressure
relative to outdoors. The effect on radon levels is unpredictable.
2) Outdoor air flow must not exceed the ability of the HVAC
equipment to condition (heat or cool) the air. The amount of
dilution depends on the flow of outdoor air, so radon
concentrations will rise when outdoor air dampers close to their
minimum position and when fans cycle off.
3) If you would have to raise the outdoor air flow above 15
cfm/person to bring radon below 4 pCi/L, dilution is probably
not a practical mitigation approach.
3-7
-------
Evaluating and Correcting Radon Problems
Favorable indicators for pressurization (increasing indoor air
pressure to prevent radon entry) are:
the subslab material is low permeability, (e.g., sand or clay)
there are many obstacles to ASD, such as inaccessible slab
leaks or interior subslab footings
the building shell is tight or can be easily tightened
the building has a fan-powered outdoor air supply (with
or without fan-powered exhaust) and sufficient heating
and/or cooling capacity
radon concentrations are below 10 pCi/L (see below)
If the results of post-mitigation testing show radon levels below
4 pCi/L, institute a long-term radon management plan. If the
results are 4 pCi/L or higher, troubleshoot the mitigation system
and retest.
3.2 The Initial Investigation Team
EPA recommends organizing a building investigation team, including such
members as maintenance personnel and the school district's HVAC specialist(s),
who may be either a member of the district staff or an outside contractor such as a
mechanical contractor, control technician, or test and balance (TAB) contractor.
Even though it may appear that a single individual has a complete understanding of
your school building and how it functions, the use of a team approach promotes
discovery of new information and full consideration of your alternatives. The
building investigation team should include someone who is familiar with the
building structure, HVAC system, and operating and maintenance practices. Equally
important, some member of the team should have the authority and knowledge to
safely remove HVAC access panels for inspection and manipulate the HVAC
control system so that the effect of HVAC operation on air pressure relationships
can be determined.
Ideally, school personnel included on the team should:
* have time to allocate to the radon issue
* be well adapted to training
3-8
-------
Evaluating and Correcting Radon Problems
accept the administrative responsibility for seeing the job is well done
have the ability to maintain accurate records
Potential Team Members and What They Cart Contribute to fhe Initial Investigation*
; School administration representative'- fcan serve as a liaisbnTwith school ฐ ' , -
^ superintendent's office, board of education, and other djstripjt'declsibninakers; ; "
could also be^tnedia contact person ^ ' ฐ f ,,''*-
* " FaciHtystalfiinemberCsJ^famillar-wilh school mechanical system design,
_ pperatibn4ฐartd maintenance; can provide access" to equipment and charige'contcols
^ "" ' " " '"''"
,, ,,
, The schooFdistrict'sHVAC specialist j(this may be an outside cpntractor>' "
Teacher/staffrepresentative -"Baison with other staff members; can help build
support for mitigation effort' . '" ';- - -? *> * "" ,"
'PTA representative - Bauson 'with other parents; can help to"buMd support for .
> mitigation, effort ' ..",' ฐ ,, ,. -
This photograph shows a building
investigation team organized by
EPA. Team members gather to
review the architectural and
mechanical plans and discuss the
building design before beginning
the walkthrough investigation.
If a detailed investigation (described in Section 6) is required, additional team
members may be needed. Scnool personnel with little training or experience in
radon reduction should use experienced EPA-listed or state-certified radon
3-9
-------
Evaluating and Correcting Radon Problems
mitigation contractors to gain the advantage of their expertise and specialized
knowledge of local problems. EPA recommends the use of firms whose individual
representatives have met the requirements of the EPA Radon Contractor Proficiency
(RCP) program. Listings of these contractors can be obtained from your state radon
office; some states also operate their own certification programs. Ideally, you should
use a radon contractor with proven experience in school buildings similar to yours,
or at minimum experience in large, non-residential buildings.
The participation of a registered engineer or architect may be required on work
affecting mechanical systems, structural components, and life and safety codes. A
mechanical engineer who specializes in HVAC systems is particularly important if
your radon contractor is not familiar with school HVAC systems.
EPA's four Regional Radon Training Centers (RRTCs), as well as a number of
private vendors, offer a range of training courses in radon measurement and
mitigation. See Appendix B for more information.
3.3 Evaluate and Map Your Radon Test Results
Before starting to work with the radon test results, make certain that you are
confident in those results. Ask yourself the following questions:
If the measurements were performed by an outside contractor, was the
company listed with EPA's RMP program (or state certified, in states that
have certification programs)?
If the measurements were performed in house, were the EPA protocols
followed?
Did the school district receive data from all of the detectors?
Were HVAC operating conditions maintained as intended during the test
period?
If the school district is not confident that the radon testing was performed in
accordance with EPA's Radon Measurement in Schools - Revised Edition, consider
repeating some or all of the tests.
Check your results to see whether there were quality control or quality assurance
problems in the analysis of your measurement devices. Radon Measurement in
Schools - Revised Edition (see Appendix B) describes the use of blanks (test devices
that are sent for analysis without being exposed) and duplicates (additional test
3-10
-------
Evaluating and Correcting Radon Problems
devices placed in the same location over the same time period) for quality
assurance/quality control. For duplicate pairs where the average of the two
measurements is greater than or equal to 4 pCi/L, the results should not differ by
more than 25%. Consistent failure in duplicate agreement should be investigated.
Blanks that fail to yield results at or near 0.0 pCi/L (e.g., 0.5 pCi/L) indicate that the
manufacturing, shipping, storage, or processing of the detector may have affected
the accuracy of your measurements.
One of the most valuable ways to record information collected during a building
investigation is to take notes on a small
floorplan of the building (typically a 8 1/2" x
11" plan), referred to in this document as a
working floorplan. Taking notes on a
floorplan will help you to develop an
understanding of the spatial relationships
involved in radon distribution, air flow
patterns, and the use of ventilation
equipment in your building. This document
presents a series of example floorplans you
can refer to as you take notes on your own
working floorplan.
Start your buildlrig Mvesfigafioaby -
obtaining a small floorplatri of youฃ
buildings-such as a fire escape '' *ฐ
.floorplan. This is called your working
ftootplan to disttaguislvit from large -
.architectural/mechanical plans., Take
notes on, the working floorplan as'you ;"
collect information.'0,* -.', .", '; '-%
"The te!$n$re-mitigation melon level refers to the radori.
concentration before taking"corrective action, and is either: 1)
the .averaged result of two snortjterm tests,! or 2) the result of the
long-term follQw-up test, Fof example, if the initial test'result
> was 10 pCi/L arid the short-term follow-up test result was 4 - *
spCi/L/the p^e~rnitigation'radon;level would be; \ '\
If there are no signs of
problems with the radon
measurements, map your
pre-mitigation radon levels
onto your working
floorplan. It may be helpful
to shade or color this radon
map to show areas of high,
medium, or low radon
concentrations. For
example, you may want to
leave rooms which were not tested white on the map, and choose separate colors or
shading patterns for rooms that tested below 4 pCi/1, between 4 and 10 pCi/L, and
over 10 pCi/L. Sample Working Floorplan 1 provides an example.
Radon levels in non-residential buildings often vary widely from room to room.
Your radon map may reveal patterns of increased radon levels, including "hot
spots" that could become a focus for later diagnostic and mitigation work. Patterns
of elevated radon concentrations may correspond to factors such as the location of
radon entry points, the HVAC system design or operation, or the wind direction
3-11
-------
Evaluating and Correcting Radon Problems
during the test period. Variations between rooms or zones can sometimes be
explained by differences in ventilation rates or air pressure relationships that are
caused by the mechanical systems. A pattern of consistent radon levels throughout
a zone served by a single air handling unit may indicate that the ventilation system
in that area is "mining" and distributing radon (see pages 6-15 and 6-16 for more
information).
If the pre-mitigation test results show radon levels below 4 pCi/L in most of your
building, you may want to confine your investigation to rooms with elevated radon
concentrations and the mechanical systems that provide ventilation air to those
elevated rooms. However, a building-wide inspection is a practical first step in
improving preventive maintenance and overall air quality. EPA recommends
including the entire building in the initial investigation, so that all HVAC system
deficiencies can be identified and corrected.
3-12
-------
Evaluating and Correcting Radon Problems
Sample Working Floorplan 1
3^-^%ฃ
:^MCt *?'*ฅ*''' -"" "tff&^A..
%|Library/p??r
3&&*g j. :^ซA*
4H1q
>*tffo " ? ^*J* d
-\
-------
Evaluating and Correcting Radon Problems
3.4 Initial Investigation
The scope of the Initial Investigation depends on the capabilities of the
investigation team and the amount of work you choose to accomplish before
conducting a detailed investigation. At minimum, EPA recommends using the
Initial Investigation to identify malfunctioning ventilation equipment, then
restoring the ventilation system to proper functioning before conducting a Detailed
Investigation.
The team leader should read Section 6 to understand the elements of the
Detailed Investigation, then plan an investigation strategy that makes best use of the
skills and availability of team members. While the team is examining the
construction documents and inspecting the building, it may make sense to get a
head start on the Detailed Investigation by collecting information, such as:
1) locations of large openings to earth - sealing these openings may help to reduce
radon entry
2) areas where the outdoor air ventilation rate (either as specified in the design or
as the building is operated), is lower than current recommendations these
areas may be candidates for mitigation using dilution
3) areas that are designed to operate under negative pressure -- these areas may lie
radon entry points
4) factors that are key to ASD (such as foundation types, sub-slab fill material, etc.) -
if this is accomplished during the initial investigation, it can save time during
the detailed investigation
Consider the original building and each addition as if they were separate buildings,
because differences in design, construction, and operation can produce very different
air and radon distribution patterns. Pay particular attention to the ventilation units
that serve rooms with elevated radon, and include all of the rooms served by those
units. This means that, if a single air handling unit or general exhaust fan serves
the entire building, the entire building should be inspected as a part of the radon
investigation. Remember, by including the entire building in the Initial
Investigation, you may identify HVAC system deficiencies that are causing
discomfort or air quality problems.
3-14
-------
Evaluating and Correcting Radon Problems
The one-story wing extending to
the right is an addition to the
original building. Investigators
should treat the original building
and the addition as two separate
buildings.
The Initial Investigation can be divided into two parts, the review of building
plans and the walkthrough inspection. After a review of the building plans and
other related documents, investigators compare their understanding of the building
design to the actual conditions and identify radon entry points and HVAC system
deficiencies.
2.
INITIAL INVESTIGATION
Review the building plans
a. Create an inventory of HVAC equipment within the building
b. Understand the intended design of the HVAC system
c. Identify openings to the ground that may allow soil gas entry
d. Identify foundation types and design (intended) subslab fill material
Conduct a walkthrough inspection
a. Evaluate the condition of the ventilation system
b. Confirm soil gas entry at openings to the ground
3-15
-------
Evaluating and Correcting Radon Problems
1. Review the Building Plans (Initial Investigation)
Testing and balancing involves testing and ,
adjusting the HVAC system so that airflows*
conform to design specifications. See Section ,
9, page 9-4 for more information.
Construction documents such as specifications and architectural and mechanical
plans, if available, show how the building was originally designed to operate.
Collect and examine all available
architectural and mechanical plans,
equipment manuals, specifications, test
and balance reports, and other
documentation. "As-built" plans, if
available, should show changes that were
made during construction. AHERA
(Asbestos Hazard Emergency Response
Act) management plans may provide the
most up-to-date floorplans, heating zone information, and
remodeling/modification plans. AHERA plans can also alert inspection teams to
areas where special safety precautions are required.
The plans and specifications show how your building might function under
ideal conditions, if all equipment were properly installed and maintained. This
information can help to establish the limits of performance that can be expected of
the existing equipment. For example, if your unit ventilator coils only have
enough capacity to condition 100 cfm of outdoor air, then a plan to dilute radon
with 250 cfm of outdoor air would involve more work than merely opening an
outdoor air damper.
It is important to understand the designer's control strategy the strategy by
which various fans and dampers operate - in order to understand a radon problem
and how the HVAC system might be used to fix it. Information about the designer's
intentions is available from the specifications and mechanical equipment schedules.
During the walkthrough inspection, you will see how the building actually operates.
If architectural/mechanical plans and specifications are unavailable, much of
this information can be obtained during the walkthrough inspection. However,
you should attempt to find the building plans, if possible. Some of the information
they contain is time-consuming and expensive to collect by any other means, but
necessary for a complete understanding of the building's air dynamics.
3-16
-------
Evaluating and Correcting Radon Problems
i. Create an inventory of HVAC equipment within the building
^^-^i^.^._
An inventory of HVAC equipment helps to ensure a thorough inspection of the
building. When reviewing HVAC plans, you may discover exhaust fans or other
small items of equipment that have been forgotten because they are located in
remote or inaccessible locations. These items may cause radon or other IAQ
problems if they are overlooked during maintenance.
Note the location and air volume capacity of each item of air handling
equipment, including both total cfm and outside air cfm if available. This
information can be found on mechanical equipment schedules such as the example
in Figure 3-2. Mechanical equipment schedules are usually found on the
mechanical plans, and are sometimes reproduced in the mechanical specifications.
If you are aware of locations where actual building conditions are different from
the design shown on the plans, note those locations on your working floorplan.
There may be items of equipment on the plans that were never installed or were
installed in a different way than indicated on the plans. Update the inventory
during the walkthrough inspection. (If you are not directly responsible for
maintaining the HVAC equipment, use the walkthrough as an opportunity to talk
with the individuals who are. Their input can contribute a great deal of
information.)
3-17
-------
Evaluating and Correcting Radon Problems
MECHANICAL FLOOR PLAN (partial)
OA louverOA louver.
18"x18\
325 cfm\
.18" x 18"
'325 cfm
6"x8"
18" x 18"
300cfnr*>
18"x18"
transfer to above
> enum
018" x 18" 200 cfm
18" x 18"
30Ocfm
16"x14"uptoAHU-1
gravity relief vent
14"x16%18" x 18"
425 cfm
303 18" x 18" 0
250 cfm
6"x8"
18" x IS'1 0
25Ocfm
n on roof
ป - -6" 0
UV-2 18" x 18".
lOOOcfm 325
supply
UV-2
1000 cfm
supply
18" x 18"
425 cfm
-18" x 18"
300 cfm
18" x 18" 200 cfm
6" 0 to fume hood
150 cfm
8" 0 up to E-4
3f
to fume hood
150 cfm
OA louver
O A louver
up to E-5 on roof
16"x14" up to AHU-tA
r 425 cfm
up uu t--i-> <
KEY: [X] supply \/\ transfer \jH exhaust UV= unit ventilator AHU = air handling unit
^"^ E = exhaust fan 0 = round duct
MECHANICAL EQUIPMENT SCHEDULE (partial)
x 18"
325 cfm
UNIT
NO.
UV-1
UV-2
AHU-1
AHU-2
LOCATION
CLASSROOMS
CLASSROOMS
SCIENCE 301
LIBRARY 302
SA
CFM
750
1000
1250
1250
MINOA
CFM
200
250
400
400
HEATING COIL HW@
EATฐF
59.8
45
57.4
LATT
102.9
9O
90
MBH
46.7
61
44.1
GPM
2.4
3.1
4.1
2.9
MOTOR
HP
1/8
1/8
1/8
V
120
120
120
0
1
1
1
1
NOTES
1
1
2,3
1
y\\J \ &C?* I. t-*r\ป I * ปปi I i * iviiii. v-/ ! ซ-- ซ-'*' \ซ" ป '
2. OUTDOOR AIR DAMPER NOT LOCKED OUT BELOW + 35ฐF
3. INTERLOCK WITH EXHAUST FAN E-5 . .
S A = supply air MIN O A = minimum outdoor air (cfm) E AT = entering air temperature
LAT = leaving air temperature MBH = thousand BTU/hour GPM = gallons/minute
HP = horsepower V = volts 0 = phase
Figure 3-2: Typical School Mechanical Plan and Equipment Schedule
The mechanical plan shows the intended airflows into and out of each room, thus revealing which rooms are designed
to operate under negative, positive, or neutral pressure. The mechanical equipment schedule shows minimum
outdoorair flows for each piece of ventilation equipment. Using the equipment schedule and the room population,
it is possible to calculate the intended outdoor air ventilation rate in cfm/person. Exhaust fans (such as E-4 and E-5 in this
example) are typically described in a separate schedule. CAUTION: Construction documents reveal the designer's intent
They do not necessarily show the way the building was constructed or is operated.
3-18
-------
Evaluating and Correcting Radon Problems
b. Understand the intended design of the HVAC system
1
Mark your working floorplan to show:
ventilation zones (the areas served by each air handling unit or unit ventilator)
areas designed to operate under negative pressure
areas that are not supplied with enough outdoor ventilation air to meet current
standards
Which rooms operate under negative pressure by design?
On your working floorplan, mark areas that are designed to operate under
negative pressure with a "-" sign (see Sample Working Floorplan 2, page 3-23).
You can assume that an area is designed to run negative if: 1) it is on the lowest
floor and has no mechanical ventilation or 2) if it is mechanically exhausted but has
no mechanically supplied ventilation. You can assume that an area is designed to
run positive if it has mechanically-supplied ventilation and no mechanical exhaust.
If a space has both supply and exhaust (or return) ventilation, it may run negative
or positive, depending on the net air flow and the airtightness of the space.
Bathrooms, kitchens, smoking lounges, locker rooms, darkrooms, laboratories
with hoods, industrial arts areas, art rooms, and chemical storage rooms are
generally designed to run negative, using exhaust fans to confine and remove odors
or contaminants. Pay particular attention to the design of these and other "special
use" areas. For classrooms, you can save effort by checking "typical" designs in each
section of the building rather than evaluating the plans for each individual room.
A room or zone is designed to run positive if:
Supply cfm > (Return cfm + Exhaust cfm)
A room or zone is designed to run negative if:
Supply cfm < (Return cfm + Exhaust cfm)
Note: * _
O C ซ * * C cซ
In these forraulas/'supply"' m^arts -Sie
total quantity of ait mechanically
;blown irjia fee space, "f
means "less, than," '
3-19
-------
Evaluating and Correcting Radon Problems
The same room may have supply diffusers, return grilles, exhaust fans or any
combination. Mechanical plans generally show the intended air flow through
registers, grilles, and diffusers, while mechanical equipment schedules indicate the
design capacities of air handlers and unit ventilators.
ROOM
SCIENCE 501
LIBRARY 302
CLASSROOMS 303., 305
CLASSROOMS 304,306
PLANNED AIR FLOWS (CFM)
SUPPLY
1250
1250
1000
750
RETURN
850
&5O
750 2
550 2
EXHAUST
500/SOO1
DESIGN AIR
PRESSURE
Supply- (Ret. + Exh.)
100/400 cfm negative
4OO cfm positive
250 cfm positive
ZOO cfm positive
1 E-5 operates constantly (50O cfm exhaust), E-4 operates as needed (additional 300
cfm exhaust)
Return cfm = supply cfm - minimum outdoor air cfm
Figure 3-3: Design Air Pressures
This chart was created using the information presented in Figure 3-2. Note that air leaving classrooms 303,
304,305, and 306 through the transfer grilles does not count as return air, because it is not being returned
to an air handling unit, and does not count as exhaust air, because it is not moved by an exhaust fan.
WJmt areas, if any, are inadequately supplied with outdoor air?
EPA researchers have found underventilation problems (i.e., levels of carbon
dioxide which may indicate the accumulation of indoor air contaminants) in areas
where the design outdoor air flow is less than 15 cfm/person. As you read this
section, mark your working floorplan to indicate areas in which the outdoor air
supply is less than 15 cfm/person (see Sample Floorplan 2). If both the initial
outdoor air ventilation rate and the pre-mitigation radon concentration are low
enough, it may be possible to dilute radon below 4 pCi/L by increasing the supply of
outdoor air.
1. Where outdoor air is supplied by operable windows instead of fans, outdoor air
ventilation rates change as the windows are opened and closed. These areas are
likely to have less than 15 cfm/person of outdoor air ventilation, at least some of
the time (e.g., during unpleasant weather). Mark your working floorplan to indicate
3-20
-------
Evaluating and Correcting Radon Problems
where operable windows are used for outdoor air ventilation. Check during the
walkthrough inspection to make sure that the windows are still operable.
2. In areas with mechanically-supplied ventilation, you can estimate the rate of
outdoor air flow to evaluate the adequacy of outdoor air ventilation. Unless the
HVAC system is very well maintained and is periodically tested and balanced, actual
air flows may be quite different from the design. However, you can begin to assess
the situation by making a quick estimate of outdoor air flow for a few "typical"
classrooms. Select one or two classrooms from each area of the school, making sure
to include rooms from the original building and any additions. If elevated radon
was only found in a small number of rooms, use those rooms.
For each room, collect the following information:
the number of occupants
the outdoor air flow rate
Number of occupants
For the number of occupants in a classroom, use the larger number of: a) the largest
group of occupants present during a normal day, or b) the number of desks.
In assembly areas where the occupant population varies widely (such as
auditoriums, gymnasiums, and libraries), it may be difficult to decide what number
of occupants to use. Ventilation equipment in assembly areas should be restored to
provide at least as much outdoor ventilation air as was provided in the original
design.
Outdoor air flow rate
If a recent test and balance (TAB) report is available, use the measured air flow
obtained when the outdoor air damper was at minimum setting. If you do not have
a recent TAB report, use the minimum outdoor air flow as shown on the
mechanical plans or mechanical equipment schedule.
When you know the number of occupants and the outdoor air ventilation rate,
the outdoor air ventilation rate in cfm/person can be estimated using the following
equation:
Outdoor air ventilation rate (cfm/person) = outdoor air flow fcfrn^
number of occupants
Be careful to use the numbers for outdoor air, rather than total supply air. Total
supply air includes recirculated air as well as outdoor air.
3-21
-------
Evaluating and Correcting Radon Problems
ROOM
SCIENCE 301
CLASSROOMS 303, 305
CLASSROOMS 304, 306
MINIMUM
OUTDOOR
AIR (CFM)
400
250
200
NUMBER
OF
OCCUPANTS
25
25
22
MINIMUM
OUTDOOR AIR
(CFM/FERSON)
16
10
9
Figure 3-4: Outdoor Air Ventilation Rates in cfm/person
This chart is based on the example school illustrated in Figure 3-2. The outdoor air ventilation
rate in cfm/person should be compared to an applicable standard to see whether the space is adequately
ventilated. At minimum, a school should conform to the ventilation standards that applied when
it was constructed. Ideally, it should conform to ASHRAE Standard 62-1989, which calls for
15 cfm/person of outdoor air in classrooms, 20 cfm/person in laboratories (such as the science room).
The library has been omitted because it is an assembly area with a highly variable population.
These rooms were designed in 1970. At the time of construction, all of the rooms probably met the
ASHRAE recommended outdoor air ventilation rate (then 10 cfm/person in classrooms). Since 1970,
the room population and the ASHRAE standard have both changed, so that none of the rooms meet current
ASHRAE recommendations.
Note: Even though the total building outdoor air supply meets or exceeds ASHRAE
62-1989 (i.e., 15 dm of outdoor air per person in classrooms), poor air distribution
could cause areas of underventilation. Consider air flow patterns and any
complaints, such as stuffiness, as you evaluate ventilation.
3-22
-------
Evaluating and Correcting Radon Problems
Sample Working Floorplan 2
kitchen exhaust
hood
1975 original - slab on grade
1985 addition - over crawlspace
exh. fan (typical for
r^\ all toilets)
fan room
.
overnall
exh fan
Interlocked
with boiler
t, i unit vent (typ)
/fan 100cfmO.A.
unit vent (ty
2OO cfm O.A.
2O people
1O cfm/oerson
2O people
5 cfm/person
Note: "typ" means that
the unit ventilator in this
classroom is typical of the
other classrooms in this
area of the building.
AHU-1
on roof
unit vent (typ)
2OO cfm O.A.
25 people
8> cfm/person
unit vent (typ)
10O cfm O.A.
25 people
4 cfm/person
exh
hood
on kiln
AHU-2
on roof
This floorplan builds on Sample
Working Floorplan 1 by adding
information from the construction
plans and specifications. It shows
the HVAC zones, design outdoor
air ventilation rates in classrooms,
and rooms designed to operate
under negative pressure (rooms
where more air is exhausted than
is mechanically-supplied).
footing
(S~~\ shows area designed
to operate under
negative pressure
not tested
for radon
AHU = air handling unit
shows radon test results
below 4 pCi/L
shows radon test results
of4-10pCi/L
shows radon test
results over 1O pCi/L
unit vent = wall-mounted unit ventilator
3-23
-------
Evaluating and Correcting Radon Problems
c. Identify openings to the ground that may allow soil gas entry
The extent and location of openings to the ground may help to explain the
distribution of radon in the building and can affect the choice of an appropriate
mitigation strategy. Examine the architectural and mechanical plans for openings to
the ground that could be radon entry points and note these locations on your
working floorplan. Examples might include floor/wall joints; expansion joints;
utility tunnels; below-grade utility entries or sewer exits; pipe penetrations for
steam, hot water, or cooling water; open sump pits; and transitions between
different foundation types (such as crawlspaces or basements adjacent to areas built
slab-on-grade).
Sumps are often
radon entry points.
A sump can be
sealed to prevent
radon entry while
preserving its
intended function.
See Figure 4-1 on
page 4-6.
3-24
-------
Evaluating and Correcting Radon Problems
d. Identify foundation types and design (intended) subslab fill material
Information about the foundation type(s) and subslab fill material can be
obtained from the foundation plans. Identify the footing types and their location on
your working floorplan. The type and thickness of subslab fill material intended by
the building designer should also be indicated on the foundation plans. Check the
foundation type(s) and fill material in any additions, as well as in the original
building. Note this information on your working floor plans.
Sample Working Floorplan 3 builds on Sample Working Floorplan 2 (page 3-23)
by adding information about potential entry points shown on the mechanical plans.
3-25
-------
Evaluating and Correcting Radon Problems
Sample Working Floorplan 3
kitchen exhaust
hood
1975 original - slab on grade
footing (stem wall type)
floor drain
1985 addition - over crawispace
exh.fan (typical for
all toilets)
^y waste pipes through
floor (typ - all toilets)
fan room
over hall
exh fan
interlocked
with boiler ..
drain
trench
pipes tnrougn nodr
Library/
Media
'"008
unit vent (typ)
00 cfm O.A.
20 people
5 cfm/person
nk drain pipe
through floor
unit vent (typ)
200 cfm O.A.
20 people
10 cfm/person
sign subslab fill
material shown ae
4" coarse aggregate
crawispace - no slab
unit vent (typ)
20O cfm O.A.
25 people
& cfm/person
unit vent (typ)
10O cfm O.A.
25 people
4 cfm/person
sink drain
through
floor
This f loorplan builds on Sample
Working Hoorplan 2 by noting
where there are openings through the
slab. These openings are potential
radon entry points.
The new notes are printed in bold
lettering to make them more obvious.
\footing (stem
" wall type)
shows area designed
to operate under
negative pressure
poured
concrete
masonry
block
3-26
not tested
for radon
shows radon test results
below 4 pCi/L
shows radon test results
of4-10pCi/L
shows radon test
results over 10 pCi/L
-------
Evaluating and Correcting Radon Problems
2. Conduct a Walkthrough Inspection
No matter how complete and current your existing records may appear, an on-
site inspection of the school building is essential.
Tools for the walkthrough inspection include:
your working floorplan with notes showing radon test results and
information from building plans and specifications
flashlight
stiff wire, thin screwdriver, or ice pick for examining cracks and holes
protective clothing as needed (see discussion of worker protection in Section
10.2, pages 10-2 and 10-3).
heatless chemical smoke
whatever tools are needed for access to equipment, such as: ladder, wrenches,
screwdrivers, and nut drivers
Heatless chemical smoke is an essential tool for building investigations.
Chemical smoke reveals air circulation patterns without affecting those patterns
because it is the same temperature as the air. It is available in various dispensers,
commonly referred to as "smoke tubes," "smoke pencils," or "smoke guns." The
"smoke" is a mist of fine particles that is created when two chemicals combine. A
building investigator squeezes out a small amount of the "smoke," then observes
the direction and vigor of smoke movement. The smoke is extremely sensitive to
pressure differences. Building investigators, including radon mitigation contractors
who do diagnostic work, use chemical smoke regularly, and should be able to direct
you to a supplier. NOTE: The most common chemical smoke uses titanium
tetrachloride. Avoid inhaling the smoke, because it can irritate your respiratory
system.
The walkthrough should take place when the building is occupied or operating
as if occupied. To help understand your findings, make a record of weather
conditions, damper settings, fans that are or are not operating, and other pertinent
conditions while you are conducting the investigation. As you examine the HVAC
system, you may need to manipulate the controls in order to identify deficiencies
(such as outdoor air dampers that do not open).
Building investigators should remain alert to features of the building and
mechanical equipment that would indicate one type of radon control over another.
3-27
-------
Evaluating and Correcting Radon Problems
If the HVAC system was designed to supply 10 cfm of outdoor air/person (as
ASHRAE Standard 62 recommended from 1936 until 1973) and the system seems to
be in good working order, increasing outdoor air flows to dilute radon may not be
practical. If the subslab aggregate is crushed stone, an ASD system should be able to
develop a large negative pressure field below the slab.
a. Evaluate the condition of the ventilation system
This inspection is intended to identify gross problems with the HVAC system.
Detailed examination of the HVAC system condition and operation involves tools,
measurements, instrumentation and skills with which you may be unfamiliar, and
will be covered during the Detailed Investigation.
Look for signs of inadequate outdoor air or of ventilation malfunctions,
particularly in areas where occupants have complained about stuffiness or
discomfort. Indicate locations of problems on your working floorplan. Sample
Floorplan 4 on page 3-34 provides an example. Signs of ventilation problems
include the following:
blocked or obstructed outdoor air intakes
clogged filters
supply fans that are off when they should be operating
broken or malfunctioning controls, such as outdoor air dampers, thermostats,
or time clocks
fan motors with worn or loose belts
corroded fan housings that allow air leakage
missing ceiling tiles that open into air plenums
blocked or obstructed diffusers or grilles
freeze stats that have tripped and never been reset
fire dampers which have failed and are closed in ducts or plenums
3-28
-------
Evaluating and Correcting Radon Problems
You don't need the help of a
mechanical engineer to identify
problems like this. The exhaust fan
disconnect on the roof has been
switched "off," probably the last
time the fan was serviced. The
disconnect switch will override any
signals from the control system, and
the fan cannot operate until the
switch is set to "on" again.
It is common to find rooms in which air supplies have been blocked either
accidentally (e.g., by placing books, boxes, or papers on the outlets of unit
ventilators) or deliberately (e.g., by closing dampers or taping air outlets to eliminate
drafts). Chemical smoke can be used to confirm that dampers are open. Even
though a visual inspection suggests that a damper is open, other obstructions may
exist within the duct or within the intake grille itself. Check the supply diffusers,
return air grilles, and outdoor air intakes using the chemical smoke to verify air
flow.
3-29
-------
Evaluating and Correcting Radon Problems
Whatever the
control settings
may indicate,
little or no outdoor
air is being
supplied to this
area of the
building, because
the outdoor air
intake has been
blocked off. There
may be a history of
problems related to
the low outdoor air
ventilation rate
(for example,
complaints about
stuffiness).
Safety devices such as freeze stats and fire dampers sometimes cause problems by
cutting off the flow of outdoor ventilation air.
Freeze stats
Although most codes call for a minimum flow of outdoor air, regulations in some
parts of the country allow the control strategy to eliminate outdoor air flow
completely as a freeze protection measure. A freeze stat is a device (generally
located in the mixed air stream) that shuts off the associated fan or closes the
outdoor air damper when the temperature drops below a setpoint. Manual freeze
stats must be reset before the equipment will operate again. Inadequate outdoor air
ventilation can result if a freeze stat is not reset after it trips or if it is set to trip at a
high temperature.
3-30
-------
Evaluating and Correcting Radon Problems
Fire dampers
Fire dampers that are installed where ducts or ceiling plenums penetrate fire-rated
barriers can close (even when there has not been a fire) and obstruct air flow. The
mechanical floor plans should show fire damper locations. Gain access to these
dampers through access panels in the ductwork and check to confirm that the fire
dampers are in the open position.
This photograph shows the fan
controls of a typical classroom
unit ventilator. The controls
are readily accessible. If
teachers and students can
change fan operation at will,
they need to understand how
their actions affect radon
concentrations, as well as
overall indoor air quality.
Record the timing of occupied and unoccupied cycles. If outdoor air dampers are
open during the occupied cycle and closed during the unoccupied cycle, lengthening
the occupied cycle may reduce radon concentrations during occupied periods. Also
note how pieces of equipment such as unit ventilators and exhaust fans are
controlled. Exhaust fans that continue to operate during unoccupied periods may be
drawing in radon. On the other hand, teachers or other staff members may turn
"off" unit ventilators or fans that are noisy, distracting, or cause drafts.
3-31
-------
Evaluating and Correcting Radon Problems
If the control system uses time clocks,
make sure they read the correct
time. Radon and indoor air quality
problems can arise if time clock
settings slip due to power outages or
other factors.
^^^
"'" ''
Manipulate the
controls until they
call for the outdoor
air damper to open,
then observe the
actual damper
position. ITiis
outdoor air damper
is closed.
3-32
-------
Evaluating and Correcting Radon Problems
Check the condition of the filters at each piece of air handling equipment. Filters
should fit into their frames without gaps or cracks. Clogged filters can cause
underventilation by restricting air flow. Filters can overload until they sag or "blow
out" of their frames and allow unfiltered air to pass. This causes dirt to build up on
fans and coils, reducing the performance of mechanical equipment and shortening
its useful life. &
This photo shows a
common, low-
efficiency filter
that has "blown
out" due to the
excessive dirt that
collected as a
result of infrequent
filter changes.
Medium-efficiency
pleated filters
offer a longer
effective life and
remove smaller
particles from the
indoor air.
Medium-efficiency
filters should be
substituted for low-
efficiency filters
wherever possible.
Wherever your examination of the building plans indicated that a room or zone
should operate under negative pressure, use heatless chemical smoke to check air
flow patterns. Note: Air will be entering the room through some openings and
leaving through others. Focus on whether the room seems to be drawing in air
from outdoors, particularly through openings to the subslab or crawlspace. Check at
pipe penetrations, electrical outlets, the floor-wall joint, and other openings in the
floor or masonry walls. Mark the direction of air flow on your working floorplan
with notes and/or arrows as shown on Sample Working Floorplan 4.
3-33
-------
Evaluating and Correcting Radon Problems
kitchen exhaust
hood
Sample Working Floorplan 4
1975 original building - . 1985 addition -
over 6" coarse aggregate ; over (dirt-floored) crawlspace
VNv - footing exh. fan (typical for
D -/(stem ^ all toilets)
W f / wall type) W waste PjPe8 through
W ./ w-n vyp j Tf floor (typ _ a|| toj|ets)
fan room
over hall
'"OAIirtaka
In wall - not
blocked.
Flltara arซ
Interlocked
with boiler
drain
trench'
waste pipes
through
floor
AHU-1
on roof
exh
hood
on kiln1
sink drain
through
floor
AHU-2
on roof
exh. fan motor missing
AHJJ:4
Cafe:!
:007i*
pipe's "through floor
IClassrnU
035
Media p
-008JT
unit vent (typ
100 cfm O.A.
20 people
5 cfm/person
unit vent (typ)
200 cfm O.A.
20 people
10 cfm/person
O.A. dampers
are open -
typical
ounge _sink dra
emote enterin
through hole
unit vent filters are dirty.
| Some are almost totally clogged
I (both 1975 and 1985 sections)
typical for all
unit vents in
1975 building:
O.A. damper la
closed _^^,
unit vent (typ)
10O cfm O.A.
25 people
4 cfm/person
unit vent (typ)
200 cfm O.A.
25 people
8 cfm/person
OA, dampers
are open -
typical
Classrm^ } Classim*
022^1
5J3aif^~
Classrm ฃ
Q20/W,-
footing
(stem
wall type)
broken unit
vent fan
AHU-1 and AHU-2: filters are
dogged; O.A. Intakes dooed off
with plywood; leaky supply duct
art roof penetration (AHU-2)
This itoorplan builds on Sample Working
Hoorplan 3 by adding observations
from the walkthrough:
1) ventilation system problems
2) air flow patterns
The new notes are circled and printed in
bold lettering to make them more obvious.
shows area designed
to operate under
negative pressure
shows direction of
airflow using chemical smoke
(weather: cloudy, wind < 5 mph,
temperature around 20ฐ F)
poured concrete
masonry block
TIME CLOCK SCHEDULE:
occupied: 0900-1600
unoccupied: 1600-0900
not tested
for radon
shows radon test
results below 4 pCi/L
shows radon test
results of 4 -10 pCi/L
shows radon test
results over 10 pCi/L
3-34
-------
Evaluating and Correcting Radon Problems
b. Confirm soil gas entry at openings to the ground
This portion of the walkthrough investigation is intended to identify locations
that should be sealed to prevent radon entry. WARNING: Utility tunnels may
contain asbestos insulation, which should not be disturbed in any way during the
investigation.
Review the condition of potential radon entry points that were discovered
during the review of the building plans (page 3-24). Identify additional radon entry
points that were not shown in the plans, such as holes and cracks in the slab or the
foundation walls. Note your findings on your working floorplan. Although
sealing radon entry points is rarely sufficient to correct a radon problem, it always
improves the performance of other mitigation techniques. In some cases, it may be
necessary to seal large openings to the earth before any mitigation technique can be
successful. The size and locations of radon entry points can also affect the design of
ASD systems (e.g., fan sizing, placement of suction points).
Potential radon entry points include the following locations:
cracks at expansion joints and at the edges of slabs
utility pipe penetrations
utility tunnels containing heating pipes, conduit, and water pipes
subslab supply or return ducts or tunnels
dirt-floored crawlspaces
sumps
block walls
unsealed cold-pour slab joints and control saw-joints
large unsealed cracks caused by settling and/or slab shrinkage
3-35
-------
Evaluating and Correcting Radon Problems
This dry sump may
be an easy place to
examine the
subslab material
(such as fill and
native soil). It is
also likely to be a
radon entry point.
The investigator is
using chemical
smoke to see
whether air is
entering through
the perimeter
drain pipe.
To confirm whether a suspected radon entry point is actually allowing soil gas to
enter, probe cracks and holes with a stiff wire (such as a straightened coat hanger) to
see how far they extend. Release a small amount of heatless chemical smoke by a
suspected radon entry point and observe the direction and vigor of smoke
movement. If the smoke is drawn into the crack or blows back into the room, the
crack extends through the foundation into the underlying material. The direction
of smoke movement shows whether the area you are in is under positive or
negative pressure relative to the subslab area at the time of your inspection. If
smoke is drawn into the crack, the area is operating under positive pressure relative
to the subslab; if the smoke is blown away from the crack, the area is operating
under negative pressure relative to the subslab and radon may be entering.
NOTE: The air pressure below the slab can be different from the air pressure
outdoors (for example, on a windy day). The fact that a room is positive relative to
the outdoors does not mean that it will be positive relative to the subslab (which is
the source of radon gas).
3-36
-------
Evaluating and Correcting Radon Problems
Left: This photograph illustrates the
use of chemical smoke to evaluate
pressure differences. In this case, the
smoke is entering the room, indicating
that the room is under negative
pressure relative to the area below the
slab.
Right: The area around these plumbing pipes
should be checked with chemical smoke to see
whether it is a radon entry point.
3-37
-------
Evaluating and Correcting Radon Problems
Trim or interior
finish work often
covers the floor-
wall joint and
hides cracks that
allow radon to
enter. If the
smoke test shows
soil gas entry, this
floor-wall crack
may need to be
sealed during
mitigation.
3-38
-------
Ventilation System Restoration
4.0 Ventilation System Restoration
This section discusses restoration of the ventilation system. This is the next step
after performing the initial investigation. The restoration involves correcting the
ventilation deficiencies that were identified in the initial investigation and sealing
any large radon entry points.
By the end of the initial investigation, you should have collected the following
information:
areas where the radon concentration is above 4 pCi/L
locations of openings to the ground
locations of gross ventilation system deficiencies or malfunctions
rooms that run negative
It may be possible to correct your radon problems by closing large openings to the
ground and correcting the ventilation system problems you have identified. You
may need to obtain professional assistance for this corrective work. Radon
contractors who are listed by EPA's Radon Contractor Proficiency (RCP) program
have been trained in the proper selection and application of sealants. HVAC
engineers or mechanical contractors may be needed to design modifications, repair
or adjust the ventilation system.
4.1 Restore the Ventilation System
During the initial investigation, you developed one or more working floorplans
showing the locations of: 1) rooms with elevated radon concentrations, 2) rooms
supplied with less than 10 cfm/person of outdoor air, 3) rooms designed to run
negative, and 4) obvious ventilation problems such as broken equipment or
obstructed outdoor air intakes. Use this information to restore the ventilation
system, focusing on equipment that serves areas with elevated radon
concentrations.
a. Repair Ventilation System Deficiencies
If you have mechanically-supplied outdoor air ventilation, repair the
deficiencies you have identified so that, if possible, the ventilation system provides
at least as much outdoor air as was specified in the original design. Carrying out this
4-1
-------
Ventilation System Restoration
restoration throughout the entire school will help ensure that radon concentrations
remain low throughout the school, and will benefit indoor air quality in general.
Sometimes simple changes in the control of outdoor air intakes can significantly
increase the outdoor air ventilation rate. Examples include:
removing barriers that obstruct outdoor air intakes
increasing the minimum setting on outdoor air dampers
repairing defective unit ventilators and making sure that they operate (and
bring in outdoor air) whenever the school is occupied
Other deficiencies may be more complicated and expensive to repair. If the
school district does not have an HVAC engineer on staff, it may be necessary to seek
outside assistance to identify the cause of the ventilation system problems and the
most appropriate corrective actions.
If possible, increase the outdoor air ventilation to 15 cfm of outdoor air/person
in classrooms in accordance with ASHRAE Standard 62-1989. To avoid
depressurizing the building, mechanically supply additional outdoor air rather than
increasing exhaust quantities.
CAUTION: The capacity of your heating or cooling coils determines the amount of
outdoor air that can be conditioned, and may prohibit meeting ASHRAE 62-1989 on
a year-round basis. However, if the radon control strategy requires 15 cfm/person of
outdoor air ventilation, indoor radon levels will rise when outdoor air flows are
less than this amount.
m some areas of the country, freeze protection for coils may limit outdoor air
flows in winter. However, schools built according to pre-1973 ASHRAE
standards should have sufficient coil capacity to condition at least 10 cfm/person
of outdoor air ventilation.
Indoor moisture problems can develop in hot, humid climate zones if outdoor
air flows are increased beyond the capacity of cooling equipment to dehumidify
the air.
b. Modify Pressure Relationships
It may be difficult or impossible to prevent radon from entering rooms that
operate under negative pressure relative to the outdoors. Schools which rely on
natural ventilation or use exhaust fans to draw in outdoor air often run negative,
4-2
-------
Ventilation System Restoration
particularly if renovations have tightened the building, making it more difficult for
make-up (replacement) air to enter. It may be possible to counteract these negative
pressure influences by:
changing air distribution within the building so make-up air can flow where
it is needed - an engineer should approve any plan of this sort, to avoid
violating fire codes.
- undercut the bottoms of doors or install vaned openings in doors
- open transoms
supplying outdoor air to rooms that run negative
- install outdoor air dampers that open when local exhaust fans are running
- install unit ventilators or air handling units to introduce and condition
outdoor air
Schools that have mechanically-supplied outdoor ventilation air can also run
negative. If zones within your school run negative, even though you have
mechanically-supplied outdoor air ventilation and the outdoor air dampers appear
to open properly, your system may be out of balance. Air balancing by a certified test
and balance company can restore the ventilation system to proper adjustment,
reducing or eliminating the negative pressures that are drawing radon into the
building. See page 9-4 in Section 9 for guidance in obtaining quality test and balance
services. Also consider whether additional exhaust fans may have been installed,
increasing the powered exhaust cfm so that it outweighs the supply of make-up air.
c. Review Equipment Cycles
It may be possible to reduce the average radon concentration in your school by
manipulating the occupied and unoccupied cycles of your HVAC equipment.
(HVAC control cycles are discussed on pages 2-6,2-12,2-13,3-30 and 3-31,6-30 and 6-
31.) Schools commonly run more negative during the unoccupied cycle. If this is
the case for your building, initial improvements might include making certain that
exhaust fans are shut down during unoccupied periods and starting the occupied
cycle earlier in the day.
Sample Working Floorplan 5 on page 4-4 shows sealing requirements and
corrective actions for ventilation deficiencies in the example school.
4-3
-------
Ventilation System Restoration
Sample Working Hoorplari 5
1975 original - slab on grade 19S5 addition - over cravAspace
fan
room
over
hall
ซ""
Seal the
hole
around
the sink
drain
pipe.
Seal
open aump
AHU-4
Cafe.
007
II Kitchen
006
Replace
exh. fan
All unit vents in 1905 building:
Adjust to provide a minimum of
15 cfm/person O.A. if possible.
Stor.
005
;lassrm.
001
.Mech. Rm.
AHU-3
Library/
Media
008
/Off.
Class
Dlassrm.
033,
Classrm.
034
Classrm.
035
VIech. Rm.
009
)i(Locker
on
Gym
012
AHU-1
on roof
rAHU-2
on roof
Music
014
Lounge
130
Staff T
029
Stor.
026
025
All unit vents in
1975 building:
1. Re-open O.A.
dampers.
2. Adjust to
provide a
minimum of 15
cfm/person O.A.
1 if possible.
Clasfrm.
024
Classrm.
017
All unit vents in 1905 building:
Adjust to provide a minimum of
15 cfm/person O.A. if possible.
Uassrn
, 023
Classrii
022
I Classrm.
021
Classrm.
018
Classrm.
019
Classrm.
020
'AHU-I and AHU-2: Re-open the
O.A. intakes and replace the dirty
filters. AHU-2: Repair the leaks in
the supply duct.
Repair broken fan on unit vent.
Change time clock schedule to:
occupied: O7OO-16OO
unoccupied: 16OO-O7OO
-------
Ventilation System Restoration
4.2 Seal Large Radon Entry Points
Radon problems can rarely be corrected by sealing alone. Soil gas will enter a
building through any available openings to the ground whenever pressure
differentials create suction on the soil. Radon atoms are small enough to move
freely, even through small cracks in the slab or foundation walls that are not
obvious to the human eye. The time and expense involved in locating and sealing
all such openings is generally not justified.
On the other hand, sealing helps to support other radon mitigation strategies.
For example, ASD systems depend on the ability to develop a pressure field beneath
the slab. Large openings to the ground can restrict pressure field development. It is
worthwhile to seal large openings that are readily accessible.
Cracks and openings that can be closed permanently should be cleaned (to
improve adhesion) and sealed with polyurethane caulk. Note: Polyurethane caulk
gives off toxic fumes during installation. Installers should follow manufacturers'
directions and safety precautions wear appropriate protection and ventilate the
area.
This workman is grinding and
cleaning a floor-wall joint so it can be
sealed with polyurethane caulk.
Concrete dust and any other material
that might interfere with the
sealant's ability to stick must be
removed before the sealant is
applied.
4-5
-------
Ventilation System Restoration
Some openings to earth should be sealed with a removable material, so that they
are accessible in the future. Sump holes are an example of this type of opening.
Open sumps should be covered with an impermeable material such as plexiglass,
PVC sheets, treated 3/4" plywood, or sheet metal. The cover should be sealed
around the edges with silicone caulk. It may be necessary to replace the existing
sump pump with a submersible model and put a trapped floor drain in the newly
created sump cover.
Figure 4-1 shows one approach to sealing a sump hole. The sump cover is
equipped with a trap so that water from the floor surface can continue to drain into
the sump.
sump pump drain
seal with silicone caulk (this type
of caulk can be removed to allow
inspection/pump maintenance)
galvanized sheet steel cover
to seal to a shallow sump
water -trapped drain
sub-slab aggregate
interior drainage pipes
(existing)
compact sump pump
with sealed electrical
supply
Figure 4-1: Sealing a Sump Hole
Source: Camroden Associates
4-6
-------
Retest Radon Levels
5.0 Retest Radon Levels
After completing ventilation system restoration, it is time to decide whether to
carry out a Detailed Investigation or retest radon concentrations in the school to see
whether a Detailed Investigation is needed. This section provides guidance in
making this decision. If a decision is made to retest for radon, specific guidance is
provided as to how the measurements should be performed and how the retest
results should be interpreted.
If the pre-mitigation radon levels were greater than 10 pCi/L, you should proceed
to Section 6, Detailed Investigation and (in most cases) design and install an ASD
system. Where pre-mitigation radon levels were 10 pCi/L or lower and outdoor air
ventilation was blocked or severely restricted, it may be worthwhile to retest for
radon to determine whether restoration of the ventilation system (i.e., removing
obstructions, reconnecting damper operators) has increased outdoor air flows
enough to lower the radon concentration below 4 pCi/L. If actual air flow
measurements are available, the dilution equation presented in Figure 3-1 (and
discussed on page 3-7) can be used to determine whether retesting radon before the
Detailed Investigation is a practical option. Without air flow measurements, the
decision to retest must be made on the basis of common sense by considering' pre-
mitigation radon levels and the magnitude of the change in outdoor air ventilation
rates. NOTE: Even if the dilution equation shows that radon should be below 4
PCi/L, a radon retest must be performed to confirm that mitigation is surrpssfnl
In order to determine the effects of the ventilation system restoration relatively
quickly, EPA recommends making short-term radon measurements in areas where
pre-mitigation measurement results were above 4 pCi/L. Conduct two short-term
radon tests, either simultaneously or sequentially, and average the results. During
radon testing, use the quality assurance procedures discussed in Radon
Measurement in Schools - Revised Edition..
The radon test results will be affected by HVAC equipment cycling. Operate the
HVAC equipment on the occupied cycle 24 hours/day throughout the test period. If
the test is performed when the ventilation system is operating on normal
occupied/unoccupied cycling, test results are likely to be higher than occupants
actually encounter during occupied periods (i.e., radon levels usually rise during the
unoccupied cycle). Outdoor air dampers should not be allowed to open any further
than their minimum setting. This will simulate outdoor air ventilation during
extreme weather conditions. Measurement results obtained under these conditions
will reflect the radon concentrations when the ventilation system is operating at
minimum outdoor air ventilation rates.
5-1
-------
Retest Radon Levels
5.1 Evaluate Retest Results
Review the retest results, including quality assurance measurements. It is
common for some areas to require additional work while others are below 4 pCi/L.
Areas that show radon concentrations at or above 4 pCi/L during the retest
such as Classrooms 003, 004, and 033 on Sample Working Floorplan 6 - will
require further mitigation, probably including active soil depressurization.
Conduct a detailed investigation (see Section 6) to select the best mitigation
approach for areas that require additional treatment after the initial
improvements. If the radon level is less than 10 pCi/L, pressurization or
additional dilution are potential alternatives to ASD. Negative pressure
reduction could also be helpful. At higher radon concentrations, ASD alone or
in combination with dilution, pressurization, or reduction of negative pressures
will be needed.
Where the averaged results of the radon retest are below 4 pCi/L, you have
learned that the HVAC system can be used to control radon. Now you need to
adjust the system so that radon levels remain below 4 pCi/L whenever the
building is occupied. Figure 5-1 on page 5-3 shows how occupied/unoccupied
cycling affects radon concentrations in a typical school. Within each ventilation
zone, (room or rooms served by the same piece of ventilation equipment),
determine which room has the highest retest results. In that room, use a
continuous radon monitor (CRM) to collect continuous radon readings for a
minimum of 48 hours while the HVAC equipment cycles normally. Use the I
CRM results to determine the ventilation system start-up and shut-down times
necessary to maintain radon levels below 4 pCi/L whenever the building is
occupied. (NOTE: You may need professional assistance to obtain and interpret
continuous radon measurements.)
Example: Continuous radon readings in a classroom show that radon
concentrations start to fall at 7:30 am, when the ventilation system begins its
occupied cycle, but do not drop below 4 pd/L until 8:30 am. The students arrive
at 8:00 am. In this room, the occupied cycle should be adjusted to begin 1/2 hour
earlier (i.e., at 7:00 am) so that radon levels will be below 4 pd/L by 8:00 am.
If the retest shows radon at or below 4 pCi/L in the entire building after the
initial improvements: 1) use the procedure described above to adjust the
occupied/unoccupied cycle(s), and then 2) go to Section 9, Long Term Radon
Management. Long term radon management is critically important to prevent
5-2
-------
Retest Radon Levels
radon problems from recurring in the future. NOTE: Wherever the HVAC system
is used as part of the radon control strategy, radon concentrations can be expected to
vary with changes in the outdoor air ventilation rate (as illustrated in Figure 5-1).
Record and maintain outdoor air damper settings, the timing of occupied and
unoccupied cycles, and any other modifications that were made as part of the
HVAC-based mitigation strategy. Label the HVAC system to: 1) state that the HVAC
system is being used to control radon and 2) indicate the critical settings that must be
maintained. Avoid any change to key HVAC components that might cause radon
levels to rise.
U
CS
I
u
1
14-
12-
10-
8-
6-
4-
2-
weekend-
unoccupied
Monday night-
unoccupied
Outdoor air
-f- dampers
closed
Radon
Equip. Cycle
Tuesday-
occupied
CO
ง
s
V*
S
o
1
O
Outdoor air
dampers open
10
40
50
20 30
Time (hours)
Figure 5-1: Radon Levels and Control Cycles
The squared-off pattern shows the timing of occupied/unoccupied cycling. Radon levels
start to fall when the occupied cycle begins and outdoor air dampers open. When
outdoor air dampers close for the unoccupied cycle, radon levels rise.
NOTE: Your building may or may not behave in this manner.
5-3
-------
Retcst Radon Levels
Sample Working Floorplan 6
1975 original - slab on grade
1985 addition - over crawlspace
NEW
FILTERS
FORAHU-3
ANDAHU-4
Library/
Media
""obit
Classrm.
" 3)32
TIME
CLOCKS
ON NEW
SCHEDULE:
OCCUPIED
CYCLE
BEGINS
EARLIER
PIPE PENETRATION
SEALED WITH
POLYURETHANE
CAULK
Mech. |E
Rm. 009&
UNIT VENTS
- ALL O.A. DAMPERS RESTORED
TO PROPER OPERATION
- ALL FILTERS REPLACED
SUMP IS
SEALED
UNIT VENT O.A.
DAMPERS IN THE 1975
SECTION HAVE BEEN
ADJUSTED. ALL NOW
OPEN TO PROVIDE A
MINIMUM OF 1O
CFM/PERSON DURING
OCCUPIED PERIODS.
UNIT VENT FAN HAS
BEEN REPAIRED
Class rnr>
!022' "ป
Classrm ซ,
020 *S
Classrm,. f
"019'* <
O.A. INTAKES FOR AHU-1 AND AHU-
2 HAVE BEEN RE-OPENED;
FILTERS; LEAKS IN SUPPLY DUCT
ARE REPAIRED. OUTDOOR AIRFLOW j
IS NOW AT LEAST 1O CFM/PERSON j
URING OCCUPIED PERIODS.
ANDAHU^A
0; NEW I
LY DUCT /
R AIRFLOW/
I/PERSON/
'PS. ^X
I I not-tested
\ for radon
shows radon retest
results at 4 -1O pCi/L
I ~"~] shows radon retest jgjjjjliil shows radon retest
I I results below 4 pCi/L iBlii results above 1O pCi/L
Notes indicate sealing, restoration of HVAC system
poured
concrete
masonry
block
Restora tion of the HVAC system appears to have reduced radon below 4 p Ci/ L in most of the rooms
that were originally between 4 and 10 p Ci/ L. The school should institute a program of preventive
maintenance and annual retesting to ensure that radon levels in those areas remain below 4 pCi/L.
Meanwhile, radon remains at or above 10 pCi/L in the three classrooms that were originally over 10
pCi/L A detailed investigation will be required to design a successful approach to mitigation in those
three classrooms using active soil depressurization (ASD). The Art and Music classrooms also remain
above 4pCi/Land will require a detailed investigation.
_
-------
Detailed Investigation
6.0 Detailed Investigation
This section provides guidance in performing the detailed investigation.
Mitigation strategies are discussed in detail to help you understand how the
elements of the investigation will affect the selection of a strategy. Basic
information is provided on how typical radon diagnostics are performed during the
investigation to determine the viability of each mitigation strategy. The team
requirements are also discussed, to help select additional qualified team members.
A detailed building investigation is needed under any of the following
circumstances:
pre-mitigation indoor radon levels are higher than 10 pCi/L in some areas of
the building
an initial building investigation did not find obvious ventilation problems
initial ventilation system restoration was not successful at reducing radon
below 4 pCi/L
As with the initial inspection, architectural and mechanical plans and
specifications (where available) supplement the information available from direct
inspection of the building. Investigators should have specific knowledge of radon
control methods, foundation construction practice, radon diagnostic tests, and
HVAC equipment and controls.
6.1 The Detailed Investigation Team
A team approach to the investigation is suggested to promote full consideration
of potential mitigation strategies. The team should include representation in three
critical areas of knowledge:
1) Someone familiar with the building, the occupancy schedule, and the HVAC
equipment. This will probably be a school staff person.
2) Someone who has successfully participated in the EPA's Radon Contractor
Proficiency Program (RCP) or is a state-certified radon mitigation contractor
should be used for the foundation investigation. Experienced radon contractors
should be able to provide specialized equipment for radon diagnostics, such as
radon sniffers, chemical smoke, pressure gauges, and slab drilling equipment.
6-1
-------
Detailed Investigation
Information on specific radon measurement firms and mitigation contractors in
your area can be obtained from your state radon office (see Appendix B).
3) A school facility person, mechanical contractor, and/or a mechanical engineer
who knows the applicable codes and is able to evaluate the ventilation system.
This could be an engineer from an HVAC company under contract to perform
school HVAC maintenance, design, and/or renovation work.
It is critically important to use experienced, trained people when evaluating,
repairing, designing and installing air handling equipment. Registered mechanical
engineers are traditionally used to evaluate, design and oversee repairs and new
installations of ventilation equipment.
Potential Team Members and What They Can Contribute to the Detailed Investigation.
School administration representative - can serve as liaison with school superintendent's office,
board of education, and other district decisionmakers; could also be liaison with media-
Facility manager - familiar with school mechanical system design, operation, and '
maintenance; can provide access to equipment and change controls if necessary during the >
investigation ', 1 -
Teacher/staff representative - liaison with other staff members; can help build support for -
mitigation effort ,
PTA representative - liaison with other parents; can help to build support for mitigation effort
RCP contractor - familiar with radon diagnostics and mitigation, can interpret radon > . ;
measurement results, can conduct and interpret subslab vacuum test ' '." ',-,'-,
Mechanical contractor - familiar with HVAC installation and modification - .
Mechanical engineer - familiar with HVAC systems, can conduct and interpret ventilation"
assessment --' -,'-'
Indoor air quality consultants - can identify, assess, develop mitigation plans and interpret
ventilation assessment for radon and other potential IAQ problems, ' "
6.2 Radon Mitigation Techniques
The goal of the Detailed Building Investigation is to identify one or more radon
mitigation strategies that are likely to be successful in your building. As discussed in
Section 2, radon mitigation systems can function by preventing radon from entering
the building, diluting indoor radon concentrations, or a combination of these
approaches. This section provides an overview to familiarize you with current
radon mitigation techniques.
6-2
-------
Detailed Investigation
Mitigation approaches that change pressure relationships to prevent soil gas
from entering the building can be successful regardless of the radon concentration.
Soil gas cannot enter when the air pressure indoors is higher than the air pressure
under the occupied space, a goal that can be achieved by lowering the air pressure in
the soil or by raising the air pressure inside the building. ASD and pressurization
both prevent radon entry by controlling pressure differences.
Sealing cracks and openings to the ground helps to prevent radon entry. Because
sealing is rarely successful as a stand-alone approach to mitigation, it will not be
discussed in detail in this section. However, sealing may be necessary to ensure the
success of other mitigation strategies. Sealing of above-grade openings such as leaky
windows or unweatherstripped doors can be important to the success of mitigation
based on pressurization. Section 4, pages 4-5 and 4-6 provides more information on
sealing techniques.
Dilution is most appropriate for treating radon levels of 10 pCi/L or below.
Section 3.4 discussed an approach to mitigating low radon levels by repairing or
adjusting the ventilation system to increase the flow of outdoor air into the
building. Section 6.2.c describes a more detailed technical evaluation of dilution as a
mitigation approach.
a. Active soil depressurization
Active soil depressurization (ASD) systems use ductwork and fans to lower the
air pressure in the soil below the building slab (or through an installed membrane
barrier, if there is no slab). The system develops and maintains a negative pressure
field by withdrawing soil gas through one or more suction points, holes through the
slab or membrane. When the system functions properly, air is sucked out of the
building through any foundation cracks, so that radon cannot enter. The soil gas
withdrawn by the ASD fans is ducted out of the building and exhausted above (and
away from) the highest air intake or building opening so that it will not be drawn
back indoors.
Subslab conditions are critical to the success of this mitigation approach. If the
soils are fine-grained, wet, or tightly-compacted, the negative pressure field will only
extend for a short distance, and multiple suction points will be necessary. In a
typical ASD installation, fill material and/or soil is removed below each suction
point to increase pressure field extension. If air moves too easily through the soil or
there are holes in the foundation, the fan could suck air without developing an
adequate negative pressure field. ASD fans are designed to operate at high static
pressures and low air flows.
6-3
-------
Detailed Investigation
ASD systems have been effectively used in buildings with slab on grade,
basement and crawlspace foundations. The complexity of designing and installing
these systems varies depending on the foundation details (as well as other building
features, such as fire walls). It is recommended that the system be designed and
installed with the aid of a radon contractor who is listed in the EPA Radon
Contractor Proficiency (RCP) program or is state-certified.
ASD under slabs
The following diagnostic procedures are used to evaluate the potential for ASD
under a slab:
review of architectural and mechanical plans and construction specifications
* visual inspection to examine the foundation and subslab material
vacuum test (Figure 6-1 illustrates how ASD systems can be adapted to deal
with subslab obstacles)
ASD under a membrane
Crawlspaces usually do not have concrete floor slabs. A plastic membrane can be
rolled out (as shown in Figure 6-2) and suction can be applied beneath the
membrane to depressurize the soil. The pressure field can be extended by creating a
grid of perforated pipe or other drainage material under the membrane. No
diagnostic procedures are needed to evaluate a building's suitability for this
mitigation technique; proper fan selection and quality control during installation
are the keys to success. Use of the crawlspace area for storage will be limited. To
avoid puncturing or other damage, walking on the membrane should be restricted
to emergency access to utility lines, unless it is both underlain and covered with
sand.
6-4
-------
Detailed Investigation
Exhaust above roof. Locate outlet
away from air intakes. Fan should
be rated for exterior use.
Treatment at penetrations should meet fire codes.
Duct should meet applicable
fire and safety codes
sฃs;-l
-------
Detailed Investigation
Other applications of active soil depressurization
Sometimes it is possible to control radon levels by withdrawing air from a
crawlspace, utility tunnel, or subslab ventilation duct, rather than creating suction
under a slab or membrane. These alternatives to ASD require careful study. For
example, pipes routed through utility tunnels may be covered with asbestos
insulation that could be disturbed by the operation of the mitigation fan.
b. Pressurizing the occupied space
Pressurization systems use fans to blow conditioned (filtered, then heated or
cooled) outdoor air into the building, so that the indoor air pressure is higher than
the air pressure in the soil. A building can be thought of as a large box with a
number of air leaks between the inside and the outside. The larger the total leakage
area, the more outdoor air will be needed to pressurize the building. Mitigation
using pressurization may involve tightening the building shell to reduce the
leakage area. NOTE: Providing outdoor air to meet current ventilation standards
does not necessarily mean that a space will be pressurized. Pressurization occurs
when the quantity of air that is mechanically supplied to a space is greater than the
quantity of air that is mechanically removed.
The following diagnostic procedures are used to evaluate the potential for
pressurization:
review of architectural and mechanical plans and construction specifications
* inspection of building structure
* fan door test (see page 6-26)
A fan door test is conducted by placing a calibrated fan in a door opening and recording the indoor-
outdoor air pressure differences created when the fan operates at different speeds (Le., different
air flows). The pressure differences and air flows generated during the test are used to calculate
the leakage area of the building. '',''
6-6
-------
Detailed Investigation
c. Dilution
Increasing the amount of outdoor air entering the building reduces radon
concentrations by dilution. This strategy can be accomplished either by increasing
the exhaust rate or by blowing additional outdoor air into the building. If the
change in outdoor air flows could occur without affecting pressure differentials, the
effect on indoor radon concentrations could be predicted simply by applying this
equation:
Final radon level = Pre-mitigation radon level x Initial outdoor air flow
Final outdoor air flow
For example, doubling the outdoor air ventilation rate would cut radon
concentrations in half, tripling the outdoor air ventilation rate would lower radon
to 1/3 of the pre-mitigation level, and so on. The dilution equation should be
applied to air flow quantities that are measured with the outdoor air damper(s) at
the minimum "occupied" setting. In many cases, the same weather conditions that
cause outdoor air dampers to close to the minimum setting also cause maximum
radon entry (e.g., cold outdoor temperatures).
Changes in outdoor air flows often do change air pressure relationships, with
results that may either support or hinder your radon control efforts. Blowing in
additional outdoor ventilation air is the preferred way to lower radon
concentrations by dilution, because it tends to pressurize the building (or at least
reduce negative pressures). Increasing the exhaust rate is a less effective approach to
dilution, because it tends to depressurize the building and may actually increase
radon entry.
The following diagnostic procedures are used to evaluate the potential for
dilution:
review of architectural and mechanical plans and construction specifications
inspection of building mechanical systems
calculation or direct measurement of outdoor air ventilation rates
- direct measurement of flow rates
- carbon dioxide measurements
- calculation of outdoor air ventilation rates using temperature
measurements (known as "thermal mass balance")
6-7
-------
Detailed Investigation
6.3 Elements of the Detailed Investigation
Figure 6-3 summarizes the relationship between the three mitigation strategies and
the elements of the detailed building investigation. The detailed investigation
builds on what was learned during the initial investigation, but may also involve a
number of diagnostic tests, shown in italics in Figure 6-3. These tests collect
information that is either useful or necessary in selecting and designing a mitigation
system.
Figure 6-3: Elements of the Detailed Investigation
FOUNDATION INVESTIGATION
Review foundation plans/specs
Visual inspection
Subslab radon test
Subslab vacuum test
BUILDING SHELL INVESTIGATION
Review building plans/specs
Visual inspection
Fan pressurization test
VENTILATION INVESTIGATION
Review HVAC plans/specs
- ventilation control strategy
- air pressure relationships
- equipment capacity
Visual inspection
Ventilation evaluation
Pressure differentials
ASD
X
X
X
X
X
X
X
X
X
Pressurization
X
X
X
X
X
X
X
X
X
X
Dilution
X
X
X
X
X
X
As suggested in Section 3, it is helpful to take notes on a working floorplan, a
small floorplan of the building. Recording information on a floorplan will help you
to understand the spatial relationships involved in radon distribution, air flow
patterns, and the use of ventilation equipment in your building.
6-8
-------
Detailed Investigation
DETAILED INVESTIGATION
I. Review the radon test results
2.
Review the plans, construction specifications and other documentation
a. Identify factors that affect active soil depressurization
b. Identify factors that affect pressurization
d. Identify factors that affect dilution
3. Conduct a building inspection and diagnostic testing
a. Foundation inspection and diagnostic testing
b. Building shell inspection and diagnostic testing
c. Ventilation inspection and diagnostic testing
1. Review the radon test results
I
Review all radon test results for the areas of interest and consider whether there
seem to be any patterns in the distribution of radon. If radon concentrations are
relatively similar within an area that has a common air distribution system, the air
distribution system might be the radon source. Scattered locations with high radon
concentrations may be locations of entry points. Sample Working Floorplan 7 shows
the radon test history for the example school shown in Sample Working Floorplans
1 through 6.
6-9
-------
Detailed Investigation
6.0 pCi/L
Sample Working Floorplan 7
.Cafe.II,,
1975 original - slab on grade 1985 addition - over crawlspace
105 pCI/L% 125 pCi/L |
Kitchen
Mech. Rm.
iMech. Rm.|
009 I
ie.
015
lassrmflj , Classrm *v ^ 211 ^ Classrm.ฃ
mmmmiim 002$^' '/v< 001^( .
Classrrn.Bil ..Classrm, %
^
Staff T.
029
JClassJ
1028 jf
pass!
^""
otor.
026
T
025
1
I
Room
No.
OO3
004
O33
Art
Music
fclassnn^
024^^^_
Pre-mitigation
(pCi/L)
15.0
13.0
135
9.6
9.7
I
I
I
I
"Class rm'^
023!'^
After ventilation
restoration
(pCi/U
125
105
11.0
6.0
6.O
Classnn^ Cbssrmf^'
O22'tj f 021 f4?$''
Classrm^l
' '
Classrrn *
Classrm
not tested
for radon
shows radon retest results
below 4 pCi/L
i shows radon retest results
| at 4 - 1O pCi/L
I shows radon retest results
\ over 10 pCi/L
This floorplan shows the radon test history for the example school shown
in Sample Working Floorplans 1 through 6. Note that radon test results in
the Art and Music areas are very similar. Because these rooms share a
common air handling unit (AHU-2), investigators should consider the
possibility that the air distribution system is affecting radon distribution.
6-10
-------
Detailed Investigation
2. Review the plans, construction specifications, and other documentation
The Detailed Investigation team should make use of the information during the
Initial Investigation, such as the inventory of HVAC equipment and the working
floorplans (and other records) showing HVAC zones, areas that operate under
negative pressure by design, design outdoor air ventilation rates, and observations of
the ventilation system and potential radon entry points. (Records of ventilation
system restoration work and sealing work should also be included, along with the
results of any radon retesting.) If no Initial Investigation was conducted, review
pages 3-14 through 3-38 and collect this data during the Detailed Investigation.
Obtain and examine available architectural and mechanical plans, specifications,
and other construction documents for all rooms with elevated radon concentrations.
Consider the original building and any addition as if each were a separate building.
a. Identify factors that affect active soil depressurization
To be successful, an active soil depressurization (ASD) system must establish and
maintain a negative pressure field in the soil beneath the building. Throughout the
Detailed Investigation, attempt to identify features that would promote or impede
the installation and operation of an ASD system. Figure 6-4 and the accompanying
discussion expand on the flowchart shown in Figure 3-1 (page 3-3) and present a
process for evaluating ASD-based mitigation.
6-11
-------
Detailed Investigation
Evaluate potential
forASD-based
mitigation strategy
Is the
building
depressurized by
more than 5
pascals?
Does
vacuum test
how good pressure
field
extension
Are
air handlers
mining soil
air?
Air leaks
to subslab?
Treat locations
where air handlers
mine soil air
Treat excessive
Consider
ASD
alone or in
combination
Figure 6-4: Flowchart for Evaluating ASD-based Mitigation
Does
vacuum test
show good
pressure field
extension,
An experienced radon mitigation contractor (EPA-listed or state-
certified) will be able to conduct the vacuum test and interpret
the results. Good pressure field extension under the slab
indicates that ASD is likely to be successful. If it is too difficult to
withdraw air from beneath the slab, a large number of suction
points may be needed, increasing the cost of ASD. If it is too easy
to withdraw air from beneath the slab, foundation leaks may be
present that could defeat pressure field extension.
The vacuum test cannot be conducted in areas without slabs (e.g.,
dirt-floored crawlspaces). However, where a membrane can be
installed on the floor, sub-membrane depressurization is a
mitigation technique that operates on the same principle as ASD.
(See page 6-4 and Figure 6-2 on page 6-5.)
6-12
-------
Detailed Investigation
'Is the
building
depressurized by
more than 5
pascals?
If tests with chemical smoke or measurements of pressure
differences indicate that soil gas is entering through cracks or
holes in the slab, sealing (eliminating easily-accessible radon
pathways) may be important to the success of your radon
mitigation efforts. This is particularly true if ASD is being used
and vacuum test results indicate poor pressure field extension.
If pressure differential measurements indicate that the building
appears to operate at 5 or more
pascals (0.02" water column p^^
[W.C.]) negative relative to the
outdoors and the vacuum test
did not show good pressure
field extension, negative
Agaseal is almit of aiE.pressui-e
equal to CXOQ4" water coruam
Are
air handlers
mining soil
air?
pressures in the building might
interfere with the success of an ASD system. Consider adjusting
the HVAC system to increase the outdoor air flow into the
building, reducing the amount of powered exhaust (but
maintaining the exhaust quantities necessary to remove airborne
contaminants), or adding air handling equipment to supply
more conditioned outdoor air. Ideally, the total volume of
mechanically-supplied outdoor air should equal or exceed the
total powered exhaust.
In some buildings, the ventilation system functions to
unintentionally draw soil air indoors. Look for the following:
return ductwork below the slab
return ductwork in a crawlspace
a mechanical room that functions as the return air plenum
for an air handler
a masonry wall (i.e., hollow block cores) that ends in a return
air plenum
a return plenum built tight against the slab, so that openings
such as pipe penetrations, cracks in the slab, and/or the floor-
wall crack are under negative pressure
If air handlers are mining soil air, it is important to seal the
pathway that allows soil air to enter the building. Sub-slab
ductwork is very difficult to seal, and may have to be abandoned
and re-routed above the slab.
6-13
-------
Detailed Investigation
Architectural and mechanical plans reveal pathways for air movement that may
affect radon distribution within the building. Some pathways are obvious, such as
air distribution ducts, corridors, and stairways. Less obvious pathways include
plumbing chases, interior subslab walls and footings, crawlspaces and utility tunnels.
You may need to block pathways or modify pressure relationships within them in
order to correct the radon problem in some areas. Vertical pathways are of particular
interest if there is elevated radon in the upper levels of a multi-story building.
Review the architectural and mechanical plans and specifications (if available) for
a description of the substructure construction in each area, whether there is fill
beneath the slab, and a description of the type of fill. The number and type of fans
and the number of suction points required for a successful ASD system will depend
on: 1) the number and location of subslab barriers (such as subslab walls on footings),
2) the ease of air movement through the material under the slab, and 3) cracks and
holes (in the slab and foundation walls) that connect the subslab soil to the indoor
and outdoor air. Ideal conditions for ASD would include: low-permeability native
soil covered by a layer of clean, coarse, permeable fill or drainage material under the
slab, no holes or significant cracks in the foundation, and no subslab barriers.
Foundation type
The type of foundation affects the selection and design of a mitigation method.
Most schools are slab on grade construction, while fewer have crawlspaces and
basements. An ASD system can only develop a negative pressure field in the soil if
there is a barrier between the soil and the building interior. Crawlspaces without
slabs would require installation of a slab or membrane in order to use ASD.
The same building may combine two or more foundation types. Transitions
between foundation types (or between the original building and later additions) are
likely to have obstacles to pressure field extension below the slab, such as footings. If
there are many obstacles below the slab, an ASD system design could require a large
number of suction points, adding to the cost and difficulty of installation.
Subslab material
Construction plans and specifications describe the materials that should be under
the building slab. Dry fine sand, silt, or clay are tight soils that inhibit soil gas
movement. Active soil depressurization will be more effective and less expensive to
install if there is a coarse aggregate (such as coarse, crushed stone or coarse, clean
gravel) under the slab.
If the foundation is relatively airtight and there is porous, crushed aggregate
under the slab, one small fan with a small number of suction points may be all that
6-14
-------
Detailed Investigation
is needed. In one research school, a negative pressure field was extended through
3/4 inch diameter aggregate under 50,000 square feet of slab with a single suction
point. At the other extreme, a building with compacted sand under the slab and
many subslab walls required 14 suction points for the same floor area.
Barriers and/or large air leaks
Foundation plans show slab joints, interior subslab walls on footings, and
transitions between different foundation types that can obstruct the development of
an ASD pressure field below the slab.
Utility tunnels beneath the slab can be pathways for radon movement into
buildings. They are usually obstacles to a standard ASD system, but it is sometimes
possible to depressurize utility tunnels as a variation on ASD. WARNING: Utility
tunnels sometimes contain asbestos, even after it has been removed from other
locations. The district's asbestos officer should be consulted before creating air
movement in tunnels that contain asbestos-containing material.
Ventilation systems that "mine" radon
Sometimes a trench below the slab forms the return air duct for an air handling
system. This is not simply a radon entry point; it is the equivalent of mining soil gas
for distribution to the building and must be contended with in any mitigation plan.
If the building has ductwork below the slab or in a crawlspace, note the
location(s) on your working floorplan. Supply or return air ducts located in
crawlspaces or under the slab can mine radon and distribute it in a building. Subslab
supply ducts are under positive pressure when the air handler is running, but leaks
in the ducts may draw in soil gas when fans are off. Return ducts in crawlspaces or
under the slab are under negative pressure and will draw in soil gas through leaks,
whether or not the return fan is operating. Wherever the return duct leaks, it will
lower air pressure under the slab. This competes with the ASD system, which is
trying to accomplish the same thing. Appropriate diagnostics can determine what
effect subslab return ducts will have on an ASD system. Abandoned ductwork can
sometimes be used as part of an ASD system.
Ventilation systems can also mine soil gas in ways that are more difficult to
discover than subslab ductwork. Either of the following features might be found as a
detail on the construction plans, although they are more likely to be discovered
during the walkthrough inspection:
(1) An air handler may be installed so the return air side depressurizes a mechanical
room (or a smaller area, such as portions of the floor slab and wall that are within
6-15
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Detailed Investigation
the return air cabinet). If there is an opening to the ground within the return air
plenum, the unit will draw soil gas into the building.
(2) In an area with an above-ceiling return air plenum, a masonry wall that
penetrates the floor slab has open block tops. The return air plenum operates
under negative pressure, pulling soil gas up through the block cores and back to
the air handling unit, which blows soil gas into the building.
Features that should be avoided during the vacuum test
As you review the building plans, look for potential hazards that may be
encountered while drilling holes in the slab, such as radiant hydronic heating pipes
in the slab or electrical conduit or water pipes under the slab. Note the locations of
these features on your working floorplan, and avoid them when you drill holes for
the vacuum test.
6-16
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Detailed Investigation
Sample Working Floorplan 8
1975 original-slab ongrade (1985 addjtion . ovef craw|space
X
poured
concrete
bearing
wall
I75cfm\
urn V-
(typ for &
masonry
wall on
footing
25Ocfm
supply
(typ for S)
oured concrete
bearing wall (typ) \
Classrm. 032 . .* .
FILL: boundary**
4" CRUSHED STONE between 1975
and 1985
sections
not tested
for radon
return
plenum
(no
return
ducte)
I - ,'j shown radon retest
I...1'.'-..'* 1 results below 4 pCi/L
1 shows radon retest
results of 4-10 pCi/L
shows radon retest
results over 1O pCi/L
poured
concrete
masonry
block
sanitary
waste piping
This floorplan shows part of the mechanical fioorplan for the Art and Music area and
the foundation plan for the classroom area. Note that:
1. The substructure of the classroom area is slab on grade over crushed stone. This is
likely to promote development of a negative pressure field - a good sign for ASD
Investigators should avoid the waste piping when drilling for the subslab vacuum test
2. The area above the ceiling of the Art and Music areas is a return plenum that extends
across a masonry wall. Negative pressure in the return air plenum could be pulling
radon up through the block cores.
6-17
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Detailed Investigation
b. Identify factors that affect pressurization
Check the architectural plans for
information about the footing design
used in your building. Interior footings
affect ASD system design because
they are obstacles to pressure field
extension. The design shown to the
left, with a block wall extending
below the slab, poses additional
problems because radon can enter the
building through the block cores. If
there is a return plenum at the top of
the wall, negative pressure in the
plenum is likely to draw radon up
through the block cores. Once in the
plenum, the radon mixes with the
return airstream and is distributed
back into the occupied space.
Four basic types of outdoor air ventilation systems are typically found in schools.
The type of ventilation system found in a building affects its suitability for
pressurization. If different areas of the same building have different ventilation
systems, some areas may run negative by design, while other areas may be designed
to operate at neutral or positive pressure.
Read the following discussion of ventilation system designs and compare them
to your mechanical plans and specifications. If your existing ventilation system
6-18
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Detailed Investigation
would not support pressurization and you are not planning renovations in the near
future, pressurization is probably not a practical mitigation option.
Buildings with no mechanical ventilation: Buildings that rely entirely on
natural ventilation, with no supply or exhaust fans, tend to run negative relative
to the subslab soil. For radon mitigation based on pressurization, a mechanical
ventilation system would have to be installed to supply and distribute
conditioned air. The amount of outdoor air ventilation required would depend
on the tightness of the building, but should be sufficient to provide adequate
conditioned outdoor air (preferably 15 cfm/person, but at least 10 cfm/person)
without opening windows. Pressurization systems can easily be defeated by open
windows or propped-open exterior doors.
Buildings with fan powered outdoor ventilation air but no exhaust: If a building
has fan powered outdoor ventilation air with no mechanical exhaust, the HVAC
system was probably designed to pressurize the building. This is an ideal starting
point for mitigation by pressurization. You will need to know the amount of
outdoor air being blown into the building when it is in the occupied mode, the
capacity of heating and cooling coils, and the tightness of the building shell. If the
building is too leaky, tightening it will help to control radon and save fuel costs
by reducing the infiltration of outdoor air during unoccupied periods, when the
HVAC system is not pressurizing the building.
Buildings with exhaust but no fan powered outdoor air ventilation: If a building
has exhaust fans (or passive roof vents) but no mechanically-supplied outdoor air
ventilation, the HVAC system tends to depressurize the building. To mitigate
radon using pressurization, a greater amount of outdoor air must be blown into
the building than is being exhausted. In this situation, a ventilation system that
supplies conditioned outdoor air to the building must be designed and installed,
because there is no existing equipment available to use. The amount of outdoor
air needed depends on the amount of air exhausted and the tightness of the
building.
Buildings with exhaust and outdoor air ventilation: Some buildings have both
outdoor air intake fans and exhaust fans. If the volume of powered exhaust is
greater than the volume of outdoor air introduced by the mechanical system,
then the building is depressurized by the difference in air flows. (See Section
3.4.1.b., page 3-19.) It may be possible to use the existing equipment to pressurize
the building, either by reducing exhaust or by increasing outdoor air flow and
tightening the building.
6-19
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Detailed Investigation
c. Identify factors that affect dilution
If you conducted an Initial Investigation, you may already have all of the
information described below. If not, review your plans, specifications, and the most
recent test and balance report (if available), and see pages 3-16 to 3-26 for guidance.
The goal of the review is to achieve the following:
create an inventory of air handling equipment within the building
- list all supply, return and exhaust fans and their locations
- record any air flows shown on the equipment schedule (or, if available,
from more recent measurements by test and balance or controls
contractors). For supply fans with outdoor air intakes, note minimum and
maximum outdoor cfm as well as total supply air cfm.
review control setpoints and logic for all air handling equipment
- for each air handling unit, note the outdoor air damper control sequences,
including mixed air setting and freezestat setting
- review occupied and unoccupied cycles for damper settings and fan
operation
- note exhaust fan controls (which fans are controlled by time clocks, which
by local switching, and which - if any ~ run continuously)
review the HVAC system design and mark the working floorplan
- show any areas that rely on operable windows for outdoor air ventilation
- show the areas served by each item of air handling equipment
2. Conduct a building inspection and diagnostic testing
A walkthrough building inspection by school personnel, the radon contractor,
and a mechanical engineer is an important part of the detailed investigation. The
inspection can include evaluation of the subslab area, building shell, and/or HVAC
system, depending on the type(s) of mitigation under consideration.
The walkthrough provides an opportunity for the members of the team to share
views on the important features of the building. It is critical for a school person who
6-20
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Detailed Investigation
is familiar with the building and the HVAC equipment to be part of this effort.
Mitigation based on pressurization or dilution can only be successful if facility staff,
including staff members who may be responsible for energy conservation programs,
understand how the mitigation system functions.
Before beginning the walkthrough inspection, review pages 3-27 through 3-38 for
a description of the tools you will require and the types of information to collect.
You will also need a drill (and bit) to open a hole in the slab, preferably a I 1/4"
masonry core drill. A 1 1/4" drill bit is the right size to drill holes for the vacuum
suction test.
Building investigators may use any or all of the following tests as they evaluate
mitigation alternatives:
subslab radon test
vacuum test of pressure field extension
pressure differential measurements
ventilation evaluation
fan door test
a. Foundation inspection and diagnostic testing
The foundation inspection should follow (and build upon) information collected
during the review of construction documents. It consists of an examination of the
subslab aggregate and radon entry points. In addition, several diagnostic tests -
subslab radon test, the vacuum test of pressure field extension, and pressure
differential measurements - are generally conducted during the foundation
investigation. While inspecting the substructure, consider locations where holes can
be drilled through the slab, used for the vacuum test, and then unobtrusively
repaired.
Use heatless chemical smoke to check for air movement at suspected radon entry
points, and note whether the smoke is entering or leaving the building. Potential
entry points are listed on page 3-35, and should have been recorded on your working
floorplan if you conducted an Initial Investigation.
6-21
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Detailed Investigation
If there is no way to observe the subslab material through existing openings, drill
a hole (preferably in an inconspicuous location such as a supply closet) to see
whether your building plans and specifications describe the actual conditions.
Warnings:
1. Holes drilled through floor tiles that contain asbestos must be made by
appropriate personnel, taking required precautions.
2. When you are considering where to put the hole, do not drill through the slab
over pipes, electrical conduit, ducts, or footings.
Drill a hole through the slab at a location that avoids hitting any footings or
thickened slab areas as shown on the plans. Remove the concrete dust and debris
from the hole and examine the subslab material. If possible, take a sample so that
you can handle it. Refill the hole with polyurethane caulk when you have finished
examining the subslab aggregate and conducting diagnostic testing.
Subslab treatments reflect the requirements of the specific site and the materials
that are locally available. In different regions of the country, you might find coarse
gravel or crushed stone, compacted sand, native earth, or other materials beneath
the slab. Note your observations. Is the material coarse or fine? Wet or dry?
Crushed rock or rounded naturally-occurring stone? Native or imported fill? Is it
consistent with the information in the plans and specifications? Record your
answers on the working floorplan. You should examine sub-slab material in all
locations where the foundation was built at different times (such as additions).
Subslab radon test
Soil gas radon measurements may be taken beneath the slab in slab on grade or
basement buildings or wings. This has some value in understanding radon sources
and locating "hot spots" that could affect the choice of locations for ASD suction
points. EPA has found typical subslab radon levels that varied from 200 pCi/L to
8,000 pC/L, with a mean of 1,500 pCi/L. These radon levels would be incredibly high
if they were measured in room air, but are normal subslab radon concentrations,
even for buildings with radon levels near 4.0 pCi/L.
Some radon measurement equipment can be used to take short term radon
measurements at suspected entry points. This technique of radon "sniffing"
provides information about the relative importance of different entry points.
6-22
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Detailed Investigation
Vacuum test of pressure field extension
The material beneath the slab is often sand fill or sand and gravel that was native
to the site. In many buildings, a layer of crushed aggregate is placed over the native
material. This feature provides a plenum-like space that makes it easy for an ASD
system to depressurize below the slab and create a negative pressure field.
The vacuum test or vacuum test of pressure field extension involves drilling
several holes through the slab, putting suction on one hole, and observing the effect
on air movement at the other holes. A shop vacuum cleaner with a variable speed
control is used to assess the air flow resistance of the subslab material and the
distance that a low pressure field can be extended from the suction point. This
information can be used to determine the number and location of suction points and
to evaluate the fan performance characteristics that are important if ASD is the
chosen mitigation strategy.
Generally, the less air that can be drawn from under the slab, the more difficult it
is to extend a low pressure field beneath the slab. Low air flows (10 - 20 cfm or less)
usually indicate that more suction points are needed for a successful soil
depressurization system. However, it is also possible to find low air flows with
excellent pressure field extension, when: 1) a layer of coarse subslab aggregate
overlies impermeable soils, 2) the slab is tightly sealed, 3) the exterior foundation is
tight, and 4) there are no air bypasses (such as uncapped masonry walls) extending
through the slab.
At the other end of the spectrum, a vacuum test that finds little or no resistance to
air movement indicates one or more of the following possibilities: 1) there is a leak
in the slab near the test location, 2) the foundation and subslab soil are extremely
permeable, 3) there is an unknown air pathway. Any of those conditions are also
obstacles to pressure field development. In the second case, where there is little or
no resistance to air flow, it is critically important to seal holes in the slab to support
the operation of the ASD system.
6-23
-------
Detailed Investigation
This photograph shows a building investigator conducting the vacuum test. The suction hole was
drilled away from the wall to avoid running into a subslab footing.
Vacuum, tests should be performed in each wing of the building (i.e., in the
original building and each addition), usually in the rooms with the most elevated
radon levels. There is a risk that a limited sample will find areas that are not
representative of the school in general, or even of the room in which the tests are
being made. For example, soil conditions near perimeter footings may be different
from soil conditions under the middle of the slab. NOTE: Fill the drilled holes when
the vacuum test is completed. Polyurethane caulk is typically used to fill the holes.
6-24
-------
Detailed Investigation
ROOM A
j vacuum cleaner
, test holes
wall
ROOMB
f test hole
O
31 cfm suction
61 cfm suction
sub slab footing
10 20
Distance from suction point (ft.)
Figure 6-5: Vacuum Test of Pressure Field Extension
The upper part of this figure represents a cross section of a floor slab during a subslab vacuum test,
showing the locations of the suction point, four test holes, and a subslab footing. The graph shows
that the negative pressure field under the slab is strongest near the suction point. The pressure
differential drops off with increasing distance from the suction point. Lines have been drawn to
show the strength of the pressure field as a curve These lines stop at the test hole just to the left of
the subslab footing, because the footing interrupts pressure field extension. At the far right test
hole, the pressure under the slab is slightly higher than the pressure in the room, an indication that
radon may be entering the building. Although it might be possible to correct a radon problem in
Room A with a single ASD suction point, a second suction point would be needed to treat Room B.
Figure 6-5 illustrates the results of a typical vacuum test. Sample Working
Floorplan 9 on page 6-36 shows the results of diagnostic radon measurements and a
vacuum test of pressure field extension for the sample building illustrated in earlier
floorplans.
6-25
-------
Detailed Investigation
b. Building shell inspection and diagnostic testing
The more openings there are in a building, the more air must be supplied to
maintain pressurization. A walkthrough inspection can help to determine whether
building occupants are using operable windows and exterior doors for outdoor air
ventilation and temperature control. Devices such as automatic door closers can
serve as a reminder that doors should be kept closed. However, pressurization will
not work if the doors and windows are used to maintain comfort conditions.
Chemical smoke or, often, a simple visual inspection can identify leaks (e.g.,
at window sashes) that would need to be sealed to support a pressurization system.
These leaks will be most obvious during a fan door test.
Fan door test
The leakage area through the building shell determines how much outdoor air is
needed to slightly pressurize the building. The leakage area can be estimated using a
fan door test. Fan door tests are made by depressurizing or pressurizing the building
with several different air flows. One or more calibrated fan doors can be used to
provide the needed air flows. The difference in air pressure between the inside and
outside of the building is measured for each different air flow. The data collected
should form a curve that clearly shows the amount of air needed to pressurize the
building.
6-26
-------
Detailed Investigation
This photograph shows a fan door
test. The fan and its adjustable frame
completely fill the exterior door
opening shown in the background.
Doors and windows throughout the
building are closed during the test.
Pressure gauges (shown in foreground)
indicate air pressures in the building
and outdoors at different fan speeds.
Because the fan performance (cfrn at
different rotation rates and static
pressures) is well-documented, the
test results can be used to calculate
the "tightness" of the building. In
large buildings, two or more fan doers
may be required for this test.
Figure 6-6 illustrates the results of fan door testing.
Pressure differential measurements
Pressure relationships between the inside and outside of the building are one of
the key variables to study during the detailed building investigation. Slight positive
pressures (as low as +.001 inches water column) help to keep radon out of the
building. Negative pressures cause increased radon entry. A sensitive differential
pressure gauge (micromanometer) is used to measure indoor-outdoor pressure
differentials at penetrations through the slab or through the crack in a closed door or
window. Pressure differential measurements help investigators to assess the
potential for ASD and pressurization.
6-27
-------
Detailed Investigati
45000 -,
40000 -
35000 -
| 30000 -
*3>
1 25000 -
jjj 20000 -
15000 .
10000 -
5000 -
0
0
on
Building 1
D Building 2
. .
- ซ
n D D D
1 1 1
III
10 20 30
Pressure difference (pascals)
Figure 6-6: Fan Door Test Results
The fan door test results for these two buildings show that, assuming the same pressure
difference, much more air would move into (or out of) Building 1 than Building 2. It is
not possible to determine from these results alone whether Building 1 is leakier than
Building 2, because the volume of the two buildings must be taken into account.
Open interior (room) doors can interfere with intended pressure differentials.
They may also indicate occupant discomfort due to excessive temperatures or
stagnant air. Pressurization can only be a successful mitigation technique if it is
possible to maintain the desired pressure relationships by minimizing uncontrolled
openings.
Measuring the indoor-subslab pressure differential through the test hole that was
drilled for the vacuum test can reveal whether the building is running strongly
negative. The negative pressure exerted by the building's exhaust fans can compete
with the suction applied to the subslab material. A larger ASD fan can be selected to
compensate for this effect. In some cases, however, a soil depressurization system
will only work if exhaust fan suction is reduced, either by reducing the amount of air
exhausted from the building or by supplying more outdoor air to the building. You
may need to consider reducing negative pressures if the building is 5 or more pascals
(0.02" W.C.) negative relative to the subslab.
6-28
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Detailed Investigation
Measurements taken through exterior walls are very sensitive to outdoor wind
pressures. To assess the outdoor air pressure, it is always wise to make pressure
difference measurements across walls on all orientations and average the results. If
the mechanical equipment does not dramatically pressurize or depressurize the
building, a windspeed greater than a few miles per hour can obscure the effect of the
mechanical equipment. Postpone pressure difference measurements until calm
conditions exist.
The micromanometer
(differential pressure gauge) at
left is being used to assess the
indoor/outdoor pressure
differential. The reading shows
the building interior running
0.115 inches W.C. positive
relative to outdoors.
6-29
-------
Detailed Investigation
c. Ventilation inspection and diagnostic testing
During the initial investigation, available tools and expertise are used to identify
ventilation system problems. This could mean anything from a simple visual
inspection (e.g., Is the fan motor missing? Are the outdoor air intakes blocked?) to a
detailed assessment of equipment condition, control sequencing, and air flows.
During the Detailed Investigation, the team should finish collecting relevant
information about the ventilation system condition and operation. For example, an
HVAC engineer should inspect the condition of the ventilation system to identify
needed repairs and confirm that equipment has enough capacity to condition
additional outdoor ventilation air. The general condition of the HVAC system helps
to indicate whether pressurization or dilution are practical approaches to mitigation,
because both strategies require a long-term commitment to good maintenance. Key
equipment items are:
outdoor air intake - maximum air flow in full open position
heating coils (and heating plant) - maximum outdoor air flow that can be
heated under design conditions
cooling coils (and cooling plant) - maximum outdoor air flow that can be
cooled and dehumidified under design conditions
* supply fans - total powered supply cfm
exhaust fans - total powered exhaust cfm
Building investigators should evaluate the ventilation control strategy, the
method used to turn on and control the amount of outdoor air ventilation. Typical
strategies for controlling outdoor air entry are:
manually opened windows
manually operated individual or master switches for outdoor air dampers
time clock switches for outdoor air dampers
computer controlled switches for outdoor air dampers
HVAC equipment must be observed to see whether it is actually operational,
operates on schedule, and produces air flows that are close to design quantities.
Simple observations such as checking the position of an outside air damper blade or
the direction of air flow with chemical smoke can identify obvious malfunctions.
6-30
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Detailed Investigation
However, a more sophisticated ventilation evaluation is required to measure or
estimate actual air flows.
<''*^&Z?$g.{&'VK^^
7N9^l>erew#j^
^uldporairM^
Ventilation evaluation
To evaluate the adequacy of outdoor air ventilation, investigators must measure
or estimate the flow of outdoor air into the building. This will also make it possible
to evaluate dilution as a potential mitigation strategy, using the equation presented
on page 6-7.
As previously mentioned, ASHRAE Standard 62-1989 (now being adopted into
many codes) recommends a minimum of 15 cubic feet per minute (cfm) outdoor air
ventilation per person in classrooms.
One way to estimate outdoor air flow is to measure carbon dioxide
concentrations. The building's human occupants are a source of carbon dioxide
(CO2) and water vapor, which are given off when they exhale. People produce CO2 at
a predictable rate, depending on the activities they are engaged in. Elevated CO2
concentrations may indicate that an area is not being supplied with adequate outdoor
ventilation air.
6-31
-------
Detailed Investigation
The photograph at left shows a
carbon dioxide sensor. This is an
"active" sampler (with an ak pump).
"Passive" sensors (without pumps)
have a slower response time, but are
generally less expensive.
The carbon dioxide concentration in an occupied classroom depends on the
number of people in the classroom, the length of time they have been in the room,
the outdoor air ventilation rate, and the outdoor CO2 concentration. Carbon dioxide
readings taken in classrooms either before lunchtime or during mid-afternoon
(before school lets out) can be used to estimate the outdoor air ventilation rate on the
day of the measurement. Levels of 1000 ppm or lower are expected if outdoor air
ventilation rates meet the current ASHRAE standard of 15 cfm outside air per
person. EPA researchers have found COz levels in schools ranging from 500 ppm to
5,000 ppm. In general, the higher the CO2 level for a given occupancy, the lower the
outdoor air flow. Figure 6-7 can be used to estimate the outdoor air ventilation rate
for different COz concentrations, assuming that CO2 levels have come to equilibrium
(stabilized). NOTE: It can take many hours for carbon dioxide to reach equilibrium
in buildings with low outdoor air flows. While COi levels over 1000 ppm are a
strong indicator of low outdoor air ventilation rates, areas with COi concentrations
below 1000 ppm can still have outdoor air ventilation problems.
6-32
-------
Detailed Investigation
1
SH
!
A
IH
1
0
60
50
40 -
30 -
20 -
10 -
n -
\
1
\
\
^
V
V- A_A .
* * ~4 t-4-4 A A A A
1 1 1 1 1 i i T T *~T~^ 1
1000 2000 3000 4000
Carbon Dioxide (ppm)
5000
Figure 6-7: Carbon Dioxide as an Indicator of Ventilation
This figure shows carbon dioxide concentrations at different outdoor air ventilation
rates. It is important to note that measured carbon dioxide concentrations represent the
dynamic balance betweeen carbon dioxide production (exhaled breath) and removal
(dilution by outdoor air). The carbon dioxide concentration in a space does not reach
equilibrium until the occupant population and the outdoor air ventilation rate have
remained constant for 5 air changes.
A better way to assess the outdoor air flow rate is to measure or estimate: 1) the
fan-powered ventilation rate (or total airflow) and 2) the percent of the total air flow
that is made up of outdoor air. The fan-powered ventilation rate includes both
outdoor air and air that is withdrawn from an area and then recirculated.
6-33
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Detailed Investigation
The best way to obtain the fan-powered ventilation rate is to measure actual air
flows. Air flows in ducts are measured using a pitot tube or hot wire anemometer
traverse. Air flows at grilles and diffusers are measured using flow hoods. These
measurements should be performed only by experienced people.
This building investigator is using a flow hood at
the outdoor air intake for a classroom unit
ventilator. When the cloth "sleeve" of the flow
hood is held tightly against the wall or ceiling, it
channels air through a sensor grid that measures air
flow.
The percentage of outdoor air can be obtained by taking measurements of either
carbon dioxide or temperature in three locations: 1) the outdoor air (preferably near
the intake), 2) the return airstream, and 3) the mixed airstream. (See Figures 6-8 and
6-9.) For either of these techniques, the results will be more accurate when there is a
large difference between the airstreams. If temperature measurements are used,
multiple readings must be taken at each airstream to obtain an average, and the
mixed air must be measured before it is heated or cooled. Access problems can make
this impossible in some HVAC systems. Tt is very important to obtain multiple
measurements at different points in the mixed airstream. Stratification of the
outdoor air or return airstreams can distort calculations of the average mixed air
temperature.
Figures 6-8 and 6-9 show the equations used to calculate the percent of outdoor air
and the outdoor air ventilation rate in cfm/person.
Sample Working Floorplan 9 on page 6-36 shows the results of the building
inspection and diagnostic testing in an example school.
6-34
-------
Detailed Investigation
Figure 6-8: Calculating the Percent of Outdoor Air
Using temperature measurements:
Outdoor air (percent) =
-
return air
~ T
A
mixed air
x 100
T
A
return air A outdoor air
Where: T = temperature in degrees Fahrenheit
Using carbon dioxide measurements:
c - c
Outdoor air (percent) = ง L
X 100
Where: C s = ppm of carbon dioxide in the supply air (if measured in a
room), or
C s = ppm of carbon dioxide in the mixed air (if measured at an air
handler)
C r = ppm of carbon dioxide in the return air
C = ppm of carbon dioxide in the outdoor air
Figure 6-9: Converting % Outdoor Air to CFM/Person
The outdoor airflow (in cfm) can be calculated from the percent of outdoor
air and the total airflow:
Outdoor airflow (cfm) = Total airflow (cfm) x % Outdoor air
The outdoor airflow in cfm per person can then be calculated for
each room or zone.
Outdoor airflow (cfm/person) = Outdoor airflow (cfm)
Number of occupants
6-35
-------
Detailed Investigation
Sample Working Floorplan 9
1975 original - slab on grade j 1985 addition - over crawlepace
suction
i closet)
/ suction
OJO&" W.C.
/ at20feet\
'eturn plenum (no
ducts); block wall
ends above
drop ceiling; block
cores are open
at SO feet
diagnostic radon
r measurements
(short-term)
5-10 pCi/L in
room air ,
5O-200 pCi/L in block wall cores (5'-O" above floor) J \
This fioorplan builds on previous Sample Working Ftoorplans by showing the results of the building inspection
and diagnostic testing. NOTE: Not all of the diagnostic tests described in the text were needed in order to identify
appropriate mitigation strategies for this building.
A single suction point (for the vacuum test of pressure field extension) was adequate for (he three classrooms
because they are adjacent, were built at the same time, and have a common foundation system. The results indicate
good pressure field extension. The vacuum test of pressure field extension conducted in the Art and Music area is
less promising for ASD. In addition, investigators looked above the drop ceiling and observed that 1) the
masonry wall ends above the ceiling and 2) the masonry block tops are open. Diagnostic radon measurements
show higher radon levels inside the block cores than in the room air. This indicates that negative pressure in the
return plenum is drawing radon up the wall and into AHU-2, which blows it into the Art and Music rooms.
Based on these results, it appears that ASD will be a successful mitigation strategy for the classrooms. In the Art
and Music rooms, it is important to prevent the ventilation system from mining soil gas. If the block wall is easily
accessible and in good condition, it may be possible to correct the radon problem by sealing Ihe block cores.
Another option is to install return ductwork (seal seams carefully).
6-36
-------
Design and Implementation of Mitigation Techniques
7.0 Design and Implementation of Mitigation Techniques
This section provides an overview of design and implementation considerations
tor each type of radon mitigation system that is used in school buildings It is
intended to help you understand and oversee the work of the radon mitigation
contractors, HVAC contractors, test and balance firms, and HVAC control
contractors who will be involved in the actual installation work.
As you consider alternative ways to reduce radon concentrations in vour
buildmg, remember that control of radon requires a long-term commitment
Consider the following criteria:
effectiveness
permanence
durability
installation and operating costs
conformity with codes
reliability
maintenance
occupant comfort
ability to institutionalize the solution
ease and likelihood of defeating the mitigation system
self'exPlanatory' the last ^o deserve further
ฐf
Ability to institutionalize the solution: Any mitigation approach will require
periodic inspection and maintenance that must be integrated into normal building
operations. It may be necessary to develop new inspection checklists or staff training
programs. Operating manuals that explain how the radon control system is
intended to function should be provided to current facility staff and incorporated
into the orientation of new staff members. An alarm system should be installed to
provide a warning if the system fails. i^cmea to
Ease and likelihood of defeating the mitigation system: Systems that can easily be
defeated (either knowingly or unknowingly) create potential problems For
example, open doors and windows can defeat a mitigation system based on building
pressunzation. Mitigation approaches based on dilution can be defeated if possible
energy savings are given a higher priority than proper outdoor air ventilation
7-1
-------
Design and Implementation of Mitigation Techniques
Monitoring the Radon Mitigation System , , , V
Facility staff must understand the operating principle of the radon negation* system, - ,
recognize its critical components, and be attentive to its proper functioning, A variety of -
sensors, monitors, and alarms can be installed to check the performance of the rmtigation -
system and set off alarms if the system is not working. For mitigation gategtes **ซ***ป ,
Se ventilation system, sensors and monitors can be integrated with the HVAC control system.,
However, it is important that someone assume responsibility for checking those sensors,
monitors and alarms regularly. , '
Monitoring Airflow: Dilution-based mitigation systems function by increasing outdoor air flow
into the building. It is important to measure the actual air flow, if possible, rather than .
basing an estimate on the position of the outdoor air damper. Small differences in damper
position can have a large effect on air flow. Mr monitoring stations, temperature sensors, pt
pressure sensors can be used to measure actual outdoor air flow/dependmg.on the ventilation
system layout. , ,- '
Monitoring Pressure Differential: Pressurization or ASD-based mitigation systems function by
maintaining the appropriate pressure difference between the occupied space and the suh^floor,
area (soil below the slab, crawlspace, or utility tunnel). Pressure sensors are necessary to /,,,
monitor pressure differentials.
Alarms: Visible or audible alarms should be installed to notify operators if the mitigation -
system is not functioning properly. If your mitigation system operation is affected by -
ventilation system cycling you may want to interlock Je alarm system Wife your^timeBlocks
Checking the alarm should become a routine responsibility of facibiy staff. Make sure that, it
is possible to confirm the proper operation of the alarm system itself.,
T,?beTing the Radon Control System
The components of the radon mitigation system should be clearly labeled so that facility staff
and outside contactors will recognize its importance. Labels should identify the components
as part of the radon control system and should indicate desired air flow directions. Addresses
and telephone numbers for service personnel should be attached securely in a prominent
location The name and phone number of the facility staff person who.is responsible for the,
system should also be listed. ,
HVAC system problems sometimes arise when system components are serviced, altered; or. =
replacedV workers who are unaware of their intended function (e.g., fans installed.
backwards so that they exhaust air, rather than supplying it). Labels that identify system
components and air flow directions can help prevent this type of problem. -,,/.;'
7-2
-------
Design and Implementation of Mitigation Techniques
7.1 Active soil depressurization
Active soil depressurization (ASD) is the most widely-used approach to radon
mitigation in residences and has proven to be an effective technique in schools as
well. As described in Section 6 of this document, an ASD system creates a negative
pressure field beneath the slab, under an installed membrane, or in a crawlspace or
utility tunnel. When the system is functioning properly, soil gas is unable to enter
the occupied space. Instead, air tends to leak out of the building through any
unsealed cracks and holes in the slab. The negative pressure field reverses the
direction of soil gas air flow so that radon is drawn out from under the slab and
exhausted to outdoors.
a. System Components
ASD systems consist of the following components:
exhaust fan(s)
a concrete slab or an installed membrane
one or more suction points, with a suction pit beneath each suction
point
low pressure ducts to connect the fan and the suction points
exhaust outlet(s)
labels to identify components as part of a radon control system
monitor and alarm to signal system failure
fire control dampers (if ducts penetrate fire-rated barriers)
Exhaust fan(s): In-line centrifugal fans are typically used for soil depressurization
systems. The fans can move enough air (up to 200 - 700 cfm at the high flow end of
the performance curve) and create, enough suction (1.5 to 3 inches water column at
the low to middle flow end of the performance curve) to meet most soil
depressurization needs. In-line fans are easily attached to ducts. The fan(s) should
be located outside of the occupied space (preferably outside the building and above
the roof line) and as close as possible to the exhaust outlet. This design strategy
helps to keep radon-containing air from leaking into the building by keeping the
pressurized section of ductwork (i.e., the section of ductwork from the fan to the
discharge) outside of the building.
Concrete slab or installed membrane: An ASD system functions by reducing the air
pressure in the soil or fill material so that it is lower than the air pressure in the
building. A negative pressure field can only be developed and sustained if there is a
barrier between the soil and the occupied space.
7-3
-------
Design and Implementation of Mitigation Techniques
Suction point(s) and suction pit(s): The ASD fan exerts suction at holes drilled
through the slab (or openings in the installed membrane). Suction pits (created by
removing soil beneath each suction point) improve pressure field development by
reducing resistance where air velocity is highest and minimizing the total static
pressure drop in the system.
Low pressure ducts: Schedule 40 PVC pipe is commonly used for ducts in soil
depressurization systems. It is easy to find, easy to work with, and does not corrode.
Depending upon the duct routing, PVC may not meet fire code requirements for
installation inside the building, in which case steel is normally used. Whatever
material is selected, careful sealing at joints is needed to support pressure field
development. Condensation will occur inside ASD ductwork, so duct materials
must be chosen to resist damage from condensation.
Exhaust outlet: Exhaust outlet(s) for radon control systems should be located a
minimum of 10 feet above ground level, and a minimum of 10 feet from outdoor
air intakes, operable windows, or doors. Exercise care when locating the exhaust
outlet; it should be placed far enough away from air intakes to ensure that radon-
containing air does not re-enter the building.
Labels: Any radon control
system must be labeled as
such. If the system is not
clearly labeled, its purpose
may be forgotten as the
component '"'* 1ป-Jl^M' '.%ซ;! people managing the
n removal
-------
Design and Implementation of Mitigation Techniques
Monitors and alarms: The personnel managing the building need to know that the
system is working. Monitors generally sense pressure differentials in the ducts of
the ASD system or between the subslab area and the occupied space, with alarms or
lights to indicate malfunctions of the radon control system.
The "U"-shaped loop at left is a liquid
manometer mounted on the ductwork of an ASD
system. When the ASD system is functioning
properly (as in this photograph), the liquid
reaches higher on one side of the "U" than on
the other. The difference in height between
the two sides indicates the pressure
differential between the inside of the duct and
the room. Note: The duct is clearly labeled as
being part of a radon control system, and
includes the installer's telephone number.
The photograph at right illustrates another
pressure sensor used in ASD systems. Each
pressure sensor in this system feeds information
to a central location. By contrast, the sensor
design shown above requires staff to walk
through the building and examine each
manometer in its installed location.
7-5
-------
Design and Implementation of Mitigation Techniques
The lights along the bottom of this
box indicate that the ASD system
fans are operating. The fans are
intended to operate continuously, so
the ASD system should be checked
whenever any of the lights go out.
NOTE: If the indicator lights were
designed to be "off" under normal
conditions and turn "on" as a sign of
trouble, a burnt-out indicator bulb
could leave occupants uninformed of
an ASD system failure. With this
design, a burnt-out bulb sends a
false alarm that is easy to identify
and correct.
Fire control dampers: Fire control dampers may be required as part of the ASD
system design. For example, walls between corridors and rooms are considered fire
walls, and any penetrations through those walls must comply with fire codes. Note:
Many radon mitigation contractors may be unfamiliar with the code requirements
that govern non-residential buildings such as schools. An engineer with experience
in school HVAC systems should review the design of the radon mitigation system
for conformance with codes.
b. Design Considerations
Most radon mitigation contractors are more familiar with ASD systems than
with other techniques. This mitigation strategy is adaptable to a wide range of
building designs and can be successful in treating buildings with high or low pre-
mitigation radon concentrations. Figure 2-2 on page 2-11 and Figures 6-1 and 6-2 on
page 6-5 show typical ASD system designs. NOTE: ASD in a school building
involves different design considerations from ASD in a single-family home. Your
radon mitigation contractor should work with an HVAC engineer to design any
school ASD system, so that these differences are taken into account:
Building and fire codes: Building and fire codes that apply to schools are very
different from those that apply to single-family homes. State and local code
requirements should be investigated to make sure that the system design,
materials, and installation are in compliance.
7-6
-------
1
Design and Implementation of Mitigation Techniques
Negative pressure influences: The ASD system can only prevent radon entry
as long as the air pressure beneath the slab is lower than the air pressure in
the occupied space. Strong negative pressures in the building (such as large
exhaust fans) can sometimes overpower an ASD system. Mechanical
ventilation systems are a source of negative pressure that differentiates
schools from most homes. The school's HVAC system may require
adjustment to reduce negative pressures and allow the ASD system to
function properly. Sealing leaky air distribution ducts can help to bring
HVAC systems into proper balance and reduce negative pressures in the
building.
Subslab obstacles: Schools are more likely than single-family homes to have
obstacles beneath the slab such as interior subslab walls and footings.
Multiple suction points may be necessary to ensure pressure field extension
to areas surrounded by subslab walls.
Sealing is recommended to reduce leakage between the occupied space and
the area beneath the slab (or between the occupied space and the crawlspace).
Excessive leakage can make it difficult or impossible to maintain a negative
pressure field.
The photograph at left shows an ASD outlet on a school
rooftop. It has been located away from outdoor air
intakes. When an ASD system is designed for any
building, the ASD outlets should be placed to keep radon
from re-entering into the building.
7-7
-------
Design and Implementation of Mitigation Techniques
7.2 Pressurization
Pressurization and ASD both create a pressure gradient that blocks radon entry
into the building by maintaining a higher pressure within the building than
beneath the slab. Instead of withdrawing air from beneath the slab to create a
negative pressure field, pressurization functions by blowing enough additional
outdoor air into the building to maintain a higher air pressure indoors than
outdoors.
A mitigation system can work by pressurizing the sector(s) of the building that
contain elevated radon or by pressurizing the entire building. Pressurization of
individual rooms is generally impractical, because it may be impossible to maintain
a room under positive pressure when the door is open and impossible to
institutionalize a policy of keeping doors closed.
a. System Components
Pressurization of the occupied space requires the following components:
outdoor air intake
supply air fan(s) and heating and/or cooling coil(s)
ducts to distribute supply air
monitor and alarm to signal system failure
fire control dampers (if ducts penetrate fire-rated barriers)
This strategy is most economical if existing equipment can be used. Most
modern school buildings are designed to operate at a neutral or slightly positive
pressure with respect to the outdoors, a design strategy which helps to control drafts
and maintain comfort conditions. In such buildings, restoring the HVAC system so
that it functions according to its original design can often reduce radon below 4
pCi/L. However, if the amount of air leakage or the rate of powered exhaust is
higher than anticipated in the design, a higher outdoor air flow rate may be needed
to achieve a positive pressure in the occupied space.
b. Design Considerations
Pressurization requires the introduction of enough mechanically-supplied
outdoor air into the occupied space to counteract the negative pressures exerted by
the stack effect and the building's exhaust fans. The amount of additional air
7-8
-------
Design and Implementation of Mitigation Techniques
needed for successful pressurization thus depends on the amount of air that is
exhausted or leaks out of the building.
Sealing: Tight building construction supports successful pressurization.
Consider sealing to help reduce leakage from the space that is being
pressurized. Locations to seal could include leaky windows,
unweatherstripped exterior doors, and utility penetrations. Interior sealing
may be needed as well, including the installation of automatic door closers.
Air distribution: Proper air distribution within the area to be pressurized is
important to ensure success. Check air flow patterns and pressure
relationships using chemical smoke.
HVAC system capacity: If the HVAC system is modified to increase the flow
of outdoor air beyond original design quantities, greater heating or cooling
capacity may be needed. An HVAC engineer can analyze the costs and
benefits of a heat recovery system, which could provide energy savings and
enhance the capacity of your existing coils.
Figure 7-1 illustrates mitigation by pressurization.
7-9
-------
Design and Implementation of Mitigation Techniques
,Outlet for fan-powered
or convection exhaust
Motorized
dampers
Keep door closed
to ensure
pressurization
Outdoor
air
Heating and/or
cooling coils
Outdoor
air damper
control
Supply air
Transfer grille may need to be
*3ฃ closed to ensure pressurization
Pressure sensor sends signal to
control system and alarm
pressurizaton
Keep operable
windows
closed to
Figure 7-1: Mitigation by Pressurization
This mitigation strategy counteracts the negative pressure effects of exhaust fans and
natural convection by increasing the flow of mechanically-supplied outdoor ak into the
building (or, in some buildings, by reducing the amount of general exhaust). The black
arrows in the diagram above show air flow patterns. The white arrows show
pressurization in the room. Radon cannot enter as long as the air pressure inside the
building is higher than the air pressure under the slab. Doors and operable windows
must remain closed to ensure pressurization.
A pressure sensor, located away from exterior walls to minimize wind effects, measures the
indoor/subslab pressure differential. The pressure sensor provides information to the
control system, which regulates the flow of outdoor air by adjusting the motorized dampers.
The alarm notifies occupants if the system fails to maintain the desired pressure relationship.
7-10
-------
Design and Implementation of Mitigation Techniques
7.3 Dilution
Dilution works by increasing the percentage of outdoor air in room air. In
theory, doubling the outdoor air flow would reduce radon to 1/2 its original
concentration, quadrupling the outdoor air flow would reduce radon to 1/4 its
original concentration, and so on (see the formula in Section 6, page 6-7). In reality,
however, the relationship between the outdoor air flow and the indoor radon
concentration is also affected by air distribution patterns and pressure relationships.
The combined effect of these influences on radon concentrations must be measured
directly because it varies from situation to situation.
If your building relies on exhaust fans to draw outdoor air into the building (as
make-up air), raising the rate of exhaust could successfully dilute the radon.
However, raising the exhaust rate also increases the tendency for the building to run
negative, which could draw in more radon. If your school has mechanically-
supplied outdoor air, an increase in outdoor air flow might reduce negative
pressure in the building, lowering the radon level further than the formula would
predict.
The design outdoor air flow in many school buildings is 5 cfm/person, only 1/3
of the outdoor air ventilation rate currently recommended by ASHRAE. Correcting
gross HVAC system problems as discussed in sections 3 and 4 may still leave
outdoor air flows at 5 cfm/person or less.
If radon levels tested at less than 10 pCi/L with an outdoor air flow rate of 5
cfm/person or lower, mitigation by dilution may be a practical approach for your
building. The increased flow of outdoor air reduces radon concentrations and also
lowers the concentrations of other airborne contaminants that have originated
within the building.
NOTES:
1. Use of a dilution approach to radon mitigation is likely to increase energy
consumption. However, this increase in energy use may be offset by improved
efficiency of the HVAC equipment. Properly functioning controls, clean filters, and
clean coils can all help to reduce energy consumption.
2. The capacity of heating and cooling coils determines the quantity of outdoor air
that can be conditioned and could prevent meeting the recommendations of
ASHRAE Standard 62-1989.
7-11
-------
Design and Implementation of Mitigation Techniques
a. System Components
A mitigation system based on diluting radon in the occupied space requires the
following components:
outdoor air intake
fan(s) and heating and/or cooling coil(s)
ducts to distribute supply air
monitor and alarm to signal system failure
fire control dampers (if ducts penetrates fire-rated barriers)
As with pressurization of the occupied space, this mitigation strategy is most
economical if existing equipment can be used.
b. Design Considerations
Air distribution: Proper air distribution is important to the success of this
mitigation strategy. Do not assume that the air flows shown on mechanical
plans are correct; an experienced person should measure actual air flows.
HVAC system capacity: If the HVAC system is modified to increase the flow
of outdoor air beyond original design quantities, greater heating or cooling
capacity may be needed. An HVAC engineer can analyze the costs and
benefits of a heat recovery system, which could provide energy savings and
enhance the capacity of your existing coils.
* Pre-mitigation radon concentrations: Dilution alone is unlikely to be a
practical mitigation approach if the pre-mitigation concentrations are high.
EPA's experience suggests that other mitigation measures will be needed if
pre-mitigation radon levels are above 10 pCi/L.
Outdoor contaminants: The outdoor air must not introduce levels of
outdoor air pollutants that could cause indoor air problems.
Moisture considerations: The HVAC system must be able to remove enough
moisture from the outdoor ventilation air to maintain the indoor relative
humidity at a level that is comfortable and does not promote microbiological
growth (e.g., mold, mildew).
Figure 7-2 illustrates mitigation by dilution. Sample Working Floorplan 10
shows mitigation recommendations for the school shown in previous floorplans.
7-12
-------
Design and Implementation of Mitigation Techniques
=1
Outlet for
fan-powered
or convection
exhaust
Filter
Supply fan
Heating and/or
cooling coils
Motorized
dampers
3xhaust
grille
Corridor
'Supply air
"Transfer grille
Classroom
Radon enters the occupied space
through openings to earth such
as the floor/wall joint
\Outdoor
air damper
control -
interlock
with flow
sensor or
tensiometer
Figure 7-2: Mitigation by Dilution
This mitigation strategy increases the flow of mechanically-supplied outdoor air into the
building, mixing the outdoor air with room air to lower the concentration of radon and
other airborne contaminants. If the total volume of mechanically-supplied air is increased,
this strategy will also tend to reduce radon entry by counteracting the negative pressure
effects of exhaust fans and natural convection. The black arrows in the diagram show air
flow patterns.
The control system must maintain a minimum flow of outdoor air into the building to
provide the necessary dilution. A. flow sensor (which measures air flow) or a tensiometer
(which measures the damper opening) will set off the alarm if the flow of outdoor air is
reduced below the setpoint. Doors and windows can be opened without disrupting the
mitigation system; in fact, radon concentrations should be lower when windows are open.
Mitigation by dilution requires the ability to introduce and condition (heat or cool) an
increased flow of outdoor air. It is only a practical mitigation approach for schools in which
initial outdoor air flows and initial radon concentrations are both relatively low.
7-13
-------
Design and Implementation of Mitigation Techniques
Sample Working Floorplan 10
H985 addition - over crawlepace
Drill block wall
and blow In
polyurethane
foam to seal
block cores
across one
course
of blocks. To
confirm
successful
sealing,
measure
radon in cores
above sealed
course. As an
alternative (or if
sealing Is not
successful),
install ducted
returns (seal
seams).
Library/
Media
DOS
Stage
Mech. Rm.
009
Rms
Oil
Gym
012
Music
014
ftge
027
Install ASP
system with at
east one suction
oolnt per
classroom. Select
one or more fans
based on results
of vacuum test.
Confirm pressure
field extension
after
Installation.
Stor.
026
Potential ASP
layout shows duct
arrangement using
each ASP fan
serving two
classrooms.
Locate ASP fan
away from
.outdoor air Intakes
Classrm.
024
Classrm.
023
Classrm.
022
Classrm.
021
fe
T
015
Classrm.
017
Classrm. 1 Classrm.
018 1 019
Classrm.
020
I
This floorplan builds on previous Sample Working Floorplans by
showing the mitigation strategy for the three classrooms and the Art and
Music area. The notes indicate methods of assessing mitigation system
performance that will allow fine-tuning when the mitigation systems are
installed.
7-14
-------
Post-Mitigation Measurements
8.0 Post-Mitigation Measurements
This section provides guidance in performing post-mitigation measurements. It
provides specific guidance as to how the measurements should be performed and
eriod G g/S mechanical systems should be operated during the testing
After the mitigation system is in place and operating, test the radon
concentrations in each area that has been treated. Use professional radon testers
listed in EPA s RMP program or state-certified testers or school personnel who have
qZn7Prฐ? ? !f^d t0 rrfurn: the measurements. (See Radon Measurement in
Schools - Revised Edition for the level of training recommended.) The flowchart
below shows the recommended decisionmaking sequence.
Implement Mitigation
ASD with or
without dilution
or pressurization
TEST
CONDITIONS
HVAC on normal
occupied/unoccupied
cycle throughout test
Dilution or
pressurization
alone
TEST
CONDITIONS
HVAC on
occupied cycle
throughout test
Troubleshoot
mitigation system,
make modifications
or additions,
and retest
Record and maintain
outdoor air damper
settings
Yes
Conduct continuous
radon monitoring to
establish ventilation
start-up and
shut-down times
Institute a long-term
radon management
plan
Figure 8-1: Post-Mitigation Measurements
8-1
-------
Post-Mitigation Measurements
* Wherever ASD has been used as a mitigation strategy: Conduct radon testing in
keeping with EPA's measurement protocols. If radon measurements are
performed by a contractor, be sure the company is listed with EPA's RMP
program (or certified by your state). Either short-term or long-term
measurement devices may be used. Short-term devices have the advantage of
providing a relatively quick indication of whether the mitigation strategy is
successful; long-term devices provide results that are more representative of the
annual average radon level. Operate the HVAC system on its normal
occupied/unoccupied cycle, even if your mitigation strategy combines ASD with
pressurization or dilution.
. Where dilution or pressurization have been used without ASD: The radon test
results will be affected by HVAC equipment cycling. In order to determine
whether the ventilation system is controlling radon relatively quickly, EPA
recommends that you perform a short term radon measurement test following
EPA protocols and use test devices obtained from an RMP-listed organization.
The ventilation system must operate in the occupied cycle with outdoor air
dampers in the minimum position throughout the entire testing period. If the
test is performed when the ventilation system is operating on normal
occupied/unoccupied cycling, test results are likely to be higher than occupants
actually encounter during occupied periods (i.e., radon levels usually rise during
the unoccupied cycle).
8.1 Evaluate Results of Post-Mitigation Radon Measurements
Where the post-mitigation radon measurements show radon below 4 pCi/L, you
have brought the radon concentration under control.
_ Tf you are using ASD: Establish a long term radon management program (see
Section 9). NOTE: Remember mat radon concentrations are sensitive to air
flow patterns and air pressure relationships. Record and maintain outdoor,
return, and exhaust air damper settings, the timing of occupied and
unoccupied cycles, and the quantities of powered exhaust. Before making any
changes to the ventilation system, consider the potential effect on radon
concentrations.
_ If your mitigation strategy uses pressurization or dilution without ASD: You
have learned that the HVAC system can be used to control radon. Now you
need to adjust the HVAC system so that radon remains below 4 pCi/L
whenever the building is occupied. Figure 5-1 on page 5-3 shows how
8-2
-------
Post-Mitigation Measurements
occupied/unoccupied cycling affects radon concentrations in a typical school.
Within each ventilation zone, (room or rooms served by the same piece of
ventilation equipment), determine which room has the highest retest results.
In that room, use a continuous radon monitor (CRM) to collect continuous
radon readings for a minimum of 48 hours while the HVAC equipment
cycles normally. (NOTE: You may need professional assistance to obtain and
interpret continuous radon measurements.)
Use the CRM results to determine the ventilation system start-up and shut-
down times necessary to maintain radon levels below 4 pCi/L whenever the
building is occupied. Start the occupied cycle early enough for radon to drop
below 4 pCi/L by the time the first building occupants arrive. When you
have adjusted the timing of the control cycles, go to Section 9. Long term
radon management is critically important to prevent radon problems from
recurring in the future. NOTE: Record and maintain outdoor air damper
settings, the timing of occupied and unoccupied cycles, and any other
modifications that were made as part of the HVAC-based mitigation strategy.
Avoid any change to key HVAC components that might cause radon levels to
rise.
Areas in which the post-mitigation radon measurements show radon greater
than or equal to 4 pCi/L will require further attention. Review the operating
principle(s) of your mitigation strategy and discuss them with your HVAC
engineer, radon mitigation contractor, and other individuals who have been
involved in designing, installing, and operating the mitigation system. Conduct
a careful inspection of the mitigation system to confirm that all components
have been installed correctly and are functioning properly. Additional (or
improved) sealing or other adjustments may be needed to support the operation
of the mitigation system. Additional radon measurements, such as continuous
radon readings, can provide valuable periodic information concerning the effects
the HVAC system has on radon concentrations (e.g., occupied/unoccupied
cycling, use of large exhaust fans such as kitchen range hoods).
8-3
-------
-------
Long Term Radon Management
9.0 Long Term Radon Management
Unless you are aware of the conditions that can cause radon to enter your
building and remain vigilant in avoiding those conditions, your radon problems are
likely to recur in the future. This is relatively straight forward and need not be a
cause of alarm, but should remind you to plan seriously for long term management
of the radon problem. This section is designed to guide you through the important
components of a long-term radon management plan.
When the mitigation system is installed, it is important to obtain or create an
instruction manual. The manual should describe the function and operation of the
system, as well as recommended maintenance practices.
Earlier sections of this document have pointed out that HVAC systems require
regular maintenance in order to function properly and prevent indoor air quality
problems. Any new mechanical equipment that has been installed to correct radon
problems also requires periodic inspection and maintenance. Even radon
mitigation strategies that do not involve mechanical equipment, such as sealing, are
likely to need occasional repairs. In short, any. radon or indoor air quality plan
requires a long term management program.
9.1 Periodic Radon Testing
Many factors can cause indoor radon levels in your building to change over time
New openings to earth may develop due to settling, deterioration of the building
structure, or construction or renovation work. Pressure relationships can change if
the ventilation system becomes unbalanced or HVAC equipment is added,
removed, or replaced. These influences may produce elevated radon levels in
rooms in which the initial radon test results were below 4 pCi/L. Periodic retesting
of the entire school is important to be confident that your radon mitigation system
is functioning properly and that additional rooms have not developed radon
problems. EPA recommends annual retesting of all areas that have been mitigated.
The annual retest should be performed when the outdoor air dampers are most
likely to be at their minimum position (i.e., winter in northern portions of the
country, summer in southern areas).
NOTE: It may be important to adjust the start-stop times of HVAC equipment in
which case continuous radon measurements will be required.
9-1
-------
Long-Term Radon Management
Wherever ASP has been used as a mitigation strategy: Use test devices that are
listed in EPA's Radon Measurement Proficiency (RMP) program and conduct
radon testing in keeping with EPA's measurement protocols. Operate the HVAC
system on its normal occupied/unoccupied cycle, even if your mitigation strategy
combines ASD with pressurization or dilution.
Where dilution or pressurization have been used without ASD: The radon test
results will be affected by HVAC equipment cycling. If the test is done when
HVAC equipment is operating on normal occupied/unoccupied cycling, your
results will probably be higher than occupants actually encounter during
occupied periods (i.e., radon levels usually rise during the unoccupied cycle). To
avoid this distortion of the radon test results, operate the HVAC equipment on
occupied cycle 24 hours/day throughout the test period. In addition, outdoor air
(faTPpers should not be allowed to open any further than their minimum setting
during the test period: this simulates outdoor air ventilation during extreme
weather conditions.
9.2 HVAC System Maintenance
If you do not have a Preventive Maintenance (PM) program in place for the
HVAC system, EPA strongly recommends that you develop such a program. It is
possible to save energy through a conscientiously-applied preventive maintenance
program. The PM program must be properly budgeted and implemented, not
merely planned on paper, and may require additional funding for staff training and
development. HVAC system operators must have an adequate understanding of
the overall system design, its intended function, and its limitations.
The following general elements should be part of a PM plan:
Periodic inspection, cleaning, and service as warranted: Consult the operating
manuals for your mechanical equipment and develop a maintenance schedule.
Make certain that all items of mechanical equipment are included in the program.
Critical HVAC system components that require PM in order to maintain comfort
and deliver adequate ventilation include:
outdoor air intake openings
damper controls
air filters
drip pans
cooling and heating coils
fan belts
9-2
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Long Term Radon Management
humidification equipment and controls
distribution systems
exhaust fans
time clock settings (e.g., to correct for power outages, annual changeover
between standard and daylight savings time, and changes in building use)
Adjustment and calibration of control system components: HVAC systems should
be tested and balanced whenever remodelling or construction activity changes room
layouts, population density or airflow patterns. (See page 9-4 for more about testing
and balancing.)
After an appropriate "occupied-unoccupied" cycle has been selected and
instituted, inspect the controls periodically to confirm that the control system is
operating as intended. Time clock settings can slip gradually out of adjustment or
become disrupted by power outages.
Some professional and trade associations offer guidance that can help in
developing a preventive maintenance program. For example, the American Society
of Heating, Refrigeration, and Air-Conditioning Engineers' ASHRAE 1-1989:
Guideline for the Commissioning of HVAC Systems includes recommendations for
periodic maintenance. The Air-Conditioning and Refrigeration Institute (ARI)
offers Air Conditioning and Refrigeration Equipment General Maintenance
Guidelines for Improving the Indoor Environment. The Sheet Metal and Air
Conditioning Contractors' National Association (SMACNA) publishes a manual
entitled Indoor Air Quality and other related documents, including HVAC Duct
Systems Inspection Guide, HVAC Systems - Testing, Adjusting and Balancing and
HVAC Air Duct Leakage Test Manual. This listing of publications is provided for
your information and does not constitute an EPA endorsement.
9-3
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Long-Term Radon Management
Testing and Balancing ;
Problems during installation, operation, maintenance, and servicing of the HVAC system could prevent it from " '
operating as designed, increase operating costs, and decrease equipment life. Each systenxshould be tested periodically
and adjusted as needed to ensure its initial and continued performance. Testing and balancing involves the
testing adjusting, and balancing of HVAC system components so that the entire system provides airflows that are in
accordance with the design specifications. Ne.w design specifications may he. required if building usage or the
,^0,.^ relation have changed. Typical components and system parameters tested include: all supply, return,
exhaust, and outdoor airflow rates; control settings and operation; air temperatures; fan speeds and power , ,
consumption; filter resistance. , .
The typical test and balance contractor coordinates with the control contractor to verify and ensure the most effective
system operation within the design specifications, identify and correct any problems, and ensure the safety of the
system A test and balance report should provide a complete record of the design, preliminary measurements, and
final test data The report should include any discrepancies between the test data and the design specifications, along
with reasons for those discrepancies. To facilitate future performance checks and adjustments, appropriate records
should be kept on all damper positions, equipment capacities, control types and locations^control settings and
operating logic, airflow rates, static pressures, pressure relationships between zones, fan speeds/and .horsepowers. .
Effective balancing requires a skilled technician with the proper experience and instruments, Use of a test and balance
contractor who is certified by the Associated Air Balance Council (AABC) or the National Environmental Balancing
Bureau (NEBB) will help to ensure quality services. Defining test and balance work as a professional service '
exempts it from competitive bidding requirements, This allows schools to select the best-qualified firjn and pay for
necessary work on a time and materials basis rather than being obligated to acceptthe lowest .fixed bid. .
Construction or renovation projects: Testing and balancing should be performed during new construction
and when space is renovated or changed to provide for new occupancy. Testing and balancing provides a check on the
work of the mechanical contractor. If the HVAC system is properly adjusted, measured airflows, should bq within
10% of design quantities. However, measured airflows that seem to match design quantities exactiy should taise -,_
suspicions about the legitimacy of the test and balance report. < ' / ' '
To avoid conflict of interest, some engineers recommend that the test and balance firm work directly for ind report ,, .
directly to the owner, rather than subcontracting through the mechanical contractor. This approach can create -
coordination difficulties and make it difficult to allocate responsibility in case 'of problems. As an alternative^the ^
owner could hire a second, independent test and balance firm to "spot check" the work of the mechanical contractors
test and balance firm. , ,--',,-.;,,
Testing and balancing of existing building systems: Testing and balancing of,existing building systems
should be performed whenever there is reason to believe the system is not functioning as designed or when current ,
records do not accurately reflect the actual operation of the system. The Associated Air Balance Council (AABC) and
National Environmental Balancing Bureau (NEBB) recommend routine testing and balancing every 3-5 years. ;/.
An economical approach to testing and balancing existing systems.is to divide the job, into stages, A detailed; test' '
report for a school HVAC system should cost roughly $1,000 to $5,000, depending on.lhe size and, complexity^f the
system. The facility operator or the school's consulting engineers can then examine me report and issue bid, , ^ /-
documents that describe precisely what adjustments are needed. , ' ,, .'(,-"...
9-4
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Long Term Radon Management
9.3 Installation of New HVAC Equipment, Building Renovations
Renovations or the installation of new HVAC equipment can alter pressure
relationships within your building and disrupt or defeat your radon control strategy.
Structural modifications or additions could stress the existing slab and create or
enlarge openings to earth. Be particularly attentive when projects are likely to
depressurize the building. Examples include:
One or more new exhaust fans are being installed. Make certain that adequate
make-up air is provided.
The building shell is being tightened by replacing windows or doors or is
being air-sealed for energy conservation. This could reduce the infiltration
air available for your existing exhaust systems and also lower the ventilation
rate. Be careful to introduce and distribute adequate outdoor air to serve your
ventilation needs.
9-5
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-------
Special Considerations
10.0 Special Considerations
This section provides an overview of some considerations in regard to buildine
codes and worker protection. ซ"uuig
10.1 Building Codes
Building codes are intended to promote good construction practices and prevent
health and safety hazards. Trade associations such as the American Society of
Heating Refrigeration, and Air-Conditioning Engineers (ASHRAE) and the
National Fire Protection Association (NFPA) develop recommendations for
appropriate design and installation, and those recommendations are given the force
of law when adopted by state or local regulatory bodies. Contact your state Education
Department or a consulting engineer to learn about the code requirements that
apply to your school.
Code requirements are enforceable during construction and renovation-
however, those requirements change over time as code organizations adapt to new
information and technologies. In general, buildings are not required to modify their
structure or operation to meet changes in the codes. Indeed, many buildings do not
operate in conformance with current codes nor with the codes they had to meet
during construction. For example, the outdoor air flows that ASHRAE's Standard
r^?omf ^ ฐr JClaSSIฐฐmS Were reduced from 30 cfm/person to 10 cfm/person
in the 1930 s and reduced again to 5 cfm/person in 1973. Concern over indoor air
l^f^Sa reconsideration of the standard, so that its most recent version,
Standard 62-29*9, calls for 15 cfm/person. However, many schools that reduced
outdoor air flows districtwide in the 1970s continue to operate at outdoor air
ventilation rates of 5 cfm/person or less.
a. Building Codes and Radon Mitigation Projects
The participation of a registered engineer or architect may be legally required for
work affecting mechanical systems, structural components, and life and safety codes
Radon mitigation contractors whose experience has been limited to residential work
may not know the codes or standards that apply to schools.
Code requirements affect the selection of materials used for mitigation and the
way those materials are installed. Some system designs require the use of non
combustible ductwork rather than PVC. NFPA (National Fire Protection
10-1
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Special Considerations
Association) standards (Plastic Systems for the Removal of Non-Flammable
Corrosive Fumes) prohibit the use of plastic piping to penetrate fire-rated walls or
floors, although it can be routed through fire-rated shafts or fire-rated partitions.
Non-combustible materials are also required if ductwork is installed within an air
plenum, but PVC piping is acceptable for use in the space above a drop ceiling. Hre
dampers must be installed where ductwork penetrates fire rated barriers.
10.2 Worker Protection
Normal safety precautions observed during routine operation of the building
must be followed closely during radon and indoor air quality investigations. When
the investigator is not familiar with the mechanical equipment in that particular
facility, an operator or engineer should be present at all times in equipment areas.
Potential safety hazards include:
electrocution .
injury from contacting fans, belts, dampers or slamming doors
burns from steam or hot water lines
falls in ventilation shafts or from ladders or roofs
Investigators evaluating radon and indoor air quality generally do not encounter
situations in which specific personal protection measures (e.g., protective garments
and respirators) are required. However, safety shoes and eyeglasses are generally
recommended for working around mechanical equipment. Investigators may need
additional protection in the vicinity of certain building areas or HVAC equipment
when severe contamination is present (e.g., microbiological, chemical or asbestos).
Such decisions are site specific and should be made in consultation with an
experienced industrial hygienist. General considerations include the following:
Radon: Radon concentrations in unventilated areas with exposed earth (such as
utility tunnels and crawlspaces) or in sumps may be high enough to warrant the
use of a respirator in those locations. A respirator with HEP A (high efficiency
particulate air) and organic vapors filters is a common piece of protective
equipment for radon investigators, but cannot seal properly around facial hair.
Professional investigators who have not shaved their beards often use positive
pressure masks. If radon measurements are not being taken during the
investigation, ventilation of the work area with outdoor air is another effective
way to reduce worker exposure.
Microbiological: Care must be taken when serious building related illness (e.g.,
10-2
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Special Considerations
Legionnaire's disease) is under investigation or when extensive microbiological
growth has occurred. Investigators with allergy problems should be especially
cautious. The array of potential contaminants makes it difficult to know what
sort of personal protection will be effective. At a minimum, investigators
should minimize their exposure to air in the interior of ducts or other HVAC
equipment unless respiratory protection is used. If there is reason to suspect
biological contamination (e.g., visible mold growth), expert advice should be
obtained about the kind of respiratory protection to use and how to use it.
Possible protective measures against severe microbiological contamination
include disposable coveralls and properly fitted respirators.
Asbestos: A radon investigation often includes inspection above accessible
ceilings, in crawl spaces or utility tunnels, inside shafts, and around mechanical
equipment. Where material suspected of containing asbestos is present, the
investigator should take appropriate precautions. This might include disposable
coveralls and a properly fitted respirator. Many areas that contain asbestos are
labeled with instructions that should be followed.
Note: The requirements for proper fit, physical condition of the wearer, and other
considerations involved in selection of the proper respirator must be evaluated by
an occupational safety and health specialist. There is a NIOSH (National Institute
for Occupational Safety and Health) Respirator Decision Logic for proper respirator
selection, and OSHA (the Department of Occupational Safety and Health) has
regulations for an appropriate respirator protection program. EPA's RCP program
includes limited worker protection training for radon contractors. EPA's Radon
Mitigation Standards for residences (see Appendix B) discusses worker health and
safety.
10-3
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Glossary and Acronyms
Appendix A: Glossary and Acronyms
Glossary
Above-grade - Above ground level.
Active soil depressurization - A mitigation strategy that functions by withdrawing
radon-containing soil gas from below the building slab (or, in the absence of a
slab, from under an installed membrane) and exhausting it outdoors before it
can enter the building.
Aggregate (subslab)- Crushed stone, gravel, or other fill material placed in the
excavation before the building slab is poured.
Air exchange rate - Used in two ways: 1) the number of times that the outdoor air
replaces the volume of air in a building per unit time, typically expressed as
air changes per hour; 2) the number of times that the ventilation system
replaces the air within a room or area within the building.
Air flow monitoring station - An instrument that measures air volume.
Air handling unit - A device, usually connected to ductwork, to move air, which
also may clean and condition the air.
Anemometer - A device to sense and measure air velocity of air flow at a point.
Annual average (radon) exposure - Radon exposure averaged over one year.
As-built - In the construction industry, as-built plans refers to floorplans that have
been corrected to reflect differences between the original design and the actual
construction.
ASHRAE Standard 62 - the ASHRAE standard that, among other features,
establishes recommended outdoor air ventilation rates for different'building
uses. The current version is ASHRAE Standard 62-1989.
Backdrafting (of combustion appliances) - A condition where the normal
movement of combustion products up a flue is reversed, so that the
combustion products can enter the building.
Below-grade - Below ground level.
A-l
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Glossary and Acronyms
Biological contaminants - Agents derived from or that are living organisms (e.g.,
viruses, bacteria, fungi, and mammal and bird antigens) that can be inhaled
and can cause many types of health effects including allergic reactions,
respiratory disorders, hypersensitivity diseases, and infectious diseases. Also
referred to as "microbiologicals" or "microbials."
Blanks - In the context of radon measurement, blanks are unexposed measurement
devices sent for analysis along with exposed devices used as a means of
quality assurance.
Blower door - See fan door.
Building shell - Elements of a building that enclose the internal space, including
walls, windows, doors, roofs, and floors (including those in contact with
earth).
Carbon dioxide (CC^) - Carbon dioxide is a component of exhaled breath, and is
measured as an indicator of the outdoor air ventilation rate.
Carcinogen - A substance, exposure to which increases the probability of developing
cancer.
Commissioning - Start-up of a building that includes testing and adjusting HVAC,
electrical, plumbing, and other systems to assure proper functioning and
adherence to design criteria. Commissioning also includes the instruction of
building representatives in the use of the building systems.
Concentration - The quantity of a substance per unit volume.
Conditioned air - Air that has been heated, cooled, humidified, or dehumidified to
maintain an interior space within the "comfort zone." (Sometimes referred
to as "tempered" air.)
Contaminants (air) - Materials in the air that, at high enough concentrations, cause
undesirable health effects.
Damper - A device used to vary the volume of air passing through an air outlet, air
inlet, or duct often controlled by pneumatic devices.
Decay (radioactive) - The transformation of one radioactive element into another,
resulting in the release of radioactivity.
A-2
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Glossary and Acronyms
Diagnostics (radon) - Procedures used to identify or characterize conditions within
buildings that may contribute to radon entry or elevated radon levels or may
provide information regarding the performance of a mitigation system.
Dilution - Mitigation strategy that lowers the concentration of airborne
contaminants (e.g., radon) by increasing the fraction of outdoor air (e.g., air in
which the radon concentration is very low) in the supply air stream.
Duplicates - In the context of radon measurement, duplicates are multiple
measurement devices of the same type, exposed at the same location and over
the same time period for use as a means of quality assurance.
Dynamics - In the context of this guide, dynamics is used to describe patterns of air
flow of air (and the flow of airborne contaminants) into, through, and out of
a building.
Entry routes (soil gas) - Openings between the building interior and the ground.
Equilibrium - The point at which the entry (or creation) rate of a contaminant equals
the removal rate.
Exfiltration - Air movement out of an enclosed space (e.g., a building) through
cracks and openings.
Exhaust - Indoor air that is removed from a building. When indoor air is exhausted
from a building, outdoor air (including soil gas) infiltrates the building to
replace the exhausted air.
Fan coil unit - Fan and heat exchanger for heating and/or cooling assembled within
a common casing.
Fan door - A diagnostic tool for building investigations, sometimes referred to as a
blower door. A fan door includes a calibrated fan with a known performance
curve, pressure measurement devices, and a frame that allows the fan to be
placed in a door or window opening. Air flows and pressure differences are
measured at several fan speeds and used to calculate the leakage area of the
building.
Fan pressurization test - A diagnostic test conducted using a fan door.
Fire control damper - See fire damper.
A-3
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Glossary and Acronyms
Fire damper - Device that automatically interrupts air flow through part of an air
distribution system to restrict passage of flame. Installed in a fire-rated wall or
floor, a fire damper closes automatically in the event of a fire to maintain the
integrity of the fire-rated separation.
Fire rated wall/floor - A wall or floor system designed to separate areas for the
purpose of offering protection from fire and smoke.
Fill - Material placed in a building excavation before the slab is poured.
Flow hood - A diagnostic tool for building investigations. A flow hood measures air
flow at air outlets or inlets by directing the air stream through an air flow
monitoring station.
Flow sensor - A sensor that indicates air flow in a duct.
Follow-up (radon) testing - Testing designed to confirm the results of the initial
testing using identical testing devices and similar test conditions.
Footing - A concrete base, supporting a foundation wall, that is used to distribute
the weight of a building over the soil or subgrade underlying the building.
Foundation - The below-grade structure of a building.
Freeze stat - A safety device designed to protect heating and/or cooling coils from
freezing by shutting off outdoor air flow into a building below the device's
setpoint.
Grade - (usage: below-grade, above grade) Ground level.
Heatless chemical smoke - A tool for building investigations consisting of a
chemically-generated smoke that makes air circulation patterns visible.
Hydronic - An HVAC term, refers to heating system piping.
Indoor Radon Abatement Act - The legislation that establishes Federal radon policy
and directs the U.S. Environmental Protection Agency in its radon-related
activities.
Infiltration - Air movement into an enclosed space (e.g., a building) through cracks
and openings.
A-4
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Glossary and Acronyms
Initial (radon) testing - Testing designed to identify all regularly-occupied ground
contact rooms that may have elevated radon concentrations.
Institutionalize - Incorporate into normal operations.
Long-term (radon) testing - Tests that are more than 90 days in duration.
Make-up air - Air that enters a space to replace the air removed by exhaust fans
and/or combustion appliances.
Manometer - An instrument that measures air pressure.
Membrane - In the context of this guide, a membrane is a flexible material resistant
to air passage, such as a plastic film, that is laid over an earthen or gravel floor
(e.g., of a crawlspace) as part of a sub-membrane depressurization system.
Microbiological - In the field of IAQ, microbiological are living things so small that
individuals can only be seen through a microscope (e.g., algae, fungi, bacteria,
viruses).
Micromanometer - An extremely sensitive instrument for measuring air pressure,
capable of measuring air pressure differences as small as one thousandth of'
an inch W. C. (water column).
Mining - In this guide, mining refers to a phenomenon in which the arrangement
of the ventilation system inadvertently draws soil gas into a building.
Mitigation - Treatment or correction of a problem.
Negative pressure - Room A is under negative pressure relative to Room B if the air
pressure in Room A is lower than the air pressure in Room B.
Neutral pressure - Room A is under neutral pressure relative to Room B if the air
pressure in Room A is the same as the air pressure in Room B.
Outdoor air intake - An opening in the building exterior that is a planned entry
point for outdoor air.
Pascal - A unit of air pressure measuring .004 inches of water column.
A-5
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Glossary and Acronyms
Passive vent - An opening in the building exterior that is a planned exit point for
exfiltration air.
Permeability - The ability of soil gas to move through pores and cracks in the fill,
soil, and rock beneath the slab.
Permeable - Porous, allowing the passage of air.
Picocuries - A unit of measurement used to describe the radon concentration. A
curie is title amount of any radionuclide that undergoes exactly 3.7 x IQio
radioactive disintegrations per second. A picocurie is one trillionth (10-12) of
a curie, or 0.037 disintegrations per second.
Pitot tube traverse - A measurement strategy involving the measurement of air
pressures in the cross section of a duct.
Plenum - The term plenum is used to describe a) portions of the air distribution
system that make use of the building structure (e.g., the space above a
dropped ceiling is often used as a return plenum) and b) the sheet metal that
connects distribution ductwork to an air handling unit.
Positive pressure - Room A is under positive pressure relative to Room B if the air
pressure in Room A is higher than the air pressure in Room B.
Pre-mitigation radon concentration - The radon concentration before corrective
action; either 1) the averaged result of two short-term tests, or 2) the result of
a long-term follow-up test.
Pressure differentials - The difference between air pressures measured at two
locations.
Pressure field - A negative pressure field is an area that is maintained at a relatively
lower air pressure than an adjoining location.
Pressure field extension (PEE) - The extent to which the sub-slab area is
depressurized by the suction applied at a suction point, as evidenced by the
distance that a pressure change is induced in the sub-slab area.
Pressure sensor - In an ASD system, a device used to assess whether the ASD system
is maintaining the desired air pressure difference between the building
interior and the subslab.
A-6
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Glossary and Acronyms
Pressurization - Radon mitigation strategy based on adjusting ventilation until the
air pressure inside the building is consistently higher than the air pressure
than the area below the slab.
Radioactive decay - See decay.
Quality Assurance - A complete program designed to produce results which are
valid, scientifically defensible, and of known precision, bias, and accuracy.
Quality Control - Measurements made to ensure and monitor data quality.
Radon - A radioactive gas produced by the decay of radium.
Radon daughters - See radon decay products.
Radon decay products - The four radioactive elements that immediately follow
radon-222 in the decay chain. These elements are polonium-218, lead-214,
bismuth-214, and polonium-214. These elements have such short half-lives
that they exist only in the presence of radon.
Radon progeny - See radon decay products.
Return - Ventilation system components involved in the removal and recirculation
of ventilation air, as in return fan, return ducts, return grilles.
Run negative - Operate under negative pressure.
Run neutral - Operate under neutral pressure.
Run positive - Operate under positive pressure.
Schedule, mechanical equipment - Often shortened to schedule, refers to a table
listing items of mechanical equipment and describing the performance
characteristics required by the designer.
Setpoint - The value of the controlled condition at which a controlled device (e.g. a
freeze stat or fire damper) is set to operate.
Short-term (radon) testing - Radon tests that are between 2 and 90 days in duration.
A-7
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Glossary and Acronyms
Soil gas - The mixture of air, water vapor, and any natural or synthetic
contaminants found in the spaces between soil particles and the cracks in
rock.
Source strength - The concentration of radon in the soil or bedrock underlying the
building.
Stack effect - The overall upward movement of air inside a building that results
from heated air rising and escaping through openings in the building
envelope, thus causing indoor air pressure in the lower portions of a building
to be lower than the pressure in the soil beneath or surrounding the building
foundation.
Stratification - Arrangement in layers. In this guide, stratification is used to describe
the fact that layers of colder air tend to underlie layers of warmer air.
Sub-membrane depressurization - ASD beneath an installed membrane.
Substructure - The building foundation.
Suction pit - Part of an ASD system; a pit created by removing subslab aggregate
below a suction point.
Suction point - Part of an ASD system; the location at which ASD ductwork
penetrates the building slab (or an installed membrane).
Supply - Ventilation system components involved in providing ventilation air, as
in supply fan, supply ducts, supply diffusers.
Tensiometer - A device that measures a damper's position.
Test and balance (TAB) - A term used in the HVAC industry, referring to the
testing, adjusting, and balancing of the HVAC system so that airflows
conform to design specifications.
Tightness - In the context of building construction, the ease with which air leaks
through cracks and openings in the building shell.
Transom - A manually-controlled opening above a door used to allow air to exit a
room.
Underventilation - In this guide, refers to inadequate supply of outdoor air.
A-8
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Glossary and Acronyms
Unit ventilator - A fan-coil unit package device for applications in which the use of
outdoor air and return air mixing is intended to satisfy tempering
requirements and ventilation needs.
Uranium - The radioactive element that decays, through a series of steps, into
radium, radon, radon progeny, and, finally, into lead.
Vacuum test - The vacuum test of pressure field extension is a diagnostic test used
to evaluate the potential success of mitigation using ASD.
Ventilation - Process of supplying or removing air by natural or mechanical means
to or from any space; such air may or may not have been conditioned.
Ventilation zone - In this guide, the room or rooms provided with ventilation air
by a particular unit of ventilation equipment.
Working floorplan - In this guide, a small floorplan such as a fire escape floorplan,
used for recording notes and observations.
Acronyms
AABC - Associated Air Balance Council
ACM - asbestos-containing material
AHU - air handling unit
ASHRAE - American Society of Heating, Refrigerating, and Air-Conditioning
Engineers, Inc.
AHERA - Asbestos Hazard Emergency Response Act
ASD - active soil depressurization
CFM (or cfm) - cubic feet per minute
CC*2 - carbon dioxide
CRM - continuous radon monitor
A-9
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Glossary and Acronyms
EPA - (U.S.) Environmental Protection Agency
HEPA - high efficiency participate air (filter)
HVAC - heating, ventilation, and air conditioning
LAQ - indoor air quality
MA - make-up air
NEBB - National Environmental Balancing Bureau
NFPA - National Fire Protection Association
NSC - National Safety Council
NIOSH - (U.S.) National Institute for Occupational Safety and Health
OA - outdoor air
ORD - (U.S. EPA) Office of Research and Development
ORIA - (U.S. EPA) Office of Radiation and Indoor Air
pCi/L - picocuries per liter
PFE - pressure field extension
PM - preventive maintenance
ppm - parts per million
PVC - polyvinyl chloride
RA - return air
RCP - (U.S. EPA) Radon Contractor Proficiency program
RMP - (U.S. EPA) Radon Measurement Proficiency program
RRTC - (U.S.) Regional Radon Training Center
A-10
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Glossary and Acronyms
SA - supply air
SEP - (U.S. EPA) School Evaluation Program
SMACNA - Sheet Metal and Air Conditioning Contractors' National Association
Inc. '
TAB - testing, adjusting, and balancing (of HVAC systems)
UV - unit ventilator
W.C. - water column
A-ll
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Resources
Appendix B: Resources
REFERENCES
Contact your State or Regional EPA offices to obtain these documents:
1. Radon Measurement in Schools - Revised Edition, EPA 402-R-92-014.
2. Radon Prevention in the Design and Construction of Schools and Other Lame
Buildings, EPA 625-R-92-016.
3. Radon Mitigation Standards, EPA 402-R-93-078.
4. Building Air Quality, EPA 400-1-91-033.
REGIONAL RADON TRAINING CENTERS
EPA's four Regional Radon Training Centers (RRTCs) provide a range of training in
radon measurement and mitigation to the public. Contact the training centers
directly for information on course offerings, schedules, and fees.
Eastern Regional Radon Training
Center
Rutgers University
Radiation Science
Kilmer Campus, Building 4087
New Brunswick, NJ 08903
(908) 932-2582
Mid-West Universities Radon
Consortium
University of Minnesota
1985 Buford Avenue (240)
St. Paul, MN 55108-6136
(612) 624-8747
Western Regional Radon Training
Center
Department of Industrial Sciences
Colorado State University
Fort Collins, CO 80523
(800) 462-74597(303) 491-7801
Southern Regional Radon Training
Center
Auburn University
Department of Civil Engineering
238 Harbert
Auburn University, AL 36849-5337
(800) 626-27037(205) 844-6271
B-l
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Resources
EPA REGIONAL OFFICES
Region 1: CT, MA, ME, NH, RL VT
Radiation Program Manager
U.S. Environmental Protection Agency
John F. Kennedy Federal Building
Room 2311
Boston, MA 02203
(617) 565-4502
Region 2: NJ, NY (also Guam, Virgin
Islands, Puerto Rico)
Chief, Radiation Branch (AWM-RAD)
U.S. Environmental Protection Agency
Federal Plaza, Room 1005A
New York, NY 10278
(212) 264-4110
RegionS: DE, MD, PA, VA, WV
Radiation Program Manager
Special Program Section (3AT12)
U.S. Environmental Protection Agency
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-8326
Region 4: AL, FL, GA, KY, MS, NC, SC,
TN
Radiation Program Manager
U.S. Environmental Protection Agency
345 Courtland Street, N.E.
Atlanta, GA 30365
(404) 347-3907
Region 5: IL, IN, MI, MN, OH, WI
Radiation Program Manager
(AT-185)
U.S. Environmental Protection Agency
77 West Jackson Boulevard,
Chicago, IL 60604-3507
(312) 886-6175
Region 6: AR, LA, OK, NM, TX
Radiation Program Manager
U.S. Environmental Protection Agency
Chief, Technical Section (6T-ET)
Air, Pesticides, and Toxics Division
1445 Ross Avenue
Dallas, TX 75202-2733
(214) 655-7224
Region?: IA,KS,MO,NE
Radiation Program Manager
U.S. Environmental Protection Agency
726 Minnesota Avenue
Kansas City, KS 66101
(913) 551-7605
Region 8: CO, MT, ND, SD, UT, WY
Radiation Program Manager
(8HWM-RP)
U.S. Environmental Protection Agency
999 18th Street, Suite 500
Denver, CO 80202-2405
(303) 293-1440
Region 9: AZ, CA, HI, NV
Radiation Program Manager
(Al-1)
U.S. Environmental Protection Agency
75 Hawthorne Street
San Francisco, CA 94105
(415) 744-1048
Region 10: AK,ID,OR,WA
Radiation Program Manager
(AT-082)
U.S. Environmental Protection Agency
1200 Sixth Avenue
Seattle, WA 98101
(206) 553-7660
B-2
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Resources
STATE RADON CONTACTS
Alabama
800-582-1866
205-242-5315
Alaska
800-478-8324
907-465-3019
Arizona
602-255-4845
Arkansas
501-661-2301
California
800-745-7236
916-324-2208
Colorado
800-846-3986
303-692-3057
Connecticut
203-566-3122
T~X 1
Delaware
800-554-4636
302-739-3028
District of
Columbia
202-727-5728
Florida
800-543-8279
904-488-1525
Georgia
800-745-0037
404-657-6534
Hawaii
808-586-4700
Idaho
800-445-8647
208-334-6584
Illinois
800-325-1245
217-786-7127
Indiana
800-272-9723
317-633-0150
Iowa
800-383-5992
515-242-5992
Kansas
913-296-6183
Kentucky
502-564-3700
Louisiana
800-256-2494
504-925-7042
Maine
800-232-0842
207-287-5676
Maryland
800-872-3666
410-631-3301
Massachusetts
general info:
617-727-6214
technical info:
413-586-7525
Michigan
800-723-6642
517-335-8037
517-335-8190
Minnesota
800-798-9050
612-627-5012
Mississippi
800-626-7739
601-354-6657
Missouri
800-669-7236
314-751-6083
Montana
406-444-3671
Nebraska
800-334-9491
402-471-2168
Nevada
702-687-5394
New
Hampshire
800-852-3345
x4674
603-271-4674
New Jersey
800-648-0394
609-987-6396
New Mexico
505-827-4300
New York
800-458-1158
518-458-6451
North
Carolina
919-571-4141
North Dakota
701-221-5188
Ohio
800-523-4439
614-644-2727
Oklahoma
405-271-8118
Oregon
503-731-4014
Pennsylvania
800-237-2366
717-783-3594
717-783-3595
Rhode Island
401-277-2438 '
South
Carolina
800-768-0362
South Dakota
800-438-3367
605-773-6035
Tennessee
800-232-1139
615-532-0733
Texas
512-834-6688
Utah
800-458-0145
801-536-4250
Vermont
800-640-0601
802-865-7730
Virginia
800-468-0138
804-786-5932
Washington
800-323-9727
206-753-4518
West Virginia
800-922-1255
304-558-3526
Wisconsin
698-267-4795
Wyoming
800-458-5847
307-777-6015
Guam
617-646-8863
Puerto Rico
809-767-3563
Virgin Islands
800-468-0138
B-3
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Resources
BIBLIOGRAPHY
1. American Association of School
Administrators, Schoolhouse in the Red,
Arlington, VA, 1992.
2. American Society of Heating, Refrigeration,
and Air-Conditioning Engineers, ASHRAE
Standard 62-1989: Ventilation for Acceptable
Indoor Air Quality, American Society of
Heating, Refrigerating and Air-Conditioning
Engineers, Inc., Atlanta, 1989.
3. American Society of Testing and Materials
(ASTM E779), "Standard Test Method for
Determining Air Leakage Rate by Fan
Pressurization," 1987.
4. Brennan, T., M. Clarkin, W. Turner, G. Fisher,
R. Thompson, "School Buildings With Air
Exchange Rates That Do Not Meet Minimum
Professional Guidelines or Codes and
Implications for Radon Control," Proceedings
of the 1991 ASHRAE Indoor Air Quality,
Healthy Buildings Conference.
5. Brennan, T., G. Fisher, R. Thompson, W. A.
Turner, "Extended Heating, Ventilation, and
Air Conditioning Diagnostics in Schools in
Maine," Proceedings of the 1991 International
Symposium on Radon and Radon Reduction
Technology, Philadelphia, PA.
6. Brennan, T., G. Fisher, B. Ligman, W. Turner,
R. Thompson, "Fan Pressurization of School
Buildings," presented at Building Thermal
Envelope V. Conference 1992, Clearwater
Beach, FL.
7. Craig, A.B., K.W. Leovic, and D.B. Harris,
"Design of Radon Resistant and Easy-to-
Mitigate New School Buildings," presented
at the 1991 International Symposium on
Radon and Radon Reduction Technology,
Philadelphia, PA, April 1991.
8. Fisher, G., R. Thompson, T. Brennan, W.
Turner, "Diagnostic Evaluations of Twenty-
six U.S. Schools - EPA's School Evaluation
Program," Proceedings of the 1991
International Symposium on Radon and
Radon Reduction Technology, Philadelphia,
PA, EPA.
9. Fisher, G., B. Ligman, T. Brennan, R,
Shaughnessy, B. Turn, B. Snead, "Radon
Mitigation in Schools Utilizing Heating,
Ventilation and Air-Conditioning Systems,"
Proceedings of the 1993 International
Workshop on Indoor Radon Remedial Action,
Rimini, Italy.
10. Leovic, K.W., A.B. Craig, D.W. Saum,
"Radon Mitigation in Schools," ASHRAE
Journal, Vol. 32, No. 2, February 1990.
11. Leovic, K.W., "Summary of EPA's Radon
Reduction Research in Schools During 1989-
90," U.S. EPA, Office of Research and
Development, EPA-600/8-90-072 (NTIS
PB91-102038), October 1990.
12. Leovic, K.W., A.B. Craig, and D.B. Harris,
"Update on Radon Mitigation Research in
Schools," EPA-600/D-91-229 (NTIS PB91-
242958), presented at the 1991 Annual AARST
National Fall Conference, Rockville, MD,
October 1991.
13. Leovic, D.W., A.B. Craig, and D.B. Harris,
"Radon Prevention in the Design and
Construction of Schools and Other Large
Buildings," Architecture/Research, Vol. 1,
No. 1, pp 32-33, October 1991.
14. Leovic, K.W., H.E. Rector, and N.L. Nagda,
"Costs of Radon Diagnostics and Mitigation
in School Buildings," presented at the 85th
Annual Meeting and Exhibition of the Air
and Waste Management Association, Kansas
City, MO, June 21-26,1992.
B-4
-------
Resources
15. Leovic, K.W., H. Rector, and N. Nagda,
"Costs of Radon Diagnostics and Mitigation
in School Buildings/' presented at the 85th
Annual AWMA Conference, Kansas City,
MO, June 1992.
16. Parker, J.D, "HVAC Systems in the Current
Stock of U.S. K-12 Schools," EPA-600/R-92-
125 (NTIS PB 92-218338), July 1992.
17. Persily, A. Manual for Ventilation
Assessment in Commercial Buildings, U.S.
Department of Commerce, NIST, Building
and Fire Research Laboratory, Gaithersburg,
MD, January 1994.
18. Phillips, J., L. Ratcliff, J. Bergsten, "Results
of the National School Radon Survey,"
Proceedings of the 1992 International
Symposium on Radon and Radon Reduction
Technology, Minneapolis, MN, EPA.
19. Pyle, B.E. and K.W. Leovic, "A Comparison
of Radon Mitigation Options for Crawl Space
School Buildings," Presented at the 1991
Symposium on Radon and Radon Reduction
Technology, Philadelphia, PA, April 1991.
20. Shaughnessy, R., T. Brennan, E. Levetin, B.
Ligman, et. al. "Trenton Elementary School,
School Evaluation program Report," Office of
Radiation and Indoor Air, U.S. EPA, 1993.
21. Shaughnessy, R.J., B.H. Turk, E. Levetin, T.
Brennan, G. Fisher, and B.K. Ligman, "Impact
of Ventilation/Pressurization on Indoor Air
Contaminants in Schools," draft report
submitted to U.S. EPA, Office of Radiation
and Indoor Air, Washington, DC, 1993.
22. Thompson, R., G. Fisher, T. Brennan, W.A.
Turner, "HVAC Retrofit for Healthy
Schools," Proceedings of the ASHRAE
Health Building Conference - IAQ '91,
Washington, DC.
23. Turk, B.H., G. Powell, G. Fisher et. al.,
"Multi-Pollutant Mitigation by
Manipulation of Crawlspace Pressure
Differentials," Proceedings of the 1992
International Symposium on Radon and
Radon Reduction Technology, U.S. EPA,
Research Triangle Park, NC, 1992.
24. Turk, B.H., G. Powell, G. Fisher, B.Ligman,
et. al., "Improving General Indoor Air
Quality While Controlling Specific
Pollutants in Schools," Proceedings of the
1993 International Conference on Indoor Air
Quality and Climate, Helsinki, Finland.
25. U.S. Environmental Protection Agency, U.S.
Department of Health and Human Services,
and U.S. Public Health Service, A Citizen's
Guide to Radon (Second Edition), May 1992.
26. U.S. Environmental Protection Agency, Radon
Measurement in Schools - Revised Edition,
Office of Radiation and Indoor Air, U.S. EPA.
EPA-402-R-92-014, July 1993.
27. U.S. Environmental Protection Agency,
Radon Mitigation Standards, Office of
Radiation and Indoor Air, EPA-402-R-93-078,
October, 1993.
B-5
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1
Metric Conversion Factors
Appendix C: Metric Conversion Factors
Although it is EPA policy to use metric units in its documents, non-metric units
have been used in this report to be consistent with common practice in the radon
mitigation field. Readers may refer to the following conversion factors as needed
Non-Metric Times
cubic foot (ft3) 28.3
cubic foot per minute (fts/min) 0.47
foot (ft) 0.305
gallon (gal.) 3.79
horsepower (hp) 745
inch (in.) 2.54
inch of water column (in. WC) 248.9
mil (0.001 in) 25.4
picocurie per liter (pCi/L) 37
pound per square inch (psi) 6894.8
square foot (ft2) 0.093
Yields Metric
liters (L)
liters per second (L/s)
meter (m)
liters (L)
watts (W)
centimeters (cm)
pascals (Pa)
micrometers (|im)
becquerels per cubic meter
pascals (Pa)
square meter (m2)
C-l
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Mitigation Cost Information
Appendix D: Mitigation Cost Information
It is difficult to provide general estimates of radon mitigation costs due to parameters that
vary from school to school. Parameters such as building size, type of ventilation system, extent
of the radon problem, and building construction all influence the cost of radon diagnostics and
mitigation. However, in an attempt to provide some guidance to school districts who need to
estimate these costs in planning their radon program, the following discussion is provided with
the caution that this information be used with discretion. The cost estimates presented below do
not include operation and maintenance costs.
EPA has obtained mitigation cost data by: 1) surveying mitigators and 2) performing
mitigation demonstrations in school buildings.
The survey consisted of a questionnaire that was developed by EPA's Office of Research
and Development and sent to nine radon mitigators with experience in school buildings. This
survey described two typical school buildings of different sizes and were identified as requiring
an Active Soil Depressurization (ASD) system. Building 1 was described as requiring two
suction points and Building 2 requiring 10 suction points. The respondents were asked to
estimate costs for 5 work elements associated with radon diagnostics and mitigation. Seven of
the nine mitigators responded with complete cost information. The final analysis is summarized
below in Table 1.
Work Element
1) Review Building
Plans
2) ASD Diagnostics
3) ASD System Design
4) ASD Material Costs
5) ASD System
Installation &
Checkout
Totals*
Cost per ft2
Cost per suction point
Building 1 (20,000 ft2)
Average Cost
$265.00
$1,337.00
$925.00
$3,231.00
$4,466.00 (for 2 suction
points)
$10,068.00
$0.50
$5,034.00
Building 2 (50,000 ft2)
Average Cost
$454.00
$3,088.00
$1,254.00
$9,453.00
$12,150.00 (for 10 suction
points)
$26,334.00
$0.53
$2,633.00
* - Totals were computed using the average totals for each mitigator rather than each work
element.
TABLE 1: AVERAGE MITIGATION & DIAGNOSTIC COSTS FOR ASD FROM SURVEY
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Mitigation Cost Information
The results of the survey provide an estimate of the cost factors for ASD diagnostics and
mitigation in schools. Based upon the survey results, it is estimated that an average cost for ASD
diagnostics and installation hi a typical school would be $0.50 per ft2. About 20% of this estimate
would be devoted to the diagnostics and the remaining 80% to the installation. These costs would
be higher in schools with extensive subslab walls, poor pressure field extension, and extensive
building code and/or asbestos complications. Costs would be lower in schools with good
pressure field extension and no subslab barriers.
In addition to the survey, EPA has demonstrated radon mitigation in several schools
using local contractors and local design professionals to design and install ventilation systems, as
well as install ASD systems. Based on these experiences, ventilation costs could range from no
installation cost, such as when minor adjustments are the only requirement to an existing system,
to the installation of an entire mechanical ventilation system which varies in cost depending
upon the size of the system. The costs experienced by EPA are summarized below according to
site. A brief description of the mitigation system and the costs associated with the system are
presented. These costs are likely to be higher than would actually be experienced by school
districts due to the expedited construction schedules of several of the projects. Costs reflect
hardware, engineering fees, and installation costs.
Site 1: HVAC system controls were restored and modified to increase outdoor air as
originally designed.
Building Area: 19,200ft2
Cost of Project: $17,700
Costs per Square Foot: $0.92/ft2
Site 2: HVAC system controls were restored and modified to increase outdoor air as
originally designed.
Building Area: 25,700 ft2
Cost of Project: $10,340
Cost per Square Foot: $0.40/ft2
Site 3: Complete ventilation system was installed in two buildings. The first building's
system consisted of a heat recovery ventilator that exhausts air from a crawl
space, resulting in depressurization, and provides outdoor ventilation to the
classrooms. The second building's system consisted of a roof top ventilation
system that provides outdoor air to the classrooms which pressurizes the occupied
space to prevent radon entry. Extensive hydronic (installation of hot water heating
coils and piping) work was also performed to condition outdoor air to maintain a
comfortable classroom temperature. The building's previous condition provided
no mechanical outdoor air ventilation.
D-2
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Site 4:
Site 5:
Site 6:
Mitigation Cost Information
Total Buildings Area: 11,690 ft2
Cost of Project: $120,700
Cost per Square Foot: $10.33/ft2
Active subslab depressurization system was installed. School was classified as
difficult to mitigate due to the poor pressure field extension. High pressure suction
fans were installed as part of the system.
Building Area: 13,600ft2
Cost of Project: $11,600
Cost per Square foot: $0.85/ft2
A combination mitigation approach was used. Active subslab depressurization
system was installed. The entire HVAC system was also replaced due to poor
indoor air quality (i.e. high indoor CO2 concentrations, mold and mildew growth).
A new ventilation system was installed to provide outdoor air to the classrooms.
This system was designed to maintain acceptable relative humidity levels in the
building despite the introduction of a large quantity of high relative humidity
outdoor air.
Building Area: 13,240 ft2
Active Subslab Depressurization System
Cost of Project: $12,140
Cost per Square Foot: $0.92/ft2
HVAC System
Cost of Project: $104,990
Cost per Square Foot: $7.93/ft2
A combination mitigation approach was used. An innovative tunnel
depressurization system was installed with a variable frequency drive which
changes the fan speed to maintain a constant depressurization and to reduce
energy consumption. The HVAC system was also restored to provide outdoor air
to the classrooms.
Building Area: 50,000 ft2
Tunnel Depressurization System
Cost of Project: $21,100
Cost per Square Foot: $0.42/ft2
D-3
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Mitigation Cost Information
HVAC System Restoration
Cost of Project: $18,900
Cost per Square Foot: SO.SS/ft2
This information provides actual cost data resulting from 6 school radon mitigation
installations. Costs vary depending on the existing HVAC equipment (i.e. condition of the
system and it's capabilities) and what other equipment needs may be required. ASD cost are
higher than the survey data due to the increased number of suction points required to extend a
negative pressure field in the compact, low permeability material found beneath the concrete
slabs.
D-4
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Case Studies
Appendix E: Case Studies
Case Study 1
I. INTRODUCTION
This case study is an example of a school that was successfully mitigated by implementing
two mitigation strategies. By installing an ASD system and replacing the HVAC system the radon
concentrations are maintained below EPA's action level of 4 pCi/1. The project was expected to be
difficult due to the condition of the existing HVAC system and the fine grained material under the
slab. This project also provided the opportunity to address the concerns of meeting the outdoor
ventilation rate of 15 cfrn/person in a school classroom, as recommended in the ASHRAE standard
62-1989 "Ventilation for Acceptable Indoor Air Quality", in a high relative humidity climate as
found in the state of Florida. The completed project provides the occupants of this school with
recommended outdoor air rates and radon concentrations below 4 pCi/1.
II. SCHOOL DESCRIPTION
The school is an elementary school built in 1968 located in the state of Florida. The building
is single story, masonry block construction, with a floor area of approximately 13,240 ft2. It is
shaped like a "figure eight" with 5 classrooms in each of the "loops" of the eight (see school's floor
plan). The roof is a built up flat roof that supports the roof-top HVAC equipment.
III. INITIAL INVESTIGATION
The initial investigation was performed by several "team members" including the following:
EPA listed radon proficient mitigation contractors, a mechanical engineer and a school facility
operator. The combined expertise was essential in determining the most appropriate mitigation
strategies for this building.
Pre-mitigation Radon Measurements
The pre-mitigation radon measurement data consisted of initial measurement results as well
as the follow up measurement results. The initial measurements were performed using charcoal
canisters over a 48 hour period. The follow up measurementsjwere performed, in accordance with
Florida radon measurement protocols, using electret ion chambers that were opened during occupied
times and closed during unoccupied times. Two sets of follow up measurements were performed for
a period of 11 to 13 days; the first set was taken in September and the second set was taken in
January. The initial measurement results ranged from 2 pCi/1 to 20 pCi/1 with the average being 12
pCi/1. The raw data from the initial measurements were not available for tabulation. The follow-up
measurement results are reproduced in Table 1.
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Case Studies
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E-2
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Case Studies
Room
#
1
2
3
4
5
6
7
10
11
12
13
14
15
18
19
20
21
23
23c
Follow-up Measurement
Results 09/23/91 to 10/04/91
(occupied hrs. only)
7.0
9.2
10.0
8.1
6.7
6.8
8.8
8.9
8.6
8.6
8.1
7.8
8.3
5.1
6.6
8.0
6.7
1.8
8.0
Follow-up Measurement
Results 01/21/92 to 02/03/92
(occupied hrs. only)
21.8
21.8
36.6
37.1
30.3
36.6
34.1
28.7
31.0
30.1
15.1
22.9
17.2
14.9
13.7
11.7
16.3
4.7
24.6
Follow-up Measurement
Average
14.4
15.5
23.3
22.6
18.3
21.6
21.5
18.8
19.8
19.4
11.6
15.4
12.8
10.0
10.2
9.9
11.5
3.3
163
1 ABLb 1: follow-up Radon Measurement Results
Building Plan Review
The only building plans available were a site plan, floor plan, architectural elevation plan
and one sheet of the plumbing plans. Mechanical or foundation plans were not available. A review
of the floor plan revealed that the school was designed for 8 classrooms and 2 multi-purpose rooms
located in the center areas of the "loops" of the figure eight. The plumbing plan provided
information on possible entry points around plumbing penetrations. Each of the 8 classrooms had
two rest rooms with pipe penetrations through the slab.
Walk Through Inspection
Observations during the walk through included: excessive biological (mold & mildew)
growth on carpeting and walls in several classrooms. The multipurpose rooms were being used as
classrooms, contrary to the rooms' original designed use. The roof appeared to leak in several
locations. Each of the exterior classrooms had 1 operable window that was designated as an
emergency exit. A 1% inch hole was drilled through the slab to visually inspect the subslab material.
The material was a sand/dirt composition that was tightly compacted.
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Case Studies
HVAC Evaluation
The HVAC system consisted of rooftop package traits with electric strip heating. Each of the
exterior classrooms was equipped with a thermostat that controlled 1 of the 8 rooftop package units,
i.e. one unit for each of the exterior classrooms. The multipurpose rooms, located in the center of
the "loops" of the figure eight, was heated and cooled by each of the 4 classrooms surrounding it,
i.e. a portion of air from each of the 4 rooftop package units supplied air to each of the
multipurpose rooms. The rooftop package units were original equipment dating back to 1968. The
units were rusted beyond repair and were noisy. The interior of the units were reservoirs of
biological growth with visible growth in the drain pans and on the insulated panels of the unit.
Outdoor air intake capabilities consisted of a small (4" by 4") hole in the return air duct of each unit
that was located beneath a shroud which covered the roof penetration of the ductwork. Using
chemical smoke, it was determined that outdoor air was not entering through the intakes into the
rooftop units due to the small size of the opening and the condition of the filter that was placed in
the opening. The building was equipped with 9 rooftop exhaust fans of which 1 was operational.
Initial Investigation Conclusions
After the initial investigation was complete, the team concluded that the HVAC system, as a
stand alone strategy, would not be capable of reducing the radon concentrations below 4 pCi/1 due
to the high levels originally measured. However, due to the deteriorated equipment and the lack of
outdoor ventilation the team concluded that the mitigation strategy must deal with the HVAC
system. Because of the HVAC system's age and condition, it was determined that the system was
beyond restoration and any effort to restore the system would be futile. The initial radon
concentrations exceeded 10 pCi/1 indicating that detailed diagnostics needed to be performed to
determine whether ASD could be used as part of the mitigation strategy. Therefore, a final decision
of what to do with the existing HVAC system would be made upon completion of the detailed
investigation.
IV. DETAILED INVESTIGATION
Walk Through Inspection
The walk through involved an inspection of the building shell and performing a blower door
test to determine the "tightness" of the building. The leakage area of the building was so large that
accurate test results could not be obtained. Visually inspecting the building shell for obvious "leaks"
revealed large openings to the outside where the HVAC ductwork penetrated through the roof. The
rest of the building shell appeared relatively "tight." The large openings would have to be sealed and
a repeat blower door test performed in order to determine whether building pressurization would be
an effective radon control strategy.
Subslab Vacuum Test
The detailed diagnostics involved performing a subslab vacuum test to determine the
pressure field extension for the sand/dirt material under the slab. As expected, the pressure field
E-4
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Case Studies
extension was quite poor with an extension of 12 feet at .002 inches w.c. pressure differential and an
air volume of 17 cfin. With such poor communication through the subslab material, a high pressure
ASD system would have to be used with multiple suction points in order to cover the entire slab
area. The effect of the ventilation system on the pressure field extension was taken into
consideration while the vacuum test was being performed. Under normal operating conditions, the
HVAC system would not inhibit the pressure field extension obtained during the test.
V. THE MITIGATION SYSTEM
With all the data collected from the initial and detailed investigation, the team concluded
that the mitigation strategy would consist of the following:
1. Install an ASD system.
2. Replace the existing 9 rooftop package HVAC units.
3. Replace the existing 8 exhaust fans that were non-operational.
The strategy incorporated an ASD and HVAC approach due to the high radon
concentrations and poor subslab pressure field extension. This combined approach controls radon by
reversing the flow of soil gas via the ASD system and dilutes the radon that may inadvertently enter
due to the poor soil communication via the HVAC system.
Final Mitigation
ASD SYSTEM: The ASD system consisted of 3 centrifugal high suction fans and 18 slab
penetrations where suction was applied. Each of the ASD system's piping was routed above the drop
ceiling and exits through the roof to an in-line centrifugal fan. The operating conditions of each
system are shown in Table 2.
SYSTEMS
1
2
3
Pressure Diff. @ Slab
penetrations Cinches we)
1.4
3.2
2.5
Total Air Volume of
system fcfm)
64
17
51
1 ABLb 2: ASD system performance
HVAC SYSTEM: The HVAC system consisted of replacing the existing nine (9) rooftop package
units and the installation of two (2) new 100% outdoor air units. The outdoor air units were
designed to introduce 15 cfm/person in each of the 10 classrooms. It was necessary to install this
"separate" outdoor air system in order to remove moisture from the outdoor air before it is
introduced into the classrooms. These units are designed to remove the moisture required to
maintain relative humidity levels in the classrooms that are acceptable for occupant comfort and
inhibit biological growth, i.e. mold, mildew, etc. The 8 exhaust fans were also replaced with new
E-5
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Case Studies
equipment. The increased air volume being exhausted, resulting from the replaced exhaust fans, did
not affect the effectiveness of the ASD system. The total air being exhausted from the classrooms is
less than the total outdoor air being supplied, therefore maintaining positive pressure in the
classrooms relative to the subslab..
Post Mitigation Radon Testing
Continuous radon monitors were used to measure the radon concentrations in classrooms 19,
21 and 5. These rooms were chosen because of their central location and initial radon
concentrations. The results of the continuous radon measurements provide information on the effect
the HVAC operation has on radon concentrations. Figure 1 is a graph of the radon concentration
results in classroom 19 over a period of one week during the month of May 1993 with the ASD
system operating during the entire test period. The outdoor air unit operation was also monitored for
on/off status only. It is clearly evident that the ASD system has reduced the radon concentration
when compared to the initial measurement results. However, radon concentrations approached the 4
pCi/1 action level despite the continuous operation of the ASD system. The introduction of the
outdoor air combined with the ASD system maintains concentrations, during the building's occupied
times, well below 4 pCi/1. This positively confirms the "team's" conclusion to use a combined
ASDMVAC mitigation strategy for reducing radon concentrations in this school.
CONTINUOUS RADON CONCENTRATIONS & O.A. OPERATION
ROOM 19; 5/1 6/93 TO 5/23/93
Radon Concentration (pCi/L)
|fjj| OUTDOOR AIR UNIT ON
DATA BEGINS ON SUNDAY AND ENDS THE FOLLOWING SUNDAY; ASD SYSTEM ON DURING TEST PERIOD
FIGURE I : POST MITIGATION RADON MEASUREMENTS
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VI. COST INFORMATION
The costs for this project can be broken into 3 categories; 1) ASD system cost, 2) ventilation
system cost, and 3) engineering and testing, adjusting & balancing costs. This cost information is
shown below in Table 3. The costs shown below are likely to be higher than would actually be
experienced by school districts due to the expedited construction schedule for this demonstration
project.
ASD
HVAC
Engineering
Equipment
Cost
$37,273.00
Labor Cost
$12,140.00'
$48,251.00
$19,500.00
Cost/ft2
$0.92
$6.46
$1.47
1 Includes equipment costs
VII. CONCLUSIONS
This case study represents a combination approach to radon mitigation. The resulting
mitigation system is a good example of an integrated approach that reduces radon concentrations
and contributes to improving indoor air quality by introducing the recommended outdoor air rate of
15 elm/person. Radon concentrations have been monitored over a 12 month time period in
classrooms 19,21 and 5. These data indicate that the ASD system is maintaining radon
concentrations below 4 pCi/L most of the time. However the concentrations do peak above 4 pCi/L
when the HVAC system is shut down, such as during night time operation. The HVAC system
contributes to the control of radon by providing outdoor air to the building thereby diluting the
radon that has "eluded" the ASD system. The team's conclusion to use a combined approach was
well justified based on the monitoring data as well as the resulting carbon dioxide (CO2) data A
47 /o reduction in CO2 concentration was observed resulting from the increased outdoor air into the
classrooms. The average pre-mitigation CO2 concentration (obtained during periodic walk through
m all classrooms ) was 1672 parts per million (ppm) and the post-mitigation CO2 average was 880
ppm An integrated approach to radon mitigation in schools which controls radon as well as
contributes to improving indoor air quality, should be the goal of radon mitigation whenever
possible.
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Case Study 2
I. INTRODUCTION
This case study is an example of a school with moderately elevated radon levels (<10
pCi/L). At the time of the initial team investigation, there was virtually no outdoor air being
delivered to the classrooms via the school's ventilation system. The only outdoor air being
introduced into the building was through natural infiltration and the occasional use of operable
classroom windows. In addition, the school had subslab ductwork which has the potential to be a
significant source of radon entry and required a thorough investigation. This case study is an
example of a school that was mitigated by restoring the ventilation system, however this
mitigation strategy is not proving to be fully successful because of limitations in the ventilation
system's original design.
II. SCHOOL DESCRIPTION
The building is a single-story, slab-on-grade, masonry structure with a hexagonal layout
located in the State of New Mexico (see Figure 1). An open courtyard is located in the center of
the building. Individual, residential-type forced air furnaces provide heat and ventilation for each
classroom. The building is not equipped with air conditioning. Each classroom has operable
windows. The total floor area of the school is approximately 26,000 ft2, with 22 occupied rooms
(classrooms, offices, libraries, and lounges). The building was first occupied in 1968 and
currently includes kindergarten through 6th grade.
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SUPPLY
(TYPICAL)
Location of vacuum test hole
ฎ Lxjcation of field extension test holes
FIGURE 1: SCHOOL FLOOR PLAN
III. INITIAL INVESTIGATION
The initial investigation was performed by a team of people that included the following:
EPA listed radon proficient mitigation contractors, a mechanical engineer and a school facility
operator. The local mechanical contractor who was responsible for servicing the HVAC
equipment at the school was contacted and became a team member in evaluating the ventilation
system.
Pre-mitigation Radon Measurements
The pre-mitigation radon measurement data consisted of initial measurement results as
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well as follow-up measurement results performed by the State of New Mexico's Environment
Department, Radon Program. The initial measurements were performed using charcoal canisters
for a 72 hour period between March 1 and March 4, 1991. The follow-up measurements were
performed using Alpha Track Detectors (ATD) over a 4 month period between April 19 and
August 14,1991. Both the initial and follow-up measurements and their respective placement
locations are reproduced in Table 1.
Location
Library
Nurse
Principal's office
Room 1
Room 2
RoomS
Room 4
RoomS
Room 6
Room?
RoomS
Room 9
Room 10
Room 1 1
Room 12
Room 13
Room 14
Room 15
Room 16
Initial Radon Meas.
(CC 3/1- 3/4/9 l)pCi/L
4.4
4.0
6.7
4.5
5.9
4.6
4.2
5.4
5.8
4.6
5.0
5.2
3.7
4.5
4.6
4.7
5.4
5.6
4.0
Follow-up Radon Meas.
(ATD 4/19 - 8/14/91) pCi/L
2.7
3.7
2.0
5.0
4.2
4.7
4.7
5.3
3.5
1.6
3.4
3.5
0.9
2.9
4.3
5.3
2.9
4.2
CC - Charcoal Canister detector
ATD-Alpha Track detector
TABLE 1: INITIAL AND FOLLOW-UP RADON MEASUREMENT RESULTS
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The initial radon test results indicate that 18 of the 19 rooms tested during winter time
were at or above the EPA's guideline of 4 pCi/L. Follow-up radon test results indicate that 6 of
the 19 rooms had radon concentrations above 4 pCi/L. The warmer period in which the follow-up
measurements were performed may explain the lower radon concentrations due to decreased
stack effect and open windows (open windows were likely since the building does not have air
conditioning). The decision was made to evaluate the entire school due to the radon potential
that was observed in 18 of the 19 rooms initially measured.
Building Plan Review
A review of the building plans revealed valuable information on the construction
characteristics of the slab/foundation and the design/operational features of the ventilation
system. The foundation plans indicated a 4 inch slab with a waterproofing membrane directly
under the slab. The membrane was placed over 4 inches of gravel that was layered over
compacted earth. Foundation footings were located under the exterior perimeter walls and under
the interior corridor walls. There were no footings under the walls that separated the classrooms.
Individual, residential-type forced air furnaces provided heat and ventilation for each
classroom. There are 20 furnaces divided up into three mechanical rooms with a common
outdoor air and return air in each mechanical room. The quantity of outdoor air for each
classroom is controlled by dampers, and determined by the set points for temperature sensors
located in the air streams. Air is returned to the mechanical rooms via transfer grilles between
classrooms and corridor and from the corridor into the mechanical rooms. Ventilation is
distributed to the classrooms through supply ducts that are located below the concrete slab floor.
A pressure relief damper is located in the ceiling of each classroom. EPA has found the
combined configuration of subslab ductwork and residential HVAC equipment to be uncommon.
The plans also indicated that it might not be possible to deliver the ASHRAE guideline of
15 cubic feet per minute (cim) per occupant of outdoor air, due to existing equipment heating
capacity limitations.
Walk Through Inspection
Prior to the walk through, all radon measurements and notes from reviewing the building
plans were transferred onto a fire exit floor plan. Several key observations were made during the
walk through inspection of the building. The ventilation system was found to be operating with
the outdoor air dampers in the closed position. The building's 12 exhaust fans were inspected and
9 were found to be operational. The school facility person took note of the 3 fans that were
inoperable. Classroom supply vents, transfer grills, and relief dampers were also observed.
Despite the relatively low pre-mitigation radon levels, the team suspected that a
mitigation strategy based on ventilation alone may not be effective because of the existence of
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the subslab ductwork. Therefore, a 11A" hole was drilled through the slab in order to initially
assess the potential for an Active Soil Depressurization (ASD) system as well as to verify that the
material specified in the building plans was present. The subslab material beneath consisted of
W pebbles which corresponded with the building plans. Slab locations to conduct future vacuum
tests were also noted.
HVAC Evaluation
Upon further investigation of the ventilation system, it was discovered that the pneumatic
actuators for the outdoor air dampers were not responding to the control system's signals, i.e. to
open or close. The ventilation system's control diagrams were located and inspected to determine
the system's control sequence. It was determined that the system had been modified from the
original design control diagram. A closer examination of the outdoor air damper actuators
revealed that the pneumatic lines coming into the actuator had been soldered closed. This
explained why the actuators were not responding to the control system's signals to open the
dampers. Several of the actuators were found to be inoperable and needed to be repaired. In
addition, the control sequence had been changed to cycle the ventilation fans in response to the
thermostats located in each classroom. This caused the fans to operate only when the thermostat
called for heat. During the course of the day the fans would cycle on and off depending on the
heating requirement of the classrooms. On days when the temperature was moderate and outdoor
air could be used to cool the school, the control sequence prevented the fans from being
activated.
The relief dampers located in the classrooms were connected to the control system via
pneumatic lines. The relief dampers opened in conjunction with the outdoor air dampers to
provide pressure relief in the classroom for increased outdoor air ventilation when the outdoor
temperature is moderate.
The furnace air filters were the fiberglass panel type with an arrestance efficiency of 30%
and appeared to be relatively clean.
Because the team had individuals with air balancing expertise and the necessary
equipment, air flow measurements were performed on all the furnace units to determine total air
volume delivered to the classrooms. The results indicated that the air volume of several units
were not within acceptable tolerances (typically 10% of design air volume). The total air volume
of 11 units deviated from design by more than 10% (see Table 2).
Subslab ductwork was found to originate from each mechanical room and routed to the
classrooms. Radon has the potential to accumulate in subslab ductwork because ductwork is
inherently leaky and is in direct contact with the soil. When the ventilation system fan is not
operating radon can accumulate and be distributed into the building. When subslab ductwork is
used for supply air, radon can only accumulate in the ductwork when the ventilation fan is not
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operating. However, air leaks in the ductwork can allow supply air to increase the pressure of the
soil gas in the subslab material, perhaps enhancing radon entry through existing cracks and
openings in the slab. When the ductwork is used for return air, radon can accumulate when the
ventilation fan is off as well as "mine" radon when the fan is operating, i.e. duct is depressurized
and draws radon in.
Initial Investigation Conclusions
The results of the initial investigation indicated that restoration of the ventilation system
would be an appropriate mitigation strategy for two reasons 1) initial radon concentrations were
below 10 pCi/L, 2) outdoor air ventilation rates were extremely low given the fact that the
outdoor air dampers were found disabled. Given these results the team concluded that the
following ventilation related items would be implemented:
1. Unplug and reconnect the pneumatic control lines to the outdoor air damper
actuators.
2. Check and repair all broken damper actuators.
3. Disable the relief dampers in each classroom. The team concluded that disabling the relief
dampers would not inhibit the flow of air through the classrooms when the ventilation
system is supplying 100% outside air, due to the leakage area in the building envelope.
By disabling the dampers, the building's leakage area is reduced which helps to pressurize
the classrooms to reduce radon entry.
4. Make repairs and modifications to the ventilation system's controls so that the percentage
of outdoor air being introduced during occupied time is 25% to 30% of the total air
volume as specified in the original design. Because of the ventilation system's lack of
heating capacity, the recommended 15 cfm of outdoor air could not be met without
equipment replacement.
5. Test and balance the furnace units to restore the units' supply air volume to within 10% of
the design specifications.
6. Change and upgrade the furnace filters to a pleated type filter with a dust spot efficiency
of 30%. Even though the existing filters were clean, the upgraded filters remove smaller
airborne particles and have a longer life.
The team also concluded that a limited detailed investigation would be performed
because of the concern that radon could be accumulating in the subslab supply air ductwork
during the ventilation fan's off cycle. This situation could present a problem during morning
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start-ups because accumulated radon would be forced into the classrooms when the fan is turned
on.
Location
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
office
Design
Total Flow
(cftn)
1300
940
950
940
1100
950
940
1300
1300
950
940
940
950
940
1100
1300
1100
950
Before
Vent.
Restoration
Measured
Total Flow
(cfm)
750
960
720
870
760
990
880
690
1180
1190
1080
1390
920
1010
670
840
600
750
After Vent. Restoration
Measured Total
Flow (cfm)*
1200
960
830
870
1100
990
880
980
1200
980
1100
1200
920
1000
830
1300
1100
750
Estimated min.
outdoor air
(cfm/room)t
300
240
210
220
280
250
220
250
300
250
280
300
230
250
210
330
280
190
Estimated min. outdoor air
(cfm/person)**
10
8
7
7.3
9.2
8.3
7.3
8.3
10
8.3
9.3
10
7.7
8.3
7
11
9.3
19
* - After HVAC restoration was performed
f - Outdoor air estimated at minimum conditions (25%)
** - Number of occupants assumed to be 30 for all classrooms, 10 for the office
TABLE 2: VENTILATION SYSTEM SUPPLY AIR FLOWS
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IV. DETAILED INVESTIGATION
The detailed investigation consisted of performing a subslab vacuum test. This
diagnostic test was performed to assess the potential successfulness of an ASD system. The team
wanted to know whether an ASD strategy was a viable alternative strategy due to the uncertainty
in controlling radon resulting from the subslab ductwork.
Subslab Vacuum Test
The 11A" hole drilled during the initial investigation was used as the suction hole in
performing the vacuum test. Test holes were drilled at approximately 1 foot and 15 feet away
from the vacuum test hole (see Figure 1). Suction was drawn on the \1A" hole, using a vacuum
cleaner, while the pressure differential was measured at the test holes to determine the pressure
field extension (PFE) in the material beneath the slab. The PFE developed under the slab
extended to the farthest test hole when the vacuum was operated. At maximum vacuum
operating conditions the subslab region below the nearest test hole was depressurized 0.66 inches
water column (WC) (165 Pascals). The farthest test hole was depressurized 0.006 inches WC
(1.5 Pascals) while the flow through the vacuum was approximately 30 cfrn. To reach the
farthest test hole the pressure field extended past two subslab supply air ducts and two footings.
The layer of stone pebbles observed earlier is the main factor for the good PFE. As a result,
ASD could be a feasible radon control technique for this school building.
V. THE MITIGATION SYSTEM
The ventilation system was restored and all classroom's outdoor air ventilation rates were
increased. Table 2 illustrates the results of the test and balance that was performed on the furnace
units. Four units could not be balanced to within the 10% tolerance due to motor and pulley
limitations. The classroom outdoor air ventilation rates ranged from 7.0 to 11.0 cfrn/person after
the restoration had occurred. When compared to the estimated 1.0 cfrn/person which existed
before the mitigation efforts, a large improvement was made. The ventilation system's controls
were restored to provide outdoor air ventilation at all times during occupied hours.
Post Mitigation Radon Testing
With the ventilation system operating continuously during occupied times, post
mitigation measurements were performed over a 2 week period using Electret Ion Chambers.
Results of the measurements are shown in Table 3. The results indicate that all the rooms are
below the guideline of 4 pCi/L. The concentration of 3.9 pCi/L for classroom 15 may be due to
the supply air imbalance. This classroom's supply air is 24% lower than as designed. Proper air
volume could not be obtained due to the capacity of the fan's motor.
In order to establish the ventilation system's start-up and shut down times (to verify that
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the radon concentration is below 4 pCi/L whenever the classrooms are occupied), a continuous
radon monitor was placed in classroom 14. Figure 2 shows the averaged hourly radon
concentration taken over a 2 day period. The classrooms become occupied at 7:00 am and
unoccupied at 3:00 pm. The time clocks that control the ventilation system's mode of operation
was set for a 6:00 am start-up time and a 5:00 pm shut down time. The results of this
measurement indicate that radon is above 4 pCi/L for approximately 3 hours (7:00 am to 10:00
am) of the occupied time. It is speculated that this is due to the radon that has accumulated in the
subslab supply air ductwork during the unoccupied time (night setback mode) and is being forced
into the room when the system is started in the morning. To account for this, the time clocks
should be changed for a start-up time of approximately 2:00 am. This will give sufficient time for
the ventilation system to "purge" the supply air ductwork and dilute the radon in the classroom
so that the concentration is below 4 pCi/L when the classrooms become occupied. This case is an
extreme example of start-up time due to the radon that appears to be "pushed" into the
classrooms at the beginning of the ventilation start-up. The current shut-down time does not need
adjustment since radon does not exceed 4 pCi/L until approximately 10:00 pm when the school is
unoccupied.
Continuous Post Mit. Rn Measurements
Room 14
T | | i [ 1.1 I
00:00 04:0d ' 08:'00
02:00 06:00 1p:00 14:00
Time of Day
18:00 22:00
FIGURE 2: Continuous Post Mitigation Radon Measurements
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Location
Library
Music
Nurse
Principal's office
Room 1
Room 2
Room 3
Room 4
Room 5
Room 6
Room?
Room 8
Room 9
Room 10
Room 1 1
Room 12
Room 13
Room 14
Room 15
Room 16
Room 17
Post Mit. Radon Meas.
(EIC 4/5 -4/1 9/93) pCi/L
4.9*
2.3
2.7
1.5
1.8
2.5
2.4
1.7
2
2.2
2.1
1.7**
1.4
2.1
2.5
2.4
1.7
2.9
3.9
1.7
2.1
EIC - Electret Ion Chamber; concentration has been corrected for gamma background for New Mexico
* - Individual HVAC unit for Library was found operating under cycling condition vs continuous.
** - Found breaker for Room 8 furnace tripped - fan off- cause unknown.
TABLE 3: POST MITIGATION MEASUREMENT RESULTS
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VI. COST INFORMATION
The cost of the ventilation system restoration was $10,340. The work performed was
limited to the items listed in the initial investigation conclusions section. The cost per square foot
equates to $0.40.
VII. CONCLUSIONS
This case study illustrates the importance of performing diagnostics and understanding
the impact a building's ventilation system can have on radon concentrations. The restoration of
the ventilation system reduced radon concentration below 4 pCi/L and significantly increased the
outdoor air ventilation rates. The subslab supply air ductwork concerns appear to have been
justified based on the continuous radon measurement results. In many cases, subslab ductwork
can impact the successfulness of a ventilation strategy as well as an ASD strategy. Its impact
must be carefully evaluated.
With the ventilation fans operating continuously during occupied times, radon
concentrations are maintained below 4 pCi/L and the classrooms are being mechanically
ventilated with outdoor air rates that were recommended when the school was built (ASHRAE
standard 62 recommended 10 cfrn/person in 1968). However, the building occupants have
complained of temperature discomfort on cold days. This condition is due to the inherent
limitations of using residential equipment in a school building. Due to temperature discomfort,
the decision was made to change the ventilation fan's operation from continuous to cycling
during occupied hours. The selection of the ventilation restoration as a stand alone mitigation
strategy may prove to be unacceptable.
This case study reemphasizes the need to recognize the ventilation system as a radon
control system. The introduction of properly conditioned outdoor air to meet ventilation
standards is essential to the effectiveness of a ventilation based mitigation strategy. Without the
continuous introduction of outdoor air, radon levels are not consistently reduced to below 4
pCi/L. Therefore, the possibility of a combined strategy (ASD and proper ventilation), is now
being considered by EPA to ensure radon levels are consistently below 4 pCi/L when the
building is occupied.
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