United States
Environmental Protection
Agency
Office of
Research and Development
Washington, DC 20460
EPA/625/6-91/029
July 1991
xvEPA Handbook
Sub-Slab Depressurization
for Low-Permeability Fill
Material
Design & Installation of a
Home Radon Reduction
System
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EPA/625/6-91/029
July 1991
Handbook
Design and Installation of a Home Radon Reduction System-
Sub-Slab Depressurization Systems in Low-Permeability Soils
by
Charles S. Fowler
Ashley D. Williamson
Bobby E. Pyle
Frank E. Belzer
Ray N. Coker
SOUTHERN RESEARCH INSTITUTE
Birmingham, AL 35255-5305
(Under EPA Cooperative Agreement CR814621-01-0)
David C. Sanchez, Project Officer
AIR AND ENERGY ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NC 27711
Printed on Recycled Paper
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Notice
This document has been reviewed in accordance with the U.S. Environmental Protection Agency's peer and
administrative review policies and approved for publication. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
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Contents
Page
Notice »••••»• ii
Figures v
Tables ,.. v
Acknowledgments vi
Metric Conversion Factors vii
Section 1 About Radon 1
Section 2 About Sub-Slab Depressurization , 3
SectionB Gathering Information . . 5
House Summary Information , 5
House Differential Pressures ^ 5
Radon Entry Points —.5
Sub-Slab Pressure Field Extension Measurements 5
Sub-Slab Pressure-Flow Characteristics 9
Steps for Determining House Differential Pressures 9
Steps for Conducting a Radon Sniff Using Alpha Scintillation.; 9
Steps for Determining the Sub-Slab Pressure Field Extension 12
Steps for Making Sub-Slab Pressure-Flow Measurements 16
Section 4 Planning the System 19
Determining the Number of Suction Points 19
Determining Suction Hole Placement . 19
Closets 19
Room Corners 19
Stem Walls 19
Garages... 25
Determining the Size and Capacity of the Fan to Be Used .....25
Airflow 25
Durability 25
Purchase and Operating Costs 25
Noise ,; 25
Interior/Exterior Use 27
Sealing 27
Inlet/Outlet Size. : 27
Determining the Optimum Pipe Size(s) for the System , 27
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Contents (Cont.)
Section 5 Installing the System 31
Selecting the Specific Center for Drilling 31
Drilling the Slab Hole 31
Excavating the Suction Pits 31
= Finishing the Suction Hole , 31
Other Types of Installations .32
Garage Installation 32
Exterior Installation 32
Piping Layout and Fan Placement 32
Attic Piping . 32
Attic Fan Placement ; 38
Roof Penetrations 38
Exterior Piping 38
Section 6 System Indicators and Labeling , 41
Glossary 43
Abbreviations 45
References ;....; 47
Regional Training Centers ....« 49
iv
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Figures
Number
1 Floor plan for sample house ,..
2 Differential pressure measurement log sheet
3 Differential pressure measurement zones ,
4 Radon sniffs locations for sample house
5 Sniffer data sheet used to record measurements.
6 Pressure sample hole locations .' .
7 Approximate pressure contours from a suction hole in a representative
house plan
8 Flowchart for deciding the number of suction points to be planned
9 Minimum number of suction holes based on effective radius of extension,
r, and area of slab ...
10 Suction hole placement for sample house .
11 Likely suction hole placement for an L-shaped house
12 Example of "boxing in" construction technique
13 Graphs indicating fan curves and sub-slab flow curves
14 Decision process for fan/blower selection
15 Friction chart for average pipes
16 Typical interior suction point
17 Garage suction pipe installed horizontally under house slab
18 Garage suction pipe installed at 45-degree angle under house slab
19 Exterior suction hole installation
20 Attic piping layout for the sample house plan of Figure 1
21 Schematic of the fan placement and roof penetration of a typical installation.
Page
...8
.10
.11
.13
.14
.15
.17
,20
.21
.22
.23
.24
.26
.28
.30
.33
.34
.35
.36
.37
.39
Tables
1 Slab characteristics form
2 Heating/cooling systems, appliances, and bypasses
3 Approximate friction loss equivalencies for various pipe fittings.
...6
...7
.29
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Acknowledgments
The comments and input of the editorial review committee were invaluable: David E. Hintenlang of the
University of Florida; Marie S. Nowak of the National Association of Home Builders National Research Center;
William J. Angell of the Midwest University Radon Consortium and the University of Minnesota; Tonalee
Carlson Key of the State of New Jersey, Department of Environmental Protection; D. Bruce Henschel and James
B. White of the U.S. EPA, Air and Energy Engineering Research Laboratory (AEERL); and Dave Murane of the
U.S. EPA, Office of Radiation Programs.
The contributions of Randy McRae and the staff of the Center for Instructional Development and Services at
Florida State University have greatly enhanced the readability of this manual.
We would like to thank Terry Brennan and Wade Evans of Camroden Associates for their assistance in
developing and implementing the mitigation plans for some of the earliest houses for which the systems discussed
herein were designed. Thanks to Mike Gilley, formerly of the Polk County Health Department and currently with
the Florida Department of Health and Rehabilitative Services, and Wesley Nail, Tom McNally, and Lee Forgey,
all of the Polk County Health Department, for their invaluable contributions and cooperation throughout this
project Also, thanks to the EPA Project Officer, David C. Sanchez, and the entire Radon Mitigation Branch
(AEERL) for their capable and constructive assistance, support, and encouragement in this project.
Special thanks are in order for Ken Kirby of Southern Research Institute; Terry Brennan of Camroden
Associates; Arthur G. Scott of Arthur Scott and Associates; and D. Bruce Henschel and Merrill D. Jackson, both
of AEERL, for their review and valuable comments on earlier versions of this manuscript. Many of the
illustrations were drawn by Thomas J. McGuire of Southern Research Institute.
Finally, our deepest gratitude goes to the homeowners who opened their houses for diagnostics, installations,
and monitoring of systems. Their patience, hospitality, and endurance were most appreciated.
VI
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Readers more familiar with the metric system may use the following factors to convert'to that system.
Metric Conversion Factors
Nonmetric
Multiplied by
Yields Metric
°F
-I
ft^
ft-Vmin (cfm)
gal.
in.
in. WC
in.2
mil
pCi/L
5/9 (°F-32)
0.305
0.093
0.028
0.00047
3.785
2.54
0.249
6.452cm2
25.4
37.0
nrVsec
L
cm
kPa
Bq/nr
VII
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Section 1
About Radon
Radon is a radioactive gas which comes from the
natural decay of uranium. It moves to the earth's surface
through tiny openings and cracks in soil and rocks. High
concentrations of radon can be found in soils derived from
uranium-bearing rocks, such as pitchblende and some phos-
phates, granites, shales, and limestones. It may also be
found in soils contaminated with certain types of industrial
wastes, such as the by-products of uranium or phosphate
mining, or from industries using uranium or radium.
In outdoor air, radon is diluted to such low concentra-
tions that it is usually nothing to worry about. However,
radon can accumulate inside an enclosed space, such as a
home, posing a threat to people.
The only known health effect associated with exposure
to elevated levels of radon is an increased risk of developing
lung cancer. Scientists estimate that about 20,000 lung
cancer deaths a year in the United States may be attributed to
radon. In general, the risk of developing lung cancer in-
creases as the level of radon and the length of exposure
increase.
Radon can seep into the home in numerous ways: through
dirt floors, cracks in concrete floors and walls, floor drains,
sumps, joints, and tiny cracks or pores in some hollow-block
walls. This seepage of gases into the house most often
occurs when air pressure inside the house is lower than air
pressure outside, or underneath,, the house. In this case,
cracks or other openings in the house allow radon-laden gas
to be pulled inside.
Since radon is a colorless, odorless, and tasteless gas,
the only way to detect its presence is to sample and analyze
an area's air using a conventional radon measurement test. If
the test reveals elevated radon levels, the homeowner will
have to decide what steps to take to reduce the levels. The
higher the level of radon present in a home, the more likely
an active radon reduction system (such as sub-slab depres-
surization) may be required. Lower radon levels may require
only a passive reduction system, such as simple sealing.
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Section 2
About Sub-Slab Depressurization
While several methods exist for reducing radon concen-
trations in the home, sub-slab depressurization (SSD) is gen-
erally the most common and most effective radon reduction
strategy in basement and slab-on-grade houses. Sub-slab
depressurization reduces the pressure in the sub-slab envi-
ronment by exhausting sub-slab gases before they can move
through floor cracks or openings into the house.
An SSD system consists of one or more pipes attached
to a fan or blower which creates a suction. The pipes usually
originate in a pit dug into the fill material underneath the
concrete slab flooring of a house. The pipe is typically
concealed in a closet corner or an unfinished area. Where
possible the piping is routed upward to the attic and vented
through the roof.
Installation of an SSD system can typically reduce in-
door radon levels by 80 to 99+%. The higher reductions are
usually achieved when the fill material directly under the
slab has a high permeability. The highest permeabilities
result when the sub-slab fill material is imported crushed
rock or gravel. If the permeability is low, more suction pipes
may be needed, and positioning of the pipes becomes more
important
NOTE: In this manual the term "permeability"
is used in the generic sense to mean a measure
of the ease with which a fluid (liquid or gas)
can flow through a porous medium. Sub-slab
permeability generally refers to the ease with
which soil gas can flow underneath a concrete
slab.
Although gravel is more permeable, its scarcity in
some areas makes soil the primary fill material under the
concrete slab flooring. Most soils, however, especially those
with any degree of compaction, have low permeability. Moist
soil is also less permeable than dry soil.
Since much of the existing literature about SSD systems
addresses slabs poured over gravel or other more permeable
materials, this booklet addresses designing and installing
SSD systems to work in less permeable fill material.
NOTE: Homeowners imay not have all the
tools and equipment necessary to design and
install an optimal SSD system for their houses.
SSD mitigation systems are best designed and
installed by trained mitigation contractors,
knowledgeable in house construction and the
principles of radon entry. In cases of low
indoor radon concentrations, homeowners may
successfully use less expensive methods them-
selves. Two sources of information on other
radon reduction techniques include Radon Re-
djiction Techniques for Detached Houses, avail-
able from the U.S. EPA, and Practical Radon
Control for Homes, by Terry Brennan and Su-
san Galbraith, published by Cutter Information
Corporation. Other souirces for additional in-
formation appear in the References section at
the end of this publication.
In addition to installing ian SSD system, or with any
other method of mitigation, sealing obvious radon entry
points, such as slab cracks, bath openings, and toilet open-
ings, is a useful, if not essential, component for successful
mitigation. Uremane caulk is generally preferred because it
commonly bonds better to concrete.
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Section 3
Gathering Information
Once it is established that a radon problem exists, cer-
tain basic house information needs to be obtained, and addi-
tional diagnostic tests should be run. The data gathered from
these sources will be used to design the sub-slab depressur-
ization system for that particular house. The types of addi-
tional data include:
House summary information
House differential pressures
Radon entry points
Sub-slab pressure field extension measurements
Sub-slab pressure-flow characteristics
If the mitigator is working with other crew mem-
bers, the steps for gathering this data may overlap. However,
if the mitigator is working alone to gather this information,
the suggested order for completing these steps is:
1. Gather the house summary information.
2. Determine the house differential pressures.
3. Drill and seal the pressure field extension
measurement suction and test holes.
4. Conduct the radon "sniff."
5. Measure the sub-slab pressure field extension.
6. Measure the sub-slab pressure-flow
characteristics.
House Summary Information
The house summary provides a functional diagram of
the house and serves as a valuable reference when planning a
sub-slab depressurization system.
Information for the summary can be gathered from the
homeowner's existing knowledge or from plans, documents,
or pictures taken during construction or renovations. Other
information may be visually noted or measured during a visit
to the house. The sample forms of Tables 1 and 2 on pages 6
and 7 are abstracted from EPA's recommended house sum-
mary information forms. They illustrate some of the house
information you may wish to compile. Much of the informa-
tion on these forms will help the mitigator design an SSD
system for a particular house. The rest of this information
may help the mitigator recall specific house features.
Figure 1 on page 8 represents the floor plan of a house
which measures approximately 2,300 square feet of living
space. (This house will be used as the example throughout
the booklet) When compiling a house summary, a diagram
such as this, along with other information gathered, will help
shape future decisions about the SSD system. Examples of
important features to note include a sunken living room
(approximately 4 in. below the remaining house slab), ce-
ramic tile flooring in bathrooms, and vinyl tile in the kitchen
and in the breakfast and family rooms.
House Differential Pressures
Soil gases are typically pulled into almost every house
as a result of a lower air pressure inside the house than
outside. When gathering data it is helpful to know the extent
of these differences, which serve as "driving forces" to pull
radon-laden soil gas into the house.
These driving forces are usually caused by environmen-
tal factors (wind or temperature), household appliances (heat-
ing/cooling system air handler or exhaust fans), and occupant
effects (closing certain interior doors).
The differential pressure mezisurement is a test that EPA
recommends as a core measurement. An effective SSD
system will have to overcome the typical magnitude of the
house depressurization measured, by this procedure. Steps
for determining the differential pressure measurement appear
on page 9.
Radon Entry Points
A visual inspection of the house provides an excellent
opportunity to check for potential! radon entry points into the
building shell. The cracks and utility penetrations noted in
the house summary are likely candidates, and there may be
other potential radon entry points.
One current technique for detecting radon entry points
almost instantly is called the radon sniff. There are several
devices for conducting a radon sniff; however, one of the
most common methods involves clrawing sampled air through
a filter into a scintillation cell, which is used to measure the
radon concentration. The radon sniff is strictly a diagnostic
tool and has no formal EPA protocol; however, a standard
procedure for conducting the test appears on page 9.
Sub-Slab Pressure Field Extension Measurements
All of the information gathered before this point is
useful regardless of the mitigation plan to be used. However,
when planning an SSD system, the most useful information
comes from the sub-slab pressure field extension measure-
ments and the sub-slab pressure-flow characteristics. The
sub-slab pressure field extension measurement is the most
useful diagnostic for determining the location and number of
suction holes. From this measurement, the effective pressure
field radius of extension, r, can be determined for each slab,
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Table 1. Slab Characteristic* Form.
House Identification:
Depth of floor below grade (ft): Front:
Right:
Back:
Left:
Average depth of total slab below grade (ft):
Area (ft2):
Slab:
A - floating
B - on stem wall
C - monolithic
D - unknown
If slab is on stem wall,
slab location relative to
foundation wall:
A-top
B - in L-block
C- unknown
Interior sub-slab
footings:
A-yes
B-no
C - unknown
Sub-slab media/aggregate:
A - grave! B - soil C - mixed D - unknown
Floor cover
none
dirt
carpet
tile/linoleum
wood
terrazzo
other
Wall cover
paint
sheet rock
plaster
wood paneling
other
none
Relative %
Exterior wall construction:
A - poured concrete
B - cinder block
C - concrete block
D - stone
0 - brick
F - wood
G - other
Potential radon entry routes through slab
Floor/wall joint: (yes, no, unknown) Width (in.): Total length (ft):
Total length of all other cracks (ft): < 1/16 in. width:
Utility penetrations: • (number sealed)
> 1/16 in. width:
(number unsealed)
Sump: (yes.no) Number of floor drains:
Empty to:
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Table 2. Heating/Cooling Systems, Appliances, and Bypasses.
Primary system:
A - forced air A - g
B - hot water B - o
C - radiant C - c
D - stove/fireplace D - v\
E - other
Primary location of ducts
supply: return: _
A - basement C - living area E
B - sub-slab D - attic
Central AC (yes, no):
Window AC units (#): .
Fuel:
as E - electric
il F - solar
oal G - kerosene
rood H - other
Furnace location:
A - basement
B - first floor
C - garage
Are ducts insulated:
~ A - yes C - part
- other B - no D - unknown
D - duct strips
E- attic
F - other
Size of air
handler (cfm):
Heat recovery ventilator rated HRV
(HRV): capacity operation
A - wall C - none
B - ducted D - unkr
(cfm):
)
lown
Supplementary heat Location Use % Fresh air Locations
fireplaces FP1
(#v FP2
FP3
wood/coal WS1
stoves (#): WS2
kerosene heaters KH1
(#): KH2
Appliances Location
range/oven
water heater
clothes dryer
Fuel % Fresh air
A - basement
B - 1 st floor
C - 2nd floor
D - other
(hrs/day):
Use (days/year)
A - none
B - 1 to 20
C- 21 to 50
D - over 50
E - unknown
Locations Fuels
A - basement A - gas
B - 1st floor B- electric
C - garage C - propane
D - other D - other
Fans
whole house
attic exhaust
range hood exhaust
window (exhaust)
window (supply)
bathroom exhaust
Yes/No
Number
Type air cleaning system:
A - simple filter
B - electrostatic
C - membrane filter
D- none
Jhimney (ft*):
JBalloon wall framing (y/n):
)pen stair ways (#);
.aundrv chutes (#):
Plumbing chases (ft2):
Attic access doors (y/n): _
Recessed ceiling lights (#):
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Utility
Porch
Breakfast
Room
Garage
Kitchen
Family
Room
Dining
Room
Porch
0>
V)
.o
f •)
Foyer
Q. .
9 I
Bedroom
o>
V)
.o
o
Jloset
Bath
Lin
Living
Room
0)
Bedroom
Bedroom
V)
JD
o
Bedroom
Closet
Bath
10ft
Flfluro 1. Floor plan for sample house.
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indicating the likely coverage area from a particular suction
point. Steps for determining the sub-slab pressure field
extension appear on page 12.
NOTE: Sub-slab pressure field extension may
be limited in at least two ways.
(1) The pressure field cannot extend past the point
where there is a footing or other obstruction
through which the air cannot flow; therefore, it
is important to treat each slab separately. (2)
The pressure field cannot extend past the point
where there is a crack or other high-permeabil-
ity access to indoor or outdoor air. At both of
these points, the pressure field is effectively
"lost."
Sub-Slab Pressure-Flow Characteristics
The pressure-flow characteristics will be used to deter-
mine the nature of the sub-slab environment, to estimate the
optimum pipe size, and to select the proper fan or blower,
Steps for determining the sub-slab pressure-flow characteris-
tics appear on page 25.
Steps for Determining House Differential
Pressures
Materials:
• Manometer, 0-0.024 ± 0.002 in. WC (0-6 ± 0.6
Pa)
• Two lengths of flexible (but not collapsible)
tubing of a diameter to fit snugly on the
manometer ports, long enough to reach from
anywhere in the house to an outside door
• Some type of wind diffuser (fritted glass, cotton
wick, etc.) to go in one end of tubing
House floor plan
Procedure:
1. Visually inspect the house to identify zones that
may be separated from one another by closed
doors. Designate them on the floor plan.
Likewise identify locations of air returns and
supplies, and appliances which may potentially
depressurize the house (driers, vent fans,
combustion appliances, etc.). Mark them on
the floor plan.
2. From a convenient location, run one length of
the tubing from the REFERENCE port of the
manometer to the outside of the house through
a door that will close over the tube without
pinching or severing it. If there is any
appreciable wind, protect the exposed end of
the tubing with some type of diffuser. Run the
other length of the tubing from the SIGNAL
port of the manometer to the space to be tested.
3. Close all exterior doors, windows, and other
openings.
4. With all interior doors open, and the air handler
and all potentially depressurizing appliances off,
measure and record the house differential
pressure.
5. With all other conditions the same, turn on the
air handler and measure; and record the house
differential pressure. Do the same with as many
of the depressurizing appliances as desired, and
possibly with as many as required, to give a
"worst case" scenario. Record all measurements
on the Differential Pressure Measurement Log
(Figure 2, page 10).
6. Repeat step 5 either with all or with selected
interior doors closed. Sample with the SIGNAL
tube in the same space as the air return, and
with it in a space (or zone) without an air
return. Record all measurements.
EXAMPLE: Figure 3 on page 11 illustrates the zones
tested in the sample house. In this house, the kitchen/
breakfast room area, the family room, the hallways, the
foyer, and the living room will be somewhat depressurized
(indicated D) any time the air handler is on. There are no
barriers (doors or walls) that prevent free air movement from
these spaces to the central air return. Therefore, these rooms
together make one zone.
When the interior doors are closed, the dining room and
each bedroom and bath are isolated from the central return,
but they all have supply registers; so these spaces are slightly
pressurized (indicated P).
The utility room has a supply register, and the door is
normally closed; but if the dryer is operating, the space may
be depressurized. If the dryer iis not operating but the air
handler is, the space is probably slightly pressurized. There-
fore, the room is labeled M for mixed.
The garage has no supply register, nor is it normally in
communication with the return. The front porch and stoop
are open, and the back porch is a screened porch, so they are
treated as outside the building shell. ,
Steps for Conducting a Radon Sniff Using Alpha
Scintillation
Materials:
Alpha scintillation (flow-through) cells,
approximately 200 ml
Portable photomultiplier tube scintillation
counter
• Small diameter flexible tubing
• 0.8 nm filter assembly
Small hand or battery pump (capable of pulling
about 1 L/min)
• Rope caulking
• House floor plan (optional)
Procedure:
1. Prior to the house visit, purge all scintillation
cells with aged compressed gas (air or nitrogen)
and perform a 2- to 10-raiinute background count.
Affix the dated background count to each cell.
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Differentia! Pressure Measurement Log
Occupant Name:
Technician:
Instrument:
House ID:
Date:
Differential Pressure Measurements
Measurement Number
Type of Measurement
Location
Measurement Condition
Date/Time
Measurements
Measurement Number
Type of Measurement
Location
Measurement Condition
Date/Time
Measurements
Measurement Number
Type of Measurement
Location
Measurement Condition
Date/Time
Measurements
8
Figure 2. Differential pre*ture measurement log sheet.
10
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M
D
Air Return
-t
D
r-
D
Figure 3. Differential pressure measurement zones. Inside bold line is a single zone because It cannot be subdivided by a door.
11
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Only cells with less than 5 cpm should be used
for most in-house sniffs. Cells with larger
background counts should be used for sub-slab
sniffs only.
2. Visually inspect the house to identify and tag
locations for obtaining radon sniffs. Sample
points should include at least one penetration
(point of entry) for each of the four perimeter
walls; plumbing penetrations in the floor and/or
walls; any expansion joints, slab interfaces, or
other detectable cracks in the slab; and holes
drilled for the sub-slab communication test.
Locate any other slab penetrations, and mark
all locations on the floor plan.
Figure 4 on page 13 illustrates locations for radon sniffs
in the sample house.
3. Take sniffs from sample points with a sample
train connected in the following manner. Attach
1 ft of tubing to the filter assembly. Use 1 ft
more of tubing to attach the filter assembly to
one pole of the scintillation cell. Use 1 ft or
more of tubing to attach the second pole of the
cell to the intake of the air pump.
Place the cell in the scintillation counter so it
can be counting before, during, and after pulling
sampled ah* through the apparatus. Allow at
least a 1-min delay after the cell is placed in the
counter before starting. (This minimizes
spurious scintillations produced by ambient
light) The counter should be set on about-1-
min intervals for sampling and counting.
4. Take sniffs from each identified location by
placing several inches of the sampling tube into
the opening being sampled. If the crack or
opening is too small for the tube to be inserted,
caulk the tube to the opening in such a way as
to minimize the amount of room air being drawn
by the sampler. Sample for several minutes at
each location. Identify the sample with its
location (use house plan if available), and record
the data on the Sniffer Data Sheet (Figure 5,
page 14).
Communication test holes that are used as
sample points for the radon sniff should be
closed off to prevent infiltration of ambient air
into the space being sampled. Use rope caulk
to plug gaps around sampling lines, or a plastic
sheet and tape on flat surfaces.
5. After sampling, purge the cell with aged ah- or
outside air. (Inside air will work if indoor
concentrations are less than 5 pCi/L.)
6. If a high source of radon is detected, purge the
cell immediately. If counts do not reduce
sufficiently, change to a fresh cell. Sample
sub-slab test holes last, because they are
expected to have higher radon concentrations.
EXAMPLE: Figure 4 plots potential radon sniff loca-
tions for the sample house. The locations labeled "WO"
represent wall outlets. Notice there is at least one on each
perimeter wall. An inset wall outlet may be the closest the
mitigator can come to finding a possible floor/wall crack or
seam, or to finding potentially unsealed or poorly closed
concrete block holes in direct communication with the below
grade stem wall and footing.
The 'TP" represents plumbing penetrations (sewer pipes
and hot or cold water pipes). The pipe penetrations in the
utility room are for the washer; the ones in the kitchen are
under the sink; and the ones in the bathrooms are under the
lavatories. Other penetrations that should be checked are the
toilet bases (TB) in each bathroom, and the bath tub trap
(TT), if it is accessible.
The final location labeled is the slab seam (SS) in the
corner of the living room. It is formed where the sunken
living room slab interfaces with the house slab. If any slab
cracks are detected while drilling test holes or performing
other investigations where the slab is exposed, those cracks
may also be sniffed.
Steps for Determining the Sub-Slab Pressure Field
Extension
Materials:
• Industrial vacuum cleaner, 100 cfm @ 80 in.
WC
• Micromanometer, 0-20 in. WC + 1% @ 0.004
in. WC (0-5000 Pa, ± 1% @ 1 Pa)
• Speed control for vacuum cleaner
• 3/8" or 1/2" hammer drill, masonry and impact
drill bits
• Rope caulking
• House floor plan
Procedure:
1. Visually inspect the house substructure to
identify the area of below-grade and on-grade
floor slabs and walls and their distribution in
the house layout. Determine, if possible, the
most likely sub-slab routes of freshwater lines,
sewage lines, gas lines, and any other utilities
that may affect the choice of drilling sites.
2. From the above information, determine the
location for (a) suction test hole(s), and (b)
pressure sample holes.
a. Suction test hole(s) should be located anywhere
between 6 ft and 15 ft from the nearest exterior
wall, and no closer than 30 ft from one another.
They should also be located so as to maximize
area and floor/wall joint coverage within a 15-ft
radius of the suction hole.
b. Pressure sample holes should be located, as
available, at radial distances of 3 ft, 9 ft, and 15
ft from the nearest suction test hole. Sample
holes should be located in two or three direc-
tions from each suction test hole. Locate at
least one pressure sample hole (scaling baseline
hole) about 1 ft from each suction hole. Record
the location of all holes on the house floor plan.
(See Figure 6, page 15.)
12
-------
wo
WO PP
pp
PP
TB
TT
WO
SS
WO
PP
TB
Figure 4. Radon sniffs locations for sample house.
13
-------
Sniffer Data Sheet
House ID:
Date/Time:
Technician:
Sample Number
(Mark on Floor
Plan and Tape)
Scintillation Sample Length
Cell Location of
Number Interval
Counting Comments
Instrument
Figure 5. Sniffer data sheet used to record measurements.
14
-------
(scaling i
baseline) >
(suction
hole)
ID
A
\!
\
Figure 6. Pressure sample hole locations.
15
-------
3. Drill one suction test hole (sized to match the
vacuum cleaner nozzle) through the slab at the
designated location(s) and temporarily seal the
hple(s) with rope caulk. Make certain the drill
bit penetrates through the slab, through the vapor
barrier, and well into the fill material. Be
careful to feel for any sub-slab obstruction.
4. Drill the 3/8 in. or 1/2 in. pressure sample holes
and seal as above.
5. Wait 15-30 minutes after the sample holes have
been sealed, then take the sub-slab gas samples
as described in the radon sniff test.
6. With the suction hole(s) and pressure sample
holes drilled as directed, measure the pressures
at each of the pressure sample holes before
operating the vacuum cleaner.
These measurements will indicate the natural
deprcssurization caused by the environment and
the normal depressurization caused by
appliances.
NOTE: Pressures at the sample holes are
measured by placing the end of the sampling
tube into the test holes. Some means of
providing an airtight seal between the tube and
the drilled hole are necessary. Rope caulking is
the recommended material for creating this seal.
7. Place the micromanometer to measure the
suction induced at the scaling baseline hole of
the suction hole being tested. (The scaling
baseline hole is the pressure sample hole located
1 ft from the suction hole.)
8. With the vacuum cleaner set to produce about a
1.5-2 in. WC (375-500 Pa) pressure differential
at that baseline hole, make pressure field
measurements at the pressure sample holes,
starting with the ones closest to the suction hole
and moving out
NOTE: At most of the close pressure sample
holes, some differential pressure may be
measured; but at some of the more distant
sample holes, more than likely no consistent
reading will be possible.
9. Record the pressures measured at each sample
hole and compare them with the pressures
measured before the vacuum cleaner was run.
The pressure induced by the vacuum cleaner
should decrease as you move farther from the
suction hole. The greatest distance from the
suction hole at which a pressure greater than or
equal to the greatest house differential
measurement was recorded should be taken as
the effective radius of extension, r, for that
pressure field. However, the effective radius of
extension should not be greater than the
minimum distance from the suction hole where
no vacuum-induced pressure could be detected.
It is important to remember that, in low-permeability
soils, sufficient time must be allowed for the pressure field to
be established (3-5 minutes for close test holes and succes-
sively longer times for the more distant ones).
In the sample house represented in Figure 7 on page 17,
the effective radius of extension, r, is about 18 ft.
Steps for Making Sub-Slab Pressure-Flow
Measurements
Materials:
• Industrial vacuum cleaner, 100 cfm @ 80 in.
WC
• Micromanometer, 0-20 in. WC ±1% @ 0.004
in. WC (0-5000 Pa, ± 1% @ 1 Pa)
• Device to measure flow at vacuum cleaner inlet
(hot wire anemometer, calibrated orifice, vane
anemometer, rotameter, Pitot tube, or electronic
anemometer)
• Speed control for vacuum cleaner
3/8" or 1/2" hammer drill, masonry and impact
drill bits
• Rope caulking
Procedure:
1. Connect the industrial variable speed vacuum
cleaner, with an airtight seal, to the suction test
hole. Have on-line and ready the devices to
measure the flow into the vacuum cleaner and
the suction at the scaling baseline hole (about 1
ft from the suction hole).
2. Operate the vacuum cleaner at a speed so as to
produce 0.8 in. WC (200 Pa) of suction at the
scaling baseline hole. Record the suction and
flow at that setting.
3. Increase the vacuum cleaner speed so as to
produce 2 in. WC (500 Pa) and 5 in. WC (1250
Pa) suctions at the scaling baseline hole while
measuring and recording these suctions and the
flows into the vacuum cleaner.
NOTE: The pressure at the scaling baseline
hole and the flow measurements from the suction
test hole are the values that will be used to plot
the sub-slab flow curve for the house and soil
beneath it
16
-------
Figure 7. Approximate pressure contours from a suction hole in a representative house plan.
17
-------
-------
Section 4
Planning the System
Determining the Number of Suction Points
With the data gathered from the pressure field extension
measurement, you can now determine the minimum number
of suction holes needed to effectively reduce indoor radon
concentrations. Other information used to make this deci-
sion includes the number of slabs in the house, the size of
each slab, and the existence, location, and influence of any
interior footings, sunken or elevated slab areas, expansion
joints, sub-slab obstructions, or geometry features that may
limit sub-slab communications. Figure 8 on page 20 illus-
trates some of the ways decisions may be made taking these
factors into account.
Once the effective radius of extension from the suction
hole is determined, the next input required is the approxi-
mate area (in square feet, ft2) of the slab being considered.
(The sample house measures approximately 2,300 ft2.)
Figure 9 on page 21 is a graph used to determine the
number of suction holes required for a given slab. (This
graph was developed on basic geometric relationships be-
tween an area and a radius.) The effective radius of exten-
sion is plotted on the x-axis (from right to left), and the area
of the slab is plotted on the y-axis. The diagonal lines divide
the regions of the effective coverage area of the indicated
number of suction holes.
Find the effective radius of extension, r, that was deter-
mined and go straight up parallel with the y-axis until you
find the area of the slab. The region between the diagonals
where the radius and area intersect indicates the approximate
minimum number of suction holes required by that slab. For
the sample house, the minimum number of suction holes
would be three.
This number may need to be increased if features such
as those described above seem to limit communications.
Erratic results of the communication test indicate the possi-
bility of such a condition.
One other factor to consider before deciding how many
suction holes to install is whether the soil moisture may vary
much beneath die slab because of rainfall or water table
movement. Soil permeability varies with soil moisture. If
the diagnostic test is made when the sub-slab soil is unusu-
ally dry, the soil permeability and the pressure field exten-
sion will probably be greater than it would be if measured
during a wetter season. In this case, you may want to
increase the number of suction holes per given slab area.
Determining Suction Hole Placement
It is easier to plan SSD systems to be installed in unfin-
ished basements where there are few restrictions on suction
hole placement SSD systems for finished basements and
other finished spaces, particularly slab-on-grade houses, are
more difficult to plan.
A floor plan drawn to scale, perhaps one on which the
sub-slab communication is plotted, is a helpful tool at this
point. Sketching in the effective areas of pressure field
extension from various suction hole placements will give an
idea of the configuration that will ensure the best suction
coverage of the slab. Figure 10 on page 22 illustrates the
suction hole placement for the sample house. Figure 11 on
page 23 illustrates the likely sucition hole placement for an L-
shaped house. Following are some possible locations for
suction hole placement. Installation techniques for these
methods are detailed in Section 5.
NOTE: Geometry suggests that holes located
about one effective radius of pressure extension,
r, away from the closest exterior wall(s) will
give the widest coverage. However, soil near
the edge of a slab often has not been compacted
as well as that near the center of the slab,
producing a settling space between the top of
the soil and the bottom of the slab, or just a
more permeable trench near the perimeter of
the slab.
In this case, if the diagnostic communication
test indicates a greater pressure field extension
from a perimeter suction hole, then the suction
holes should be placed! near the perimeter. If
the communication test shows much greater
flows from perimeter holes without much greater
pressure field extension, then slab cracks or
other leakage is probably limiting the pressure
field extension, and perimeter suction holes
should not be used.
Closets. Often the best location for suction hole place-
ment is in the corner of a closet. Installations there arc less
noticeable and less obtrusive.
Room Corners. If closets are not spaced to give full or
adequate pressure field coverage, you may be able to place a
suction hole in the corner of a room and conceal the pipe by
boxing it off. Figure 12 on page 24 illustrates this procedure.
Stem Walls. In some cases it is possible to use an
exterior suction hole penetrating horizontally through a stem
wall beneath the slab, rather thzin vertically through the slab
in an interior space. In this case, the stem wall must be
accessible from outside the house, and there must be mini-
19
-------
With any mitigation system, major
openings and cracks in the slab
should be closed.
Determine the number of separate
slabs In living space.
For each slab, determine If there are
any interior footings, sunken slab
areas, obstructions, or corners that
may hamper or prevent
communication to any other part of
the slab.
Determine if pressure field extension
measurements indicate unreached
areas of any slab.
Decision Criteria
At least one suction point for each
major slab.
If holes can be placed so as to
bridge the discontinuity under a
slab or between slabs, do so;
otherwise plan at least one suction
point for each isolated area.
Determine minimum number of
suction holes per slab area using
Figure 9.
Figure 8. Flowchart for deciding the number of suction points to be planned.
20
-------
4000
1000
CM
.SS
C/D
100
15 12.5 11 10
Effective Pressure Field Radius of Extension, r (ft)
Figure 9. Minimum number of suction holes based on effective radius of extension, r, and area of slab.
21
-------
TO"
Flgura 10. Suction hole placement for sample house.
22
-------
Bedroom
o>
V)
o
a
Bath
Bedroom
Closet
Utility Room
Garage
Bedroom
0 Closet
Bath
Family
Room
Kitchen
Foyer
Dining
Room
step down
Living
Room
Bedroom
o
Closet
Bath
10ft
Figure 11. Likely suction hole placement for an L-shaped house.
23
-------
Trim and paint to match
existing wall finish
1.5- to 4-ln. PVC pipe to the attic
fan
Furring strips
Figure 12. Example of "boxing In" the suction pipe In a corner of a room where no closet corners are close enough to extend the
pressure field.
24
-------
mal loss of pressure field extension from slab cracks or other
stem wall leakage.
NOTE: In slab-on-grade houses, avoid stem
wall placement and perimeter wall placement if
the footing is on expansive soils, or if there
seems to be foundation or structural weakness
near the stem wall in question.
Garages. Some garages actually have a portion of the
house slab exposed at one end. Even if not, other garages are
a few steps down from the house floor level. In such
instances, the house stem wall may form the lower course or
two of the interior walls of the garage. Often this is a good
location for a horizontal penetration through the stem wall
beneath the slab if that portion of the slab cannot be treated
another way.
Determining the Size andCapacity of the Fan to Be
Used
Because the field mitigation experience in low-perme-
ability soils is still in an early phase, information about fans
and blowers is still being learned. A few fans, such as the in-
line centrifugal fan, have been designed for radon mitigation
situations. These usually are best for systems installed in
high-permeability fill material. Other fans will certainly be
developed as more data about fan use are gathered, espe-
cially in low-permeability fills. Generally, if less than 5-7
cfm of flow can be produced by the vacuum cleaner test,
then one of the high-suction, low-flow fans may be needed.
Several factors go into selecting the proper fan or blower
for an SSD system. Considerations include:
Airflow/suction capabilities
Durability
Purchase and operating costs
Noise
Suitability for interior or exterior use
Sealing requirements
Inlel/outlet size of the fan
Airflow. While the pressure field extension measure-
ments give a good approximation of an effective depressur-
ization radius, the pressure and flow measurements are indi-
cators of sub-slab permeability. Using the data gathered
from the pressure and flow measurements you can plot the
flow curve (airflow) for the sub-slab fill material.
The lower plot of Figure 13 on page 26 illustrates the
sub-slab flow curves for two houses built on soils with
different permeabilities. (Because both of these are soils,
these flows are not as great as would be measured in coarse
aggregate. Therefore, even the high-permeability soil is a
low-permeability fill material when compared to most gravel.)
The sample house falls between the two, closer to the higher
permeability. Also plotted in the upper and lower parts of
Figure 13 are fan performance curves taken from Reducing
Radon in Structures, the manual the EPA developed for its
radon mitigation training program, and from other published
fan company figures. (Fans generally operate more effi-
ciently in the middle range of their performance curves.) On
such a simultaneous plotting, the intersections of the soil
curves with the fan curves indicate about where the system
will operate. Generally, the fao or blower that intersects the
soil curve at a higher suction and higher flow will be more
effective in that soil.
Figure 13 suggests that for both soils, especially the one
with low permeability, the system will tend to operate near
the high-suction, low-flow end of the fan curves for the RDS,
R-150/K6, or radial blower. The fan curve data for the
vortex blower did not extend farther than the 6 in. WC
suction in the plot, but it obviously intersects both soil curves
at higher suctions and higher flows.
Durability. As suggested earlier, a lack of enough
information makes it unclear what the durability of a fan will
be when operated at low flows and relatively high suctions.
Some indications suggest fan failure may occur sooner when
operated in such environments. Also, because many fans are
placed in attics, high heat may further contribute to early
failure.
Purchase and Operating Costs. Again, the in-line
centrifugal fan has been developed for "use in mitigation
systems. Most of the higher suction fans available now are
built for other industrial applications. However, a few de-
signed for radon mitigation are beginning to be available on
the market Since research data have not been collected for a
long enough time in this area, it is not clear how to predict
the long-term costs of these various systems.
Currently, in-line fans have been kept fairly lightweight
and affordable. The blowers that produce higher suctions are
somewhat heavier and more costly to purchase. In addition
to purchase costs, the power requirements to operate these
various fans also differ. The lighter weight in-line fans
usually require less power than the higher suction blowers.
Another factor to consider is installation cost, and re-installa-
tion cost if the fan should have to be replaced at some point.
Included in the installation cost should be the wiring permit,
if required by local codes, but that should not differ between
fans.
Remember, though, there iis insufficient data to accu-
rately predict whether the smaller in-line fans have an overall
cost advantage over the larger, more powerful blowers.
Noise. In-line centrifugal fans are designed to run qui-
etly and have received little criticism from homeowners in
this regard. However, the larger, more powerful blowers,
especially those designed for industrial applications, produce
quite a bit more noise.
The noise factor can be dealt with by installing the fan
as far as possible from the living space, and by including
varying degrees of soundproofing material when the system
is first installed. Of course, this adds to the initial installa-
tion cost, and an extremely remote fan placement will require
longer piping runs, which may nxluce the system's effective-
ness. The newer high-suction fans often come with im-
proved soundproofing. The relative quality of what is avail-
able in local markets must be determined by the mitigator
and homeowner.
25
-------
c
o
O
c
o
0
Airflow (cfm)
Flfluro 13. Fan curve* for four different kinds of fans/blowers (top) with sub-slab flow curves for soils with two different
permeabilities plotted on an expanded air- flow scale (bottom). (Portions of these graphs were taken from Reducing
Radon In Structures.)
26
-------
Interior/Exterior Use. If the exhaust pipe from suction
holes in a basement is routed through a rim joist to the
outside, or if a suction hole in a slab-on-grade house is
through an exterior stem wall, the fan should be placed
somewhere outside the house. In that case, the fan and
wiring will need to be rated for exterior applications. In
some model lines these fans are more expensive, and gener-
ally the wiring for these fans will also be more expensive.
Sealing. Most fans, even some designed for mitigation,
may have to be partially disassembled to have potential
leakage areas sealed prior to installation. This is especially
true of industrial blowers designed to move large quantities
of uncontaminated air. Even though some fans may be
placed outside the living shell, opportunities exist for soil gas
with high concentrations of radon to reenter the living space
through attics, unfinished basements, garages, or windows.
The likelihood and projected cost of sealing should be con-
sidered when selecting the fan/blower for the job.
Inlet/Outlet Size. Generally, in-line centrifugal fans
have 4-in., 5-in., 6-in., or larger openings, whereas other
blowers may be quite a bit smaller or irregular in size. Also,
as the name suggests, in-line fans have their intakes and
exhausts along the fan axis. In most radial or vortex blow-
ers, the exhaust flow is perpendicular to the intake, thus
requiring a different design of the piping system and exhaust.
Figure 14 on page 28 represents the decision process for
fan/blower selection.
EeterminingtheOptimumPipeSize(s)fortheSystem
Airflow is the primary consideration in choosing opti-
mum pipe size. The same plots used in the decision-making
process for fan selection also aid the proper selection of pipe
sizing once the fan is chosen.
If the fan has been selected, then the point of intersec-
tion of the fan curve with the sub-slab flow curve will give a
good approximation of the airflow that can be expected in
the system. From the airflow estimate, use the chart in
Figure 15 on page 30 to estimate the friction loss in various
sizes of pipe.
NOTE: This chart is calculated for "average"
pipe, which is usually some type of iron pipe
with a given smoothness and having joints
estimated to be present at some regular
frequency. PVC pipe is less resistive to air
movement because of its greater smoothness.
Therefore, these approximations usually
overestimate the friction loss that would actually
be found in PVC pipe.
If the fan selected is one in which the sub-slab flow
curve intersection with the fan selected is in the 1.5-2 in. WC
range, you will probably want to keep the friction loss to 0.2-
0.4 in. WC per 100 ft of pipe. If the fan curve intersects the
sub-slab curve at something greater than 4 in; WC, then a
friction loss of 0.8-1.2 in. WC per 100 ft of pipe can be
tolerated.
To use the chart in Figure 15, find on the x (horizontal)
axis the airflow determined from the sub-slab fan curve
intersection. Go up until you are in the friction loss range (y-
axis) you determined as above. The closest pipe size diago-
nal (those rising from left to right) would be approximately
the best pipe to achieve your goal. To obtain the total
friction loss due to pipe length, multiply the loss figure from
the y (vertical) axis of Figure 15 by the approximate number
of 100-ft lengths of pipe to be installed.
In the sample house, the flow at 2 in. WC is estimated to
be about 9 cfm. From Figure 15 on page 30, to keep the
friction loss between 0.2 and 0.4 in. WC per 100 ft of pipe, 2
in. PVC would be recommended.
The friction loss in straight pipes is only part of the loss
of suction that is experienced in a system. The next most
significant friction loss comes from the bends or tees in the
system. A 90-degree elbow or tee in a pipe usually contrib-
utes the greatest pressure drop. A 45-degree elbow has slightly
more than half the friction loss of a 90-degree elbow, and a
30-degree elbow has less than half that of a 90-degree elbow.
Table 3 on page 29 lists the approximate length of pipe that
will produce the same friction loss as each connector.
To determine the friction loss in inches of water column
(in. WC) for a system:
1. Determine the total length of pipe and the
number and kinds of fittings for each pipe size.
2. Multiply the number of fittings for a pipe size
by the equivalency from Table 3 for that fitting
and pipe.
3. Add the total equivalent feet determined above
to the actual length of pipe to be used to get the
adjusted total length of pipe.
4. Use the friction loss factor determined from
Figure 15 to multiply by that adjusted total.
5. Divide by 100 to get die friction loss for that
size pipe.
6. Repeat the calculation for each pipe size and
add the total together for the whole system.
EXAMPLE: In the sample house, suppose 9 ft of 2 in.
PVC is used at each suction hole, and there are two 30-
degree elbows and one 90-degree elbow in the 2 in.
pipe. The two 30-degree elbows contribute 2 x 0.75 = 1.5 ft
equivalent run of 2 in. PVC, and the 90-degree elbow con-
tributes 1.5 ft of run. These add to 3 ft of equivalent run,
plus the 9 ft of actual pipe, to yidd 12 ft of 2 in. PVC. The
friction loss factor for 2 in. PVC from Figure 15 is 0.25 in.
WC/100 ft. So the total friction loss for the 2 in. pipe is 0.25
x 12/100 = 0.03 in. WC.
Add to that 40 ft of 3 in. PVC and two tees to be used in
the attic from each suction hole. Assume the airflow in the
attic pipe averages about 18 cfm because of the multiple
suction holes. The two tees in the 3 in. pipe are equivalent to
2 x 3 = 6 ft of 3 in. PVC. This; added to the 40 ft of pipe
yields 46 ft. Multiplying this by the 0.1 in. WC/100 ft
friction loss factor from Figure 15 and dividing by 100 yields
46 x 0.1/100 = 0.03 (from 2 in. pipe) + 0.046 = 0.076 in. WC
friction loss in the system.
If this total were far above ithe range mentioned earlier
(0.2-0.4 in. WC), then larger pips size should be considered
27
-------
Conduct sub-slab permeability
diagnostic test.
Collect fan Information from
available manufacturers.
Plot sub-slab flow curve and various fan curves on the same
axis.
Where the sub-slab curve and each fan curve Intersects
indicates approximately the possible operating pressure
differential and resulting airflow.
Determine durability
likelihood.
Estimate
approximate
purchase and
operating costs.
Consider noise
levels (keeping In
mind fan placement
and possible higher
installation costs if
soundproofing).
Consider wiring
requirements
(costs) and other
installation factors.
Decide on the fan which seems to best suit the sub-slab characteristics
and falls within the costs and other requirements of the owner.
Figure 14. Decision process for fan/blower selection.
28
-------
and calculated. Since this value is well below the target
maximum range, this is an acceptable friction load loss.
A word of caution about shopping for PVC pipe is in
order, based on experience. The thinnest walled PVC pipe is
usually adequate and preferred for its weight, ease of cutting,
and cost However, some of the fittings and couplings for
one thickness of pipe (schedule) will not fit properly or
tightly on the same size pipe of a different thickness.
Therefore, make sure there is an adequate supply of
fittings and accessories available for the size and thickness of
the PVC pipe selected.
Table 3. Approximate Friction Loss Equivalencies for Various
Pipe Fittings
Pipe diameter (in.)
1.5
Type of Fitting
Equivalent Run of Pipe (ft)
Tee
90° Elbow
45° Elbow
30° Elbow
1.5
1
0.75
O.S
2
1.5
1
0.75
3
2
1.5
1
5
3
2
1.5
29
-------
10
O
w
3
I
•c
LJ_
0.1 -
0.01
10
Airflow (cfm)
100
Figure 15. Friction chart for average pipes. (Adapted from data presented In the American Society of Heating, Refrigerating and
Alr-Condltlonlng Engineers, Inc. ASHRAE Handbook 1989 Fundamentals, chapter 32.)
30
-------
Section 5
Installing the System
Before any installation is started, it is important to deter-
mine whether any wiring or building modification permits
are required by local (city or county) building officials.
Obtaining these permits and/or scheduling any related in-
spections are necessary steps in the installation procedure.
The costs of such permits and/or inspections should be con-
sidered when making estimates.
Selecting the Specific Center for Drilling
Selecting the exact location for the suction hole is criti-
cal. It must be carefully aligned with other house features
and must simultaneously meet with the homeowner's wishes.
Whatever is found below the slab (pipes, ducts, lines, etc.)
must be dealt with; so must whatever is directly overhead.
Remember, your goal is to run the pipes between the
joists that support the structure overhead. The size of pipes
will directly affect what you choose as the exhaust route.
When you have selected the general location of the
suction hole, and the slab area is exposed to the degree
possible, drill a small hole into the overhead directly above
the optimum placement with as long a bit as is available.
Have another team member in the space above locate the
penetration and determine the feasibility of having a pipe
come through that location. Move this pipe center until it is
satisfactory both from above and from below.
From there, use a plumb bob to mark the exact center for
the suction hole. If the overhead and the slab requirements
cannot be exactly aligned, you may want to use a lateral
displacement with two 30-degree or 45-degree elbows just
above the slab.
Drilling the Slab Hole
Generally, a 5-in. diameter or larger hole is drilled or
cored through the slab. This size is required even if small
pipe is going to be used because of the need to excavate
some of the sub-slab fill material. You may choose to break
out a much larger hole, excavate, and later pour concrete to
restore the slab.
In an unfinished basement, garage, or other unfinished
space, a water-cooled core drill may be used to open a hole
where pouring new concrete will not be necessary. In a
finished living space, you may use a rotary hammer drill to
drill several small holes and then chisel out the larger hole.
A dry core drill is a neat, relatively quick option, but a little
more expensive.
Safety is important when drilling in concrete. The pro-
cess of puncturing a concrete slab is going to produce either
dust (dry methods) or slurry (wet method), so a vacuum
cleaner should be kept running as near to the drilling location
as possible.
If dust is the contaminant, then the vacuum exhaust
should be routed outdoors as far from the house as possible.
Be sure to wear some type of filtering mask when breathing
in this dusty environment. Once the slab is penetrated, wear
a respirator designed for radionuclides and radon decay prod-
ucts, because of the potential for contamination by high
concentrations of radon and radon decay products in the soil
gas. You should also wear some type of sound suppressor
while drilling.
Take care to contain the drill to just through the slab.
Pipes, sometimes PVC as well ais metal, may be found under
the slab in places you would least expect to find them.
Excavating the Suction Pits
The biggest problem with SSD systems in low-perme-
ability soils is the difficulty to extend the pressure field.
Theoretically, the larger you could dig a pit from which to
take the suction, the greater would be the potential for a
better pressure field extension. However, there is a practical
limit to how much soil you can remove from under the
suction hole.
The physical process of excavating soil from under an
existing slab, through a limited access hole, often makes the
removal of 12 to 20 gal. of soil a reasonable target. Opening
another hole is a better option than expanding a single hole
much larger than this.
Research also indicates a wide shallow hole is usually
more effective than a deep narrow hole of the same volume.
Exceptions to this include the case in which the upper layer
of soil has been well compacted and a deeper hole may
penetrate a more permeable layer if the radon entering the
house is coming from that layer. A deep pit is also desirable
if the system is to span an interior footing or a sunken slab
area.
The pit for a suction hole near a stem wall should be dug
toward the interior of the house,. Too much exposure of the
stem wall may result in suction head loss through porous
blocks or penetrations.
Finishing the Suction Hole
If you remove a large portion of slab to excavate a pit,
remember to leave a lip of undisturbed soil wide enough to
help support the weight of restored concrete. Place a sheet of
31
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pressure-treated plywood or sheet metal with a PVC flange
at the suction point on that lip of soil.
Fasten the PVC exhaust pipe to the flange, and pour
concrete on top of the supporting sheet, around the pipe,
flush with the existing slab. The choice of plywood or sheet
metal should be determined according to local code specifi-
cations, including, but not limited to, termite requirements.
If you do not remove a large section of slab, but drill or
core a 5-in. hole through the slab, you can use some combi-
nation of PVC sleeves, bushings, flanges, and/or reducers to
fill the slab hole and join with the pipe size chosen in
accordance with Section 4. Securely caulk the outermost
piece of hardware into the slab hole, both to provide stability
and to seal any potential leaks. A quality urethane caulk is
recommended.
The remaining hardware components used to reduce the
resulting slab hole to the pipe size should fit quite tightly and
be glued securely to one another to prevent leaks. The
schematic in Figure 16 on page 33 illustrates one such
combination of PVC fittings.
Other Types of Installations
Vertical penetration through the house slab is the most
common type of suction hole installed in an SSD system.
However, you may likely run into situations where another
type of penetration is more practical. These may include
garage installation or exterior installation.
Garage Installation. A suction hole through a house
slab that extends into the garage is just like one in an interior
space. However, it is usually near a stem wall or the edge of
the house slab, so you should dig the pit so as to direct the
pressure field extension toward the interior of the house.
Any suction holes in or near a garage may draw in air
through garage floor/wall cracks or other cracks. Therefore,
you should caulk all large cracks, and check any others that
arc questionable to determine if air is being pulled in and if
so, whether caulking is required.
If the garage slab is not part of the house slab, you may
still place a suction hole in the garage. If the house slab and
the garage slab are separated by a stem wall, then horizontal
penetration through that stem wall may be possible from the
garage. If the vertical displacement between the floor levels
is nol great enough, this process may require removing a
portion of the garage slab and sub-slab fill.
When the garage slab is just a step-down form pour
from the house slab, you may install a suction hole in one of
two ways. The first method is to cut away a section of the
garage slab large enough to sink the PVC pipe with a 90-
dcgrcc elbow and to dig an adequate pit from under the
house slab. Place a piece of sheet metal, through which the
elbow can be scaled, vertically as a barrier between the pit
under the house slab and the soil that will be backfilled into
the garage hole before the garage slab is restored. Figure 17
on page 34 illustrates this type of installation.
The second possibility is to drill through a garage/house
slab interface on a 45- degree angle. The resulting core hole
is usually longer and more difficult to excavate, but the
finishing steps are a bit simpler than having to restore part of
the garage slab. Figure 18 on page 35 illustrates this type of
hole and pit.
Exterior Installation. If interior suction holes are not
practical, and if access to the stem wall beneath the slab in
necessary locations can be reached easily from outside the
house, then a horizontal penetration through that stem wall is
a good alternative.
Once the sub-slab space is entered, the horizontal pits
are dug similar to vertical ones. The greatest effort is to
extend the pit as far toward the slab area to be mitigated as
possible. Leaving as much undisturbed fill material along
the stem wall as possible will help reduce any leakage or
short-circuiting through that wall. The schematic in Figure
19 on page 36 illustrates some of the installation details.
Piping Layout and Fan Placement
Before installing the fan, check to see whether you will
need an electrical permit for wiring, especially if you plan to
use a separate branch and breaker.
Attic Piping. It is a good idea to spend a little extra time
planning for the piping runs rather than wasting time, effort,
and materials putting together a less attractive, less effective
system. Keys to planning the piping layout include:
Minimizing total length of pipe runs
Minimizing number of bends
Using 30-degree or 45-degree bends rather than
90-degree bends where possible
Locating the fan at the optimum placement for
the homeowner's desires and the effectiveness
of the system
Sloping the pipe downward from the fan to
allow any condensation to flow back
into suction holes (This helps avoid in-line
airflow blockage.)
Generally a trunk line type of arrangement will incorpo-
rate these features and conform to the overall layout of the
attic as well. If several suction lines feed into a central trunk
line, the trunk may need to have a larger diameter than pipes
coming from the individual suction holes. Figure 20 on page
37 shows the attic piping diagram for the sample house.
To keep the slopes favorable and the pipe less conspicu-
ous, start the pipe run from the suction holes at the tops of
the ceiling joists, and run them to the trunk line. Since the
trunk line needs,to be above the tops of the ceiling joists and
rising gradually, you may rest it on a truss for support. If
trusses are not available, suspend straps from a rafter to keep
the pipe from sagging. In all cases where the pipe touches
wood or other materials, use padding to reduce possible
vibration and noise.
, If more than one trunk line is used, it is necessary for
their intersection to be level so there is no low spot in one of
the lines. Since the trunk lines usually intersect just below
where the fan will be installed, you may want to place blocks
32
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1.5- to 3-in. PVC pipe to attic fan.
All PVC joints and junctions must
be glued tightly
4-in. PVC pipe or sleeve
Urethane caulk for an airtight seal
PVC collar
\
Excavate as large a pit as possible
(12 - 20 gal.) under the slab
.A v, ^,.
Figure 16. "'«»«««Mi o|'•^yplcal Interior suction point showing the 4- to 5-in. hole drilled through the slab, the 12- to 20-gal. pit
«*e attte!^ 8 8ampllnfl pf PVCcoHa'*' «'«»ves, reducers, etc., leading to the exhaust pipe going Into
33
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To attic vent piping system and fan
Seal interface between new
concrete and pipe with flowable
urethane or other flexible sealant
House slab
\
\
New concrete slab over 6 mil or
greater poly vapor barrier (concrete
thickness to match existing slab)
Clean cut thoroughly and apply
/even coat of epoxy adhesive before
' installing new concrete
-^AN,V
K>>
w.
K
Os^
•^Existing fill or native soil
Refill cavity under garage slab with
previous fill material
Leave pit open
under the house slab
Sheet metal or other acceptable soil
barrier
Raure 17. Illustration of a garage suction pipe horizontal Installation Into a pit under the house slab in a house where the garage
slab Is a step-down form pour from the house slab. If the house and garage slabs are separated by a stem wall, then the
pipe goes In through that wall rather than the sheet metal as pictured here.
34
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To attic vent piping system and fan
Dig as large a pit as possible (12 -
20 gallons) from under the house
slab
House slab
^*&&&
Caulk thoroughly the pipe/slab
.interface
^Garage slab
Figure 18. Illustration of a garage suction pipe 45° Installation to a pit under the house slab in a house where the garage slab is a
step-down form pour from the house slab.
35
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Exhaust pipe Is routed up the side
of the house, around the eaves,
above the roof line, and away from
windows or doors that may be left
open.
Reducer/couplers may be
necessary depending on the fan
and pipe sizes..
. Mitigation fan must be rated and
wired for exterior applications.
Liberal quantities of urethane caulk
should be used to prevent any
leakage around the pipe.
v f ^^L ' v v
NN^.vSSs.NS
Figure 19. Exterior suction hole detail showing the horizontal hole through the stem wall, the 12- to 20-gal. suction pit, and the
exterior-mounted mitigation fan. Multiple exterior suction holes may be routed to the same fan.
36
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Attic Access
Fan
Figure 20. Attic piping layout for the sample house plan of Figure 1.
37
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or other supports under that point to prevent a depression
there.
Attic Fan Placement. If using a quiet in-line centrifu-
gal fan, try to locate it near a central point in the piping
system to reduce the longest piping runs. If using one of the
noisier fans, try to locate it over a garage or somewhere as
far from bedrooms as possible.
Other considerations for fan placement include the need
to run power to the fan, and the ease of being able to reach
the fan to repair or replace it. Also, in attics with fairly
limited vertical room, the fan will need to be placed with
adequate space above and below. This usually places it near
the roof peak. Most homeowners will probably want the
stack on the back side of the peak.
Roof Penetrations. SSD systems that run through the
attic will need a roof penetration for the exhaust stack to exit.
If using an in-line centrifugal fan with an exhaust port larger
than 4 in., you should use a reducing coupler, usually made
of neoprene-like material, to get down to a 4-in. diameter
exhaust pipe. More powerful fans usually already have a
small diameter exhaust port. The exhaust pipe for them
should be of equal or slightly larger diameter than the port.
The exact exit point must be carefully determined. Lo-
cate the vent stack near the center of the roof, as far from any
air inlet as possible. The stack should be high enough to
escape all building down wash effects in order to avoid
reentry of contaminated soil gas into the house. Also, be
sure to follow local codes covering roof penetrations.
Use some type of roof flashing (usually lead or neo-
prene) that will fit snugly around the pipe. The flashing
must be flexible enough to accommodate movement of the
pipe and any misalignment caused by either installation error
or nonstandard pitch of the roof.
Be careful to blend the flashing into the shingles to
prevent any water leaks. Place the flashing lip under shingles
on the up-slope side, and over shingles on the down-slope
side. Apply liberal amounts of high-quality roofing tar or
caulk to all areas where shingles have been disturbed.
Finally, place some type of vent cap over the end of the
slack to prevent water from entering the pipes and damaging
the fan. Any kind of stove cap or other device will work, as
long as it allows the free exhaust of air while preventing the
entry of water. Figure 21 on page 39 illustrates the fan
placement and roof penetration in a typical installation.
NOTE: Because SSD systems in low-
permeability fill material produce low air-flows,
using a vent cap is recommended. SSD systems
in higher permeability materials produce higher
airflows, which will deflect water, thereby
reducing the need for a vent cap.
Exterior Piping. In houses with basements, where the
exhaust piping is routed out through a rim joist, or in slab-
on-grade houses, where an exterior suction hole is installed,
the piping and fan will usually be placed outside the house
shell. In these cases, the fan must be rated for exterior
applications, and the wiring must be adequately shielded to
meet all local codes.
In houses with basements, there is usually just one pipe
coming through the wall to the outside. You may need to
run the pipe horizontally for a distance until reaching a
suitable location for the vertical run. Mount the fan shortly
after the turn upward. You may also need to seal the fan to
prevent potential leakage of radon through the fan housing.
In slab-on-grade houses, it is conceivable that suction
holes from four sides of a house could be routed to the same
fan. If one fan is being used for more than a single hole, you
will need to consider the length of pipe runs, number of
bends, homeowner's desires, and terrain of the yard to deter-
mine the best piping and fan placement. Keep in mind the
need for a slightly upward sloping pipe from the suction hole
to the fan is still valid; so the fan cannot be on the lowest
side of the house.
You can often place the pipe that goes from a suction
hole around the house in a shallow trench. The soil provides
good support for the piping in an exterior application; how-
ever, supporting the fan is more of a problem because the
soil may settle, allowing the fan to sink slightly. This could
cause water collection and could possibly reduce the suction
field far from the fan.
For either of these two exterior fan placements, the
exhausts usually go straight up the side of the house and
angle out to go under the eave, similar to the routing of a
downspout for a gutter. The exhaust stack should extend
several feet above the roof at the eave to reduce the possibil-
ity for contaminated soil gas to reenter the house through
windows or other openings. Use some form of strapping for
support at the end of the eave, and place a rain cap at the end
of the pipe.
38
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Vent cap
Roof flashing; blend in shingles
correctly
k
Caulk roof penetration well
Mitigation fan; wire to run
continuously
Glue all PVC joints tightly
' PVC vent pipes to various collector"
pipes (slight slope away from fan)
Figure 21. Schematic of the fan placement and roof penetration of a typical installation.
39
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Section 6
System Indicators and Labeling
A properly installed radon mitigation system is quiet and
unobtrusive. It is easy for the homeowner to forget the
system exists. Therefore, it is helpful to build into the
system a means of checking on it to make sure all parts are
working properly. A monitoring system also ensures the
system will be remembered if the house is sold.
Because an SSD system works by reducing the air pres-
sure underneath the slab, the system pressure is lower than
the indoor house pressure. By installing a pressure differen-
tial gauge that measures the difference between sub-slab and
house pressures, the homeowner can monitor the relative
effectiveness of the system at any time. Typically the pres-
sure tap is made somewhere in the duct. However, this too
can be forgotten over time. An alternative is some type of
system pressure alarm that sounds or lights up if the pressure
difference falls below a preset level. It should be connected
to a separate power source from the system.
It is also important to properly label the various parts of
the system so any worker who may be unfamiliar with radon
or mitigation systems will be alerted not to tamper with the
system. Steps for labeling include:
1. Label the breaker bos; in accordance with
standard electrical safety procedures. The
specific breaker or fuse that powers the
mitigation system should be so marked,
especially if it is on a line with some other
electrical component.
2. Label the pipes or duels as belonging to the
mitigation system, and label the direction of
flow.
3. Label the system alarm or gauge, indicating
what to do if the system appears to fail.
Generally this includes checking the power (list
the fuse or breaker number), checking the fan
(give directions), inspecting the suction hole
locations for pipe or connection damage,
investigating the pipe runs, and contacting a
mitigation professional (list name, address, and
telephone number).
41
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Glossary
AGGREGATE—Stone, crushed stone, or other inert mate-
rial having hard, strong, durable pieces. When used in house
construction, it forms the uppermost surface on which the
slab is poured, just below the vapor barrier.
COMMUNICATION—The degree to which the effects of a
depressurization at some location under a slab are transmit-
ted to other remote locations under the slab. If a depressur-
ized condition of 0.25-1,0 Pa can be extended under all slab
surfaces, there is a high probability that a sub-slab depressur-
ization system can be installed to remediate the entry of soil-
gas borne radon.
DEPRESSURIZATION—In houses, a condition that exists
when the air pressure within a given space (under the slab,
inside the house, etc.) is slightly lower than the air pressure
in a reference location (in the house, outside, etc.). When a
fan draws air from a closed space, it depressurizes the space.
Houses are sometimes depressurized by the buoyant effect of
warm air rising during cold weather, by winds, and by
appliances which exhaust indoor air.
DRY CORE DRILL—An electric-powered drill that usu-
ally can be used like a small jackhammer, a hammer drill, or
a core drill. This type of drill usually does not use cooling
water. Generally, a chisel bit is used in the jackhammer
mode, a screw bit in the hammer drill mode, or a core bit in
the core drill mode.
FAN CURVE—A plot of the airflow a specific fan can
produce with a given amount of pressure drop. When there
is no flow, the fan will exert the maximum suction or pres-
sure it can attain. The maximum airflow the fan can produce
exists when there is no resistance (free-flowing air), and no
pressure drop across the fan. The collection of points repre-
senting the airflow at any intermediate pressure produces the
fan curve for that fan.
FILL SOIL—The soil that has been graded, placed, and
packed directly under where the slab will be poured. Fill soil
may be brought from another site or may be native to the
area. For a stem wall construction, the fill soil is used to
"fill" the space inside the stem walls up to the level at which
the bottom of the slab will be poured. In a monolithic
construction, the fill soil is the soil into which the footings
and onto which the slab will be poured.
MEDIUM—A substance regarded as the means of transmis-
sion of a force or effect (In this booklet, medium refers to
the sub-slab fill material.)
MITIGATION—The act of making less severe; reduction;
relief.
PERMEABILITY—A measure of the ease with which a
fluid (liquid or gas) can flow through a porous medium.
Sub-slab permeability generally refers to the ease with which
soil gas can flow underneath a concrete slab. High perme-
ability facilitates gas movement under the slab, arid hence
generally facilitates the implementation of a sub-slab suction
radon mitigation system.
PRESSURE CONTOUR—A curve that connects all the
points of exactly the same pressure. When sub-slab suction
is imposed at a given place, the, pressure that can be mea-
sured at various points under the slab generally decreases as
the distance from the nearest suction hole increases. The
pressure contour outlines the area within which the suction is
expected to be greater than or equal to the value at the
contour.
PRESSURE FIELD EXTENSION—The extent to which
the sub-slab area is depressurized by the suction applied at
some suction point.
PVC—Polyvinyl Chloride—Synthetic resin producing a
strong plastic material used for pipes, fittings, and other
items. PVC pipe is smooth for low friction loss, and light-
weight for easy handling. Its gluing characteristics are favor-
able for airtight joints. It is the recommended material for
many mitigation applications.
RADON—A naturally occurring, chemically inert, radioac-
tive gas. It is colorless, odorless,, and tasteless. It is part of
the uranium-238 decay series, the direct decay product of
radium-226.
RIM JOIST—The perimeter horizontal timber or beam sup-
porting a floor or a ceiling.
ROTARY HAMMER DRILL—An electric-powered drill
that usually uses solid bits (rather than core bits). Its action
may be a piston-driven action like a lightweight jackhammer
only, or as a drill with the hammer-tike action.
SCALING BASELINE HOLE—A hole within about 12 in.
of a suction test hole (during a diagnostic test) at which a
pressure measurement can be taken. Because during a vacuum
cleaner diagnostic test procedure (he suction is being applied
on a very small volume hole, this is not a fair representation
of what a mitigation system fan would produce. Since
mitigation fans generally do not produce as much suction as
vacuum cleaners, pits are dug to at least 12 in. from the
suction hole. The vacuum cleaner is usually run at a speed
that will produce a depressurization of about 200 Pa at the
scaling baseline hole to simulate the pressure field that would
be produced by a 200 Pa mitigation fan.
43
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SLAB-ON-GRADE—A type of house construction in which
the bottom floor of a house is a concrete layer (typically
about 4 in. thick and in direct contact with the underlying
aggregate or soil) which is no more than 1 ft below grade
level on any side of the house.
STEM WALL—The one or more courses of block (or equiva-
lent height of poured concrete) that is placed above the
buried footings comprising the foundation of the house. If
the slab is poured inside the stem wall, it is considered to be
a "floating" slab. More typically the top course of the stem
wall is an "L" or "chair" block with a 4-in. notch cut through
half of the thickness of the block so that the slab is poured
into the stem wall. Occasionally the slab is poured into
forms that cover the entire top of the stem wall.
SUB-SLAB FLOW CURVE—A graph representing the
functional relationship between the amount of suction ap-
plied on a soil and the flow that results from that suction. If
gravel with large pore spaces is the sub-slab medium, then
just a small suction will generally produce a fairly large
flow; loose sand would produce less flow for the same
suction; a more tightly packed soil would produce even
lower flows for equivalent suction. Therefore, the sub-slab
flow curve would rise more sharply for more permeable
media and more gradually for more tightly packed media.
SUCTION HOLE/POINT—The hole cut into the sub-slab
space from which either a vacuum cleaner (for diagnostic
purposes) or a mitigation fan will evacuate the sub-slab soil
gas.
TRUNK LINE—A main pipe for soil gas movement, usu-
ally in the attic, into which the pipes from the individual
suction holes empty.
VAPOR BARRIER—A product or system designed to limit
the free passage of a gas (typically water vapor) through a
building envelope component (wall, ceiling, or floor). Such
products and systems may be continuous or noncontinuous
discrete elements which are sealed together to form a con-
tinuous barrier against air (or vapor) infiltration (most com-
monly, a plastic sheet under a house slab).
WATER-COOLED CORE DRILL—An electric-powered
heavy drill that can be used to drill cores out of concrete
slabs. Because of the heat produced by the core bit cutting
through the concrete, water is sprayed or dripped onto the bit
while it is cutting in order to keep it cool. The water also
acts as a lubricant between the bit and concrete to some
degree.
44
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Abbreviations
cftn—cubic feet per minute—A measure of the volume of a
fluid (liquid or gas) flowing within a fixed period of time.
Pa—pascal—The SI (System International) unit of pressure,
249.1 Pa =1 in. WC.
pCi/L—picocurie per liter—A common unit of measure-
ment of the concentration of radioactivity in a gas. A
picocurie per liter corresponds to 0.037 radioactive disinte-
grations per second in every liter of air. Also, 1 pCi/L = 37
Bq/m3 (becquerels per cubic meter).
R-1SO/K6—In-line centrifugal fans manufactured by Fantech/
Kanalflakt, respectively.
RDS—Radon Detection Services—An in-line centrifugal
fan developed and/or marketed by the company of the same
name.
WC—water column—A term used to describe air pressure
in hydrostatic terms; i.e., the height (in in., mm) of a column
of water that would exert an <;quivalent pressure to the
pressure being measured.
45
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References
Additional information is available by dialing the na-
tional Radon Hot line number, 1-800-SOS-RADON or 1-
800-767-7236.
Either of the following agencies can provide the publica-
tions listed below.
U.S. Environmental Protection Agency
Office of Research and Development
Center for Environmental Research Information
Cincinnati, OH 45268
Or
National Technical Information Service
U.S. Department of Commerce
5285 Port Royal Road
Springfield, VA 22161
1. Findlay, W. O., A. Robertson, and A. G. Scott. Testing of
Indoor Radon Reduction Techniques in Central Ohio
Houses: Phase 1 (Winter 1987 - 1988X EPA-600/8-89-
071 (NTIS PB89-219984), U.S. Environmental Protection
Agency, Research Triangle Park, NC, 1989. 301 pp.
2. Henschel, D. B. Radon Reduction Techniques for
Detached Houses: Technical Guidance (second edition).
EPA-625/5-87-019 (NTIS PB88-184908), U.S.
Environmental Protection Agency, Cincinnati, OH, 1987.
192 pp.
3. Michaels, L. D., T. Brennan, A. S. Viner, A. Mattes, and
W. Turner. Development and Demonstration of Indoor
Radon Reduction Measures for 10 Homes in Clinton.
New Jersey. EPA-600/8-87-027 (NTIS PB87-215356),
U.S. Environmental Protection Agency, Research
Triangle Park, NC, 1987. 166 pp.
4. Mosley, R. B. and D. B. Henschel. Application of Radon
Reduction Methods (Revised). EPA-625/5-88-024 (NTIS
PB89-205975), U.S. Environmental Protection Agency,
Cincinnati, OH, 1989. 129 pp.
5. Osbome, M. C., T. Brennan, and L. D. Michaels. Radon
Mitigation in 10 Clinton. New Jersey. Houses: A Case
History. EPA-600/D-87-164 (NTIS PB87-191847),U.S.
Environmental Protection Agency, Research Triangle
Park, NC, 1987. 12pp.
6. Pyle, B. E., A. D. Williamson, C. S. Fowler, F. E. Belzer,
M. C. Osborne, and T. Brennan. Radon Mitigation
Techniques in Crawl-Space. Basement, and Combination
Houses in Nashville. Tennessee. In Proceedings: The
1988 Symposium on Radon and Radon Reduction
Technology, Volume 1. EPA-600/9-89-006a (NTIS
PB89-167480), U.S. Environmental Protection Agency,
Research Triangle Park, NC, 1989, 7-51—7-64.
7. Ronca-Battista, M., P. Magno, and P. Nyberg. Interim
Protocols for Screening and Follow-up Radon and Radon
Decay Product Measurements. EPA-520/1 -86-014.1, U.S.
Environmental Protection Agency, Cincinnati, Ohio,
1987. 22pp.
8. Scott, A. G., A. Robertson, and W. O. Findlay. Installation
and Testing of Indoor Radon Reduction Techniques in
40 Eastern Pennsylvania Houses. EPA-600/8-88-002
(NTIS PB88-156617), U.S. Environmental Protection
Agency, Research Triangle Park, NC, 1988. 388 pp.
9. Scott, A. G., and W. O. Findlay. Demonstration of
Remedial Techniques against Radon in Houses on Florida
Phosphate Lands. EPA-520/5-83-009 (NTIS PB84-
156157), U.S. Environmental Protection Agency,
Montgomery, AL, 1983. 180 pp.
10. Turk, B. H., J. Harrison, R. J. Prill, and R. G. Sextro.
Preliminary Diagnostic Procedures for Radon Control.
EPA-600/8-88-084 (NTIS PB88-225115), U.S.
Environmental Protection Agency, Research Triangle
Park, NC, 1987. 58 pp.
11. U.S. Environmental Protection Agency. A Citizen's
Guide to Radon. OPA-86-004, Washington, DC, 1986.
13 pp.
12. U.S. Environmental Protection Agency. Indoor Radon
and Radon Decay Product Measurement Protocols. EPA-
520-1/89-009 (NTIS PB89-224273), Washington, DC,
1989. 102pp.
Other publications which provide information about ra-
don mitigation include:
Practical Radon Control for Homes. Terry Brennan and
Susan Galbraith, Cutter Information Corporation, 1989.
163pp.
Radon and Its Decay Products in Indoor Air. Eds. William
W. Nazaroff and Anthony V. Nero, Jr., Environmental
Science and Technology Service, 1988. 518 pp.
47
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Radon: Risk and Remedy. David J. Brenner, W. H. Freeman,
1989. 228pp.
Reducing Radon in Structures. U.S. EPA, Office of Radiation
Programs, Washington, DC 20460. Information about
the current version being used in each of the Regional
Training Centers is available from that center listed in
the following section.
The Radon Industry Directory. Radon Press, Inc. (Annual
Edition) 540+ pp.
Radon Product and Service Guide. Solaplexus Publications
Division. (Annual Edition).
Further information about ventilation systems and duct-
ing is available from:
ASHRAE Handbook 1989^ Fundamentals. American Society
of Heating, Refrigerating and Air-Conditioning Engineers,
Inc., chapter 32.
48
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Regional Training Centers
Eastern Regional Radon Training Center
Rutgers University
Cook College, Radiation Science
Kilmer Campus, Building 4087
New Brunswick, NJ 08903
(201) 932-2551 (201) 932-2582
Midwest Universities Radon Consortium,
University of Minnesota
Minnesota Extension Service
1985 Buford Avenue (240)
St. Paul, MN 55108-1011
(612) 625-5767
Western Regional Radon Training Center
Colorado State University
Guggenheim Hall
Department of Radiology and Radiation Biology
Fort Collins, CO 80523
(303)491-5205
Southern Regional Radon Training Center
Department of Civil Engineering
238 Harbert Engineering Center
Auburn University
Auburn, AL 36849-5337
(205) 844-6261
•&U.S. GOVERNMENT PRINTING OFFICE: 1992 - £48-003/60055
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