v>EPA
United States
Environmental Protection
Agency
Air And
Radiation
(6604J)
EPA 4eg-R-93-QQa-
June 1993
Protocols For Radon And
Radon Decay Product
Measurements In Homes
\
Printed on Recycled Paper
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Preface
This document, the Protocols for Radon and Radon Decay Product
Measurements in Homes (EPA 402-R-92-003, May 1993), is a guidance
document. However, one condition of participation in the Agency's National
Radon Measurement Proficiency Programs for radon measurement and radon
reduction (mitigation) proficiency, is conformance with these protocols.
Conformance with its companion document, the Indoor Radon and Radon
Decay Product Measurement Device Protocols (EPA 402-R-92-004, July 1992),
is also a condition of participation in the Proficiency Programs.
Together these protocol documents provide the technical support for the
Agency's radon policy and guidance to consumers that is contained in, but not
limited to, the Home Buyer's and Seller's Guide to Radon (EPA 402-R-93-003,
March 1993), A Citizen's Guide to Radon (EPA 402-K-92-001), and the
Consumer's Guide to Radon Reduction (EPA 402-K-92-003, August 1992).
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CONTENTS
Section
List of Exhibits v
Section 1: INTRODUCTION 1.1
Section 2: DISCUSSION OF GUIDELINES PRESENTED IN THE
CITIZEN'S GUIDE TO RADON
2.1 Introduction and Summary 2-1
2.2 Measurement Location 2-3
2.3 Initial Measurements
2.3.1 Rationale 2-4
2.3.2 Closed-Building Conditions ... 2-5
2.3.3 Interpretation of Initial Measurement Results 2-6
2.4 Follow-Up Measurements
2.4.1 Rationale 2-7
2.4.2 Short-Term and Long-Term Follow-Up Testing 2-7
Section 3: DISCUSSION OF GUIDELINES PRESENTED IN THE HOME BUYER'S
AND SELLER'S GUIDE TO RADON
3.1 Introduction 3_1
3.2 Options for Real Estate Testing
3.2.1 Option 1: Sequential Testing 3.4
3.2.2 Option 2: Simultaneous Testing 3.4
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3.2.2.1 Both Measurement Results Equal To or Greater
Than 4 pCI/L 3-4
3.2.2.2 Both Measurement Results Less Than 4 pCi/L 3-6
3.2.2.3 One Measurement Result Greater Than 4 pCi/L,
and One Measurement Result Less Than 4 pCi/L 3-6
3.2.2.4 Precision Requirements 3-6
3.2.2.5 Recommended Language for Informing the
Client that a Retest is Warranted 3-7
3.2.3 Option 3: Active Monitor Testing 3-7
3.3 Measurement Location 3-8
3.4 Measurement Checklist 3-9
3.5 Interference-Resistant Testing 3-10
3.5.1 Influencing Test Area Concentration 3-11
3.5.2 Equipment Interference 3-12
3.5.3 Preventing Interference 3-12
3.5.4 Interference-Resistant Detectors 3-13
Section* GENERAL PROCEDURAL RECOMMENDATIONS
4.1 Introduction 4-1
4.2 Initial Client Interview 4-1
4.3 Measurement Recommendations
4.3.1 Selecting a Measurement Approach 4-1
4.3.2 Written Measurement Guidance 4-2
4.3.3 Conditions for a Valid Measurement 4-3
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4.3.4 Non-interference Controls 4-3
4.3.5 Measurement Documentation 4-4
4.4 Quality Assurance in Radon Testing 4-5
4.4.1 Calibration Measurements 4-5
4.4.2 Known Exposure Measurements 4-5
4.4.3 Background Measurements 4-6
4.4.4 Duplicate Measurements 4-7
4.4.5 Routine instrument Performance Checks 4-7
4.4.6 Quality Assurance Plans 4-7
4.5 Standard Operating Procedures 4-8
4.6 Providing Information to Consumers 4-8
4.7 Reporting Test Results 4-9
4.8 Temporary Risk Reduction Measures 4-10
4.9 Recommendations for Mitigation 4-10
4.10 Worker Safety 4-10
Appendix A: STATE AND EPA REGIONAL RADON OFFICES
A.1 State Radiation and Radon Offices A-1
A.2 EPA Regional Radiation (Radon) Program Managers A-7
Appendix B: INTERPRETATION OF THE RESULTS OF SIMULTANEOUS
MEASUREMENTS
B.1 Assessment of Precision B-1
B.2 Example Control Charts for Precision B-2
iii
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B.2.1 Sequential Control Chart Based
on Coefficient of Variation B-3
B.2.2 Sequential Control Chart Based on
Relative Percent Difference B-4
B.2.3 Range Control Chart B-8
B.3" Interpretation of Precision Control Chart B-10
Glossary
G-1
References
R-1
IV
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LIST OF EXHIBITS
Exhibit Number and Title
1-1 EPA Documents Providing Guidance on Radon Measurements 1-2
1-2 Radon and Radon Decay Product Measurement Method Abbreviations 1-4
2-1 Recommended Testing Strategy for Determining the Need for
Mitigation in Homes 2-2
3-1 Radon and Radon Decay Product Measurement Method Categories 3-3
3-2 Deciding on a Retest When Measurements Vary Significantly 3-5
A-1 Map of EPA Regions A-8
B-1 Control Chart for Coefficient of Variation Based on an
"In Control" Level of 10 Percent B-5
B-2 Control Chart for Relative Percent Difference Based on an
"In Control" Level of 14 Percent B-6
B-3 Control Chart for Relative Percent Difference Based on an
"In Control" Level of 25 Percent B-7
B-4 Range Control Chart to Evaluate Precision B-9
B-5 Criteria for Taking Action for Measurements Outside
the Warning Level B-11
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Section 1: INTRODUCTION
This document presents the U.S. Environmental Protection Agency's (EPA)
technical guidance for measuring radon* concentrations in residences. It contains
protocols for measuring radon for the purpose of deciding on the need for remedial
action, as presented in the 1992 Citizen's Guide to Radon (EPA 402-K-92-001; U.S.
EPA 1992a), and in the Home Buyer's and Seller's Guide to Radon (EPA 402-R-93-
003; U.S. EPA 1993).
The guidance for determining the need for mitigation is different in several key
aspects from previously issued recommendations, and this document supersedes a
previous report (EPA 520/1-86-014-1) published in February, 1987 (U.S. EPA 1987).
The technical basis for these policy changes is supplied in the Technical Support
Document for the 1992 Citizen's Guide to Radon (EPA 400-R-92-011; U.S.
EPA 1992g), and the revised policies are described in Section 2 of this report.
Section 3 of this report describes the Agency's recommended protocols for
measuring radon for a real estate transaction. This guidance elaborates on Agency
recommendations published in the Home Buyer's and Seller's Guide to Radon (EPA
402-R-93-003; U.S. EPA 1993). The radon testing guidelines in the Home Buyer's
Guide were developed specifically to deal with the time-sensitive nature of home
purchases and sales and the potential for radon device interference. The guidelines
are somewhat different from those in other EPA publications, such as the 1992
Citizen's Guide to Radon (EPA 402-K-92-001; U.S. EPA 1992a), which provide radon
testing and reduction information for non-real estate situations. Therefore, Sections 2
and 3 of this document will have different guidance for different situations.
This report is limited to discussions of Agency guidance regarding detector
placement, measurement duration, multiple measurements, and the interpretation of
measurement results. EPA has also issued a technical report describing
measurement techniques, titled Indoor Radon and Radon Decay Product
Measurement Device Protocols (EPA 520-402-R-92-004) and published in 1992 (U.S.
EPA 1992c). That report provides technical information for measuring radon
concentrations with continuous radon monitors, alpha track detectors, electret ion
chambers, charcoal canisters, unfiltered alpha track detectors, and grab radon
techniques; it also provides guidance for measuring radon decay product
concentrations with continuous working level monitors, radon progeny integrating
sampling units, and grab radon decay product techniques. Copies of the Indoor
Radon and Radon Decay Product Measurement Device Protocols may be obtained
by contacting your State or EPA Regional radon office (Appendix A). A list of EPA
documents providing guidance on radon measurements appears in Exhibit 1-1.
* The term "radon" refers to radon-222 and its decay products unless otherwise noted.
1-1
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Exhibit 1-1
EPA Documents* Providing Guidance on Radon Measurements
Title of Document
A Citizen's Guide to Radon
(U.S. EPA 1992a)
Consumer's Guide to Radon Reduction
(U.S. EPA 1992b)
Indoor Radon and Radon Decay Product
Measurement Device Protocols
(U.S. EPA 1992c)
Interim Radon Mitigation Standards
(U.S. EPA 1992d)
Home Buyer's and Seller's Guide to Radon
(U.S. EPA 1993)
Protocols for Radon and Radon Decay Product
Measurements in Homes
EPA Document Number
EPA 402-K-92-001
EPA 402-K-92-003
EPA 520-402-R-92-004
Regional Training Centers
(see below)
EPA 402-R-93-003
EPA 402-R-92-003
These documents are available from the U.S. Government Printing Office
Superintendent of Documents, Mail Stop: SSOP, Washington, D.C. 20402-
9328; from the National Technical Information Service, U.S. Department of
Commerce, Springfield, Virginia 22151; or your State or EPA Regional radon
office.
EPA Regional Radon Training Centers-
Eastern Regional Radon Training Center, Rutgers University; (908)-932-2582.
Southern Regional Radon Training Center, Auburn University; (205)-844-6271.
Western Regional Radon Training Center, Colorado State University (303)-
491-7742. '
Northern Regional Radon Training Center, University of Minnesota; (612)-624-
6786.
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This report provides guidelines that are primarily intended to aid State radiation
control programs, other organizations conducting indoor radon measurements, and
homeowners who want detailed information on radon measurements. The guidelines
herein can be adopted as part of a State program or can be provided by States to
interested individuals as recommendations. Adherence to these guidelines is a
requirement for participation in the National Radon Measurement Proficiency (RMP)
Program (EPA 520/1-91-006; U.S. EPA 1991). The method designations used in the
RMP Program are listed in Exhibit 1-2. A two-letter code for each method has been
adopted, although ATDs (AT), RPISUs (RP), and EiCs/ECs (ES or EL) may still be
referred to by their traditional acronyms.
EPA recognizes that radon concentrations in buildings may vary over time (Arvela
el aj- 1988, Dudney et a|. 1990, Fleischer and Turner 1984, Furrer et aJL 1991, Gesell
1983, Harley 1991, Hess 1985, Martzet a[. 1991, Nyberg and Bemhardt 1983, Perritt
et a}. 1990, Ronca-Battista and Magno 1988, Steck 1992, Stranden et a]. 1979,
Wilkening and Wicke 1986, Wilson งt a]. 1991). Furthermore, concentrations at
different locations in the same house often vary by a factor of two or more (Arvela iet
a]. 1988, Furrer et a]. 1991, George et M-1984, Hess 1985, Keller et aj. 1984, Put and
deMeijer 1988, Steck 1992). EPA has carefully evaluated these findings, as well as
other factors (EPA 400-R-92-011; U.S. EPA 1992g), and has developed policies for
ensuring that the most representative and useful information is supplied by the
measurement results. These guidelines may be evaluated periodically and refined to
reflect the increasing knowledge of, and experience with, indoor radon. ,
EPA recommends that initial measurements be short-term tests performed under
closed-building conditions. An initial short-term test, which lasts for two to 90 days,
ensures that residents are informed quickly should a home contain very high radon
levels. Long-term tests give a better estimate of the year-round average radon level.
The closer the long-term test is to 365 days, the more representative it will be of
annual average radon levels.
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Exhibit 1-2
Radon and Radon Decay Product Measurement Method Abbreviations
I METHOD CATEGORY
Continuous Radon Monitors
Alpha Track Detectors
Electret Ion Chambers
Short Term
Long Term
Activated Charcoal Adsorption Devices
(formerly called charcoal canisters)
Charcoal Liquid Scintillation
I Three-day Integrating Evacuated Scintillation Cells
| Pump/Collapsible Bag Devices
I (24 hour samplej
I Grab Radon Sampling
Scintillation Cells
Activated Charcoal
Pump-Collapsible Bag
Unfiltered Track Detectors
Continuous Working Level Monitors
Radon Progeny Integrating Sampling Units
Grab Sampling - Working Level
Abbreviations
Common
CRM
ATD
EIC/EC
CC
CLS
UTD
CWLM
RPISU
RMP
Method
CR
AT
ES
EL
AC
LS
SC
PB
GS
GC
GB
UT
CW
RP
GW
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Section 2: DISCUSSION OF GUIDELINES PRESENTED IN
THE CITIZEN'S GUIDE TO RADON
2.1 INTRODUCTION AND SUMMARY
The Citizen's Guide to Radon (EPA 402-K-92-001; U.S. EPA 1992a) presents a
measurement strategy for assessing radon levels in homes for the purpose of
determining the need for remedial action. This measurement strategy is intended to
reduce the risk to public health from exposure to radon in air in homes. The strategy
begins with an initial measurement made to determine whether a home may contain
radon concentrations sufficient to cause high exposures to its occupants.
EPA recommends that initial measurements be short-term tests placed in the
lowest lived-in level of the home, and performed under closed-building conditions. An
initial short-term test ensures that residents are informed quickly should a home
contain very high levels of radon. Short-term tests are conducted for two days to 90
days. Closed-building conditions (Section 2.3.2) should be initiated at least 12 hours
prior to testing for measurements lasting less than four days, and are recommended
prior to tests lasting up to a week.
If the short-term measurement result is equal to or greater than 4 picocuries per
liter (pCi/L), or 0.02 working levels (WL), a follow-up measurement is recommended.
Follow-up measurements are conducted to confirm that radon levels are high enough
to warrant mitigation. If the result of the initial measurement is below 4 pCi/L, or 0.02
WL, a follow-up test is not necessary. However, since radon levels change over time,
the homeowner may want to test again sometime in the future, especially if living
patterns change and a lower level of the house becomes occupied or used regularly.
There are two types of follow-up measurements that may be conducted, and the
choice depends, in part, on the results of the initial test: An initial measurement result
of 10 pCi/L (or 0.05 WL) or greater should be followed by a second short-term test
under closed-building conditions. If the result of the initial measurement is between 4
pCi/L (or 0.02 WL) and 10 pCi/L (or 0.05 WL), the follow-up test may be made with
either a short-term or a long-term method. Long-term tests are conducted for longer
than 90 days, and give a better estimate of the year-round average radon level. The
closer the long-term measurement is to 365 days, the more representative it will be of
annual average radon levels. On the other hand, short-term tests yield results more
quickly and can be used to make mitigation decisions. If the long-term follow-up test
result is 4 pCi/L, or 0.02 WL, or higher, EPA recommends remedial action. If the
average of the initial and second short-term results is equal to or greater than 4 pCi/L,
or 0.02 WL, radon mitigation is recommended. These recommendations are
summarized in Exhibit 2-1.
2-1
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Exhibit 2-1
Recommended Testing Strategy for
Determining the Need for Mitigation in Homes
Perform initial short-term radon measurement
* or 0.02 WL
* or 0.05 WL
If the result is
> 10 pOi/L**
or results
are needed
quickly
If the result
is>4pCi/L*
but
< 10 pCi/L
If the result
is<4pCi/L*
A follow-up test is
not necessary now
Consider testing
again in the
future, however,
and if a lower
level (basement)
becomes more
frequently used,
test there.
Perform a
short-term or
a long-term
follow-up
measurement
A short-term
follow-up
measurement
is
performed
Average the
results of the
initial arid
follow-up
short-term
measurements
A long-term
follow-up
measurement
is
performed
Is this
result
< 4 pCi/L* ?
Even if the test
result is < 4 pCi/L,*
consider testing
again sometime in
the future.
Remedial Action
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In certain instances, such as may occur when measurements are performed in
different-seasons or under different weather conditions, the initial and follow-up tests
may vary by a considerable amount. Radon levels can vary significantly between
seasons, so different values are to be expected. The average of the two short-term
test results can be used to determine the need for remedial action.
The testing strategy policies presented here allow homeowners to decide on the
need for mitigation with a high level of confidence that their decision is correct (EPA
400-R-92-011; U.S. EPA 1992g).
2.2 MEASUREMENT LOCATION
Short-term or long-term measurements should be made in the lowest lived-in
level of the house. The following criteria should be used to select the location of the
detectors within a room on this level:
ii The measurements should be made in the lowest level which contains
a room that is used regularly. Test areas include family rooms, living
rooms, dens, playrooms, and bedrooms. A bedroom on the lower
level may be a good choice, because most people generally spend
more time in their bedrooms than in any other room in the house
(Chapin 1974, Moeller and Underhill 1976, Szalai 1972). If there are
children in the home, it may be appropriate to measure the radon
concentration in their bedrooms or in other areas where they spend a
lot of time, such as a playroom, that are situated in the lowest levels of
the home.
In general, measurements should not be made in kitchens, laundry
rooms, or bathrooms. The measurements should not be made in a
kitchen because of the likelihood that an exhaust fan system and
changes in small, airborne particles (caused by cooking) may affect
the stability of WL measurements. Measurements should not be made
in a bathroom because relatively little time is spent in a bathroom,
because high humidities may affect the sensitivity of some detectors,
and because of the likelihood that use of a fan may temporarily alter
radon or decay product levels.
Although radon in water may be a contributor to the concentration of
airborne radon, radon in air should be measured before any diagnostic
radon-in-water measurements are made. (Diagnostic measurements may
be made in the bathroom; however, such diagnostic measurements should
not be used to determine the need for mitigation.)
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A position should be selected where the detector will not be disturbed
during the measurement period and where there is adequate room for the
device.
The measurement should not be made near drafts caused by heating,
ventilating and air conditioning vents, doors, fans, and windows. Locations
near heat, such as on appliances, near fireplaces or in direct sunlight, and
areas of high humidity should be avoided.
Because some detectors are sensitive to increased air motion, fans should
not be operated in the test area. Forced air heating or cooling systems
should not have the fan operating continuously unless it is a permanent
setting.
The measurement location should not be within 90 centimeters (three
feet) of the doors and windows or other potential openings to the
outdoors. If there are no doors or windows to the outdoors, the
measurement should not be within 30 centimeters (one foot) of the
exterior wall of the building.
The detector should be at least 50 centimeters (20 inches) from the floor,
and at least 10 centimeters (four inches) from other objects. For those
detectors that may be suspended, an optimal height is in the general
breathing zone, such as two to 2.5 meters (about six to eight feet) from the
floor.
Sound judgement is required as to what space actually constitutes a room.
Measurements made in closets, cupboards, sumps, crawl spaces, or nooks within the
foundation should not be used as a representative measurement.
2.3 INITIAL MEASUREMENTS
2.3.1 Rationale
EPA recommends that a homeowner assessing the need for mitigation should first
make a short-term test. Short-term measurements can be simple, produce results
quickly, and allow the public to make decisions about radon reduction that are
cost-effective and protective of human health.
The duration of short-term measurements can range from 48 hours to 90 days,
depending upon the method used.
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2.3.2 Closed-Building Conditions
Short-term measurements lasting between two and 90 days should be made
under closed-building conditions. Closed-building conditions are necessary for
short-term measurements in order to stabilize the radon and radon decay product
concentrations and increase the reproducibilrty of the measurement. Windows on a||
levels and external doors should be kept closed (except during normal entry and exit)
during the measurement period. Normal entry and exit include a brief opening and
closing of a door, but--to the extent possible-external doors should not be left open
for more than a few minutes. In addition, external-internal air exchange systems (other
than a furnace) such as high-volume, whole-house and window fans should not be
operating. However, attic fans intended to control attic and not whole building
temperature or humidity should continue to operate. Combustion or make-up air
supplies must not be closed.
In addition to maintaining closed-building conditions during the measurement,
closed-building conditions for 12 hours prior to the initiation of the measurement are a
required condition for measurements lasting less than four days, and are
recommended prior to measurements lasting up to a week in duration. Normal
operation of permanently installed energy recovery ventilators (also known as heat
recovery ventilators or air-to-air heat exchangers) may also continue during
closed-building conditions. In houses where permanent radon mitigation systems
have been installed, these systems should be functioning during the measurement
period.
Closed-building conditions will generally exist as normal living conditions in
northern areas of the country when the average daily temperature is low enough so
that windows are kept closed. Depending on the geographical area, this can be the
period from late fall to early spring. In some houses, the most stable radon levels
occur during late fall and early spring, when windows are kept closed but the house
heating system (which causes some ventilation and circulation) is not used. Available
information about variations of indoor radon levels in a particular area can be used to
choose a measurement time when the radon concentrations are most stable.
It may be necessary, however, to make measurements during mild weather, when
closed-building conditions are not the normal living conditions. It will then be
necessary to establish some more rigorous means to ensure that closed-building
conditions exist prior to and during the measurements.
Those performing measurements in southern areas that do not experience
extended periods of cold weather should evaluate seasonal variations in living
conditions and identify if there are times of the year when closed-building conditions
normally exist. Ideally, measurements should be conducted during those times. The
closed-building conditions must be verified and maintained more riqorouslv when thev
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are not the normal living conditions. Air conditioning systems that recycle interior air
can be operated during the closed-building conditions when radon measurements are
being made. However, homeowners should be aware that any air circulation system
can after the radon decay product concentration without significantly changing the
radon concentration.
Short-term tests lasting just two or three days should not be conducted during
unusually severe storms or periods of unusually high winds. Severe weather will affect
the measurement results in several ways. First, a high wind will increase the variability
of radon concentration because of wind-induced differences in air pressure between
the building interior and exterior. Second, rapid changes in barometric pressure
increase the chance of a large difference in the interior and exterior air pressures,
consequently changing the rate of radon influx. Weather predictions available on local
news stations can provide sufficient information to determine if these conditions are
likely. While unusual variations between radon measurements may be due to weather
or other effects, the measurement system should be checked for possible problems.
During any short-term test, closed-house conditions should be maintained as
much as possible while the test is in progress. In tests lasting less than four days (96
hours), closed-house conditions should be maintained for at least 12 hours before
starting the test. In tests lasting between four and seven days, closed-house
conditions should be maintained while the test is in progress; while recommended,
the 12 hour closed-house condition before the start of the is not required. In tests
lasting more than seven days and less than 90 days, closed-house conditions should
be maintained as much as possible while the test is in progress.
2.3.3 Interpretation of Initial Measurement Results
If the initial measurement result is less than 4 pCi/L, or 0.02 WL, follow-up
measurements are probably not needed. There is a relatively low probability that
mitigation is warranted if the result is less than 4 pCi/L or 0.02 WL (EPA 400-R-92-011;
U.S. EPA 1992g). Even if the measurement result is less than 4 pCi/L, or 0.02 WL,
however, a homeowner may want to test again sometime in the future. If the
occupants' living patterns change or renovations are made to the home and they
begin using a lower level (such as a basement) as a living area, a new test
should be conducted on that level.
The average year-round residential indoor radon level is estimated to be about 1.3
pCi/L, and about 0.4 pCi/L of radon is normally found in outside air. The U.S.
Congress has set a long-term goal that indoor radon levels be no more than outdoor
levels. There is some risk of lung cancer from radon levels below 4 pCi/L, and EPA
recommends that the homeowner consider reducing the radon level if the average of
the first and second short-term measurements or if a long-term follow-up
measurement is between 2 and 4 pCi/L (0.01 and 0.02 WL). While it is not yet
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technologically achievable for all homes to have their radon levels reduced to outdoor
levels, the radon levels in some homes today can be reduced to 2 pCi/L or below.
If the result of the short-term measurement is equal to or greater than 4 pCi/L, or
0.02 WL, the occupant should conduct a follow-up measurement using a short-term or
long-term test, as described in Section 2.4.
2.4 FOLLOW-UP MEASUREMENTS
2.4.1 Rationale
The purpose of a follow-up measurement is to provide the homeowner with
enough information to make an informed decision on whether to mitigate to reduce
radon levels. The follow-up measurement, whether it is short-term or long-term,
provides an additional piece of information to confirm that radon levels are high
enough to warrant mitigation. There are two major reasons why a second
measurement is necessary. First and most important, radon levels fluctuate over time
(see Section 1), and a second short-term measurement, when averaged with the first
test result, will provide a more representative value for the average radon level during
the period of the test, if a long-term follow-up measurement is conducted, that result
should provide an even more representative value for the long-term average radon
concentration. The second reason for making a follow-up measurement prior to
mitigation is that there is a small chance of laboratory or technician error in all
measurements, including radon measurements, and a second test will serve as a
check on the first.
Homes tested using the protocol in this section should not be mitigated on the
basis of a single short-term test. A follow-up test is necessary for mitigation decision-
making regardless of the initial test result.
2.4.2 Short-Term and Long-Term Follow-Up Testing
Follow-up testing should be conducted in the same location as the first
measurement (see Section 2.2).
A follow-up test can be conducted with either a short-term or long-term
measurement device. Long-term tests (> 90 days) will produce a reading that is more
likely to represent the home's year-round average radon level than a short-term test.
However, if the initial test result is high (for example, greater than about 10 pCi/L, or
0.05 WL) or if results are needed quickly, EPA recommends a second short-term test.
This will allow the homeowners to obtain information necessary to decide quickly on
the need for mitigation. If the result of the initial measurement is between 4 pCi/L and
10 pCi/L (or between 0.02 WL and 0.05 WL), then either a short-term or long-term test
can be taken.
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If the long-term follow-up test result is 4 pCi/L, or 0.02 WL, or higher, then EPA
recommends remedial action. Likewise, if the average of the initial and second
short-term results is equal to or greater than 4 pCi/L, or 0.02 WL, radon mitigation is
recommended. These recommendations are summarized in Exhibit 2-1.
As with the initial short-term test, the second short-term test should be conducted
under closed-building conditions (Section 2.3.2). These conditions, however, are not
necessary for long-term tests (those lasting longer than 90 days).
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Section 3: DISCUSSION OF GUIDELINES PRESENTED IN THE
HOME BUYER'S AND SELLER'S GUIDE TO RADON
3.1 INTRODUCTION
The unique nature of a real estate transaction, involving multiple parties and
financial interests, presents radon measurement issues not encountered in non-real
estate testing. EPA's objectives for issuing recommended protocols for radon
measurements made for real estate transactions are intended to reduce
misunderstanding and protect public health in several ways. First, EPA seeks to
provide home buyers, sellers, real estate agents, and testing organizations with a
common basis of understanding of the recommended procedures for radon
measurements. Second, the widespread implementation of this guidance will produce
results that are reliable indicators of the need for mitigation. A significant proportion of
radon measurements are conducted as part of real estate transactions, and all
aspects of these transactions are carefuHy scrutinized, so specific guidance from EPA
can help to ensure good quality measurements. When the results are interpreted
properly and the appropriate remedial action is taken, these protocols will assist the
buyer and seller in reducing the risk to the occupants from radon exposure. The
availability of a nationally-recognized protocol for measurement and for the
interpretation of the measurement results will greatly assist home buyers, sellers, real
estate agents, builders, lenders, and radon measurement experts.
These protocols are designed for use in residences, as described in the EPA
document, Home Buyer's and Seller's Guide to Radon (EPA 402-R-93-003; U.S. EPA
1993). While that document offers general information on radon and testing, this
report presents a more technical description of EPA recommendations, including
discussion of guidelines for the interpretation of measurement results. As with all of
EPA's policies regarding radon measurements, these guidelines have been developed
after review and assistance from the radon measurement community and EPA's
Science Advisory Board. Technical information on a variety of radon measurement
methods is available in the EPA report titled Indoor Radon and Radon Decay Product
Measurement Device Protocols (EPA 520-402-R-92-004; EPA 1992c; these and other
EPA publications are available from the U.S. Government Printing Office [see Exhibit 1-
1], or your State or Regional EPA radon office, see Appendix A).
The radon testing guidelines in the Home Buyer's and Seller's Guide to Radon
have been developed specifically to deal with the time-sensitive nature of home
purchases and sales. These guidelines are somewhat different from the guidelines in
other EPA publications, such as the 1992 Citizen's Guide to Radon (EPA 402-K-92-
001; U.S. EPA 1992a), which provide radon testing and reduction information for non-
real estate situations.
There are also guidelines in the Home Buyer's and Seller's Guide to Radon to
deal with the potential for radon test interference. There are approaches that can be
used to increase confidence in measurement results by detecting measurement
interference. For example, a device that offers a variety of ways to detect tampering
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may serve to deter, as well as detect, interference with the device's operation or with
proper closed-building measurement conditions. Potential tampering indicators
Include the ability of a device to record changes in radon levels, temperature, and
humidity, or to detect movement of or around the device during the measurement.
Refer to Section 3.5 for information and recommendations for interference-resistant
testing.
EPA investigated a variety of options for real estate testing. EPA recommends
testing in advance of putting the house on the-market. A long-term test, which is
conducted for longer than 90 days, gives the most representative indication of the
annual average radon concentrations in a home. However,.for time-sensitive real
estate transactions, the Home Buyer's Guide offers three short-term testing options.
Short-term tests are conducted from two days to 90 days, depending on the
measurement device. Based on extensive quantitative analyses to evaluate the
frequency with which long-term and short-term testing results lead to the same
mitigation decision, EPA and its independent Science Advisory Board concluded that
short-term tests can be used to assess whether a home should be remediated.
The reliability of each radon measurement made for a real estate transaction, or
for any purpose, is highly dependent upon the existence and documentation of an
adequate quality assurance program implemented by both the tester and the analysis
laboratory. All the parties involved in the real estate transaction depend upon the
testers doing their job. This includes ensuring that the measurements are valid via the
performance of quality control measurements and activities, and detecting
measurement interference. The protocols outlined in this section were developed by
EPA for testers and homeowners adhering to the quality assurance practices
summarized in Section 4.4 of this report, and in EPA's Indoor Radon and Radon
Decay Product Measurement Device Protocols (EPA 520-402-R-92-004- U S EPA
1992c).
Three options were determined to be satisfactory and are described here. The
availability of three options will allow flexibility on the part of the party purchasing the
test. Each of these options will produce results that can be used to determine the
need for mitigation.
Both Options 1 and 2 require the use of two measurements made for similar
durations. Both measurements should report results in units of pCi/L or both in WL
Similar durations means that the two measurements must be made for a similar time
period, with a two-hour grace period. Specific information on measurement methods
(listed in Exhibit 3-1) can be found in EPA's Indoor Radon and Radon Decay Product
Measurement Device Protocols (EPA 520-402-R-92-004; U.S. EPA 1992c).
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Exhibit 3-1
Radon and Radon Decay Product Measurement
Method Categories
A (DCi/Ll
AC Activated charcoal adsorption
integrating
AT Alpha track detection
LS Charcoal liquid scintillation
CR Continuous radon monitoring
PB Pump-collapsible bag
SC Evacuated scintillation cell
(three-day integrating)
EL Electret ion chamber: long-term
ES Electret ion chamber: short-term
UT Unfiltered track detection
B
-------
3.2 OPTIONS FOR REAL ESTATE TESTING
3.2.1 Option 1; Sequential Testing
Sequential tests should be conducted under conditions that are as similar as
possible, in the same location, and using similar devices and durations. Both should
produce results in the same units (pCi/L or WL). That is, both methods should be
from column A or both from column B of Exhibit 3-1. Any EPA-recognized method
may be used. In addition, the results of the first test should not be reported prior to
making the second measurement: both measurements should be reported at the
same time in order to discourage tampering that may occur if the first test is known to
be greater than 4 pCi/L or 0.02 WL Note that measuring with different methods (e.g.,
with AC and ES) may increase the potential for differences (e.g., measurement bias)
between the results. The results of both measurements should be reported, and the
average of the two results should be used to determine the need for mitigation. There
will be some variation between the two results, which may be caused by the radon
levels fluctuating in response to weather or other factors. If the variation is unusually
large, it may be due to weather or other effects, but the measurement system should
be checked for possible problems.
3.2.2 Option 2: Simultaneous Testing
This option involves the use of two tests, conducted simultaneously and side-by-
side, made for similar durations, and producing results in the same units (i.e., both
methods should be from column A or both should be from column B of Exhibit 3-1).
Any EPA-recognized method may be used. As with Option 1, using different methods
for the two measurements (for example, ES and LS) may increase the potential for
differences between the two results. The two test results should be averaged to
determine the need for remedial action. The collocated devices should be placed four
inches (10 centimeters) apart.
Because radon measurements, like any measurements, usually do not produce
exactly the same results, even for simultaneous testing, there will usually be a
difference between the two results. EPA offers the following guidance to testers for
judging when two simultaneous, side-by-side measurements disagree to such an
extent that two additional measurements should be performed.
The results of the simultaneous measurements will fall into one of the three
categories discussed below and illustrated in Exhibit 3-2.
3.2.2.1 Both Measurement Results Equal To or Greater Than
4 pCI/L for 0.02 WL)
In this case, the average of the two results will be equal to or greater than 4
pCi/L, or 0.02 WL, and mitigation is recommended. The tester should report both
measurement results as well as the average of the two results.
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Exhibit 3-2
Deciding on a Retest When Measurements Vary Significantly
3
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"11NP 18*
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3.2.2.2 Both Measurement Results Less Than A pCl/L for 0.02 WL1
In this case, the average of the two measurements will be less than 4 pCi/L, or
0.02 WL, and both measurement results and the average result should be reported to
the client.
3.2.2.3 One Measurement Result Greater Than 4 oCl/L tor 0.02 WU. and
One Measurement Result Leas Than 4 pCl/L tor 0.02 WU
This is a special situation in which the average of the results is critical. To assist
testers in ensuring that the difference between two measurements is small enough so
that clients may have confidence in, and understand, the results, EPA offers the
following simple guidance.
If the higher result is twice or more the lower result, then the two results are not
within a factor of two, and a retest should be conducted. Section 3.2.2.5 provides
language for informing the client that a retest is warranted.
If the higher result is less than twice the lower result, then the two results are
within a factor of two, and a retest is not necessary. The results of both
measurements and the average of the two results should be reported to the client.
(See Section 4 for more detailed information on quality assurance and quality control
procedures.)
3.2.2.4 Precision Recommendations
Measurements near the lower limit of detection (LLD) for the measurement
system often have large and varying precision errors, and it is difficult to assign any
sort of probability level to very low results.
Simultaneous measurement results that are-equal to-4-pCi/L, or 0.02 WL, or
greater should, however, exhibit some agreement. An example control chart for the
precision that may be expected is shown as Exhibit B-2 in Appendix B, which was
constructed using an average relative percent difference of 14 percent. (Relative
percent difference is defined as the difference divided by the average.) Using Exhibit
B-2, a relative percent difference greater than 36 percent should be observed less
than one percent of the time. Based upon this, EPA recommends that any side-by-
side, simultaneous measurements with results greater than or equal to 4 pCi/L, or 0.02
WL, and which exhibit a relative percent difference greater than 36 percent, be cause
for informing the client that the two results do not show good agreement. However,
since both results are greater than 4 pCi/L, or 0.02 WL, EPA recommends mitigation in
this case. Testers should investigate the source of the error (see Appendix B).
Results between 2 pCi/L (or 0.01 WL) and 4 pCi/L (or 0.02 WL), should also
exhibit some agreement. The level of agreement expected should be based upon the
tester's experience with duplicate measurements made with that technique in this
-range of radon concentrations. An example control chart for the precision that may
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be expected in this region is shown as Exhibit B-3 in Appendix B, which was
constructed using an average relative percent difference of 25 percent. Using this
chart, a relative percent difference between duplicates greater than 67 percent should
be observed less than one percent of the time. Based upon this, EPA recommends
that any side-by-side, simultaneous measurements with results less than 4 pCi/L or
0.02 WL, and which exhibit a relative percent difference greater than 67 percent 'be
cause for informing the client that the two results do not show good agreement' but
that both are less than 4 pCi/L, or 0.02 WL, and therefore mitigation is not
recommended. Testers should investigate the source of the error (see Appendix B).
3.2.2.5 Recommended Language for Informing the Client that a Retest is
Warranted
If a retest is warranted (see Section 3.2.2.3), EPA recommends that the tester
inform the client that EPA provides guidance for how well two measurements should
agree, that the measurements performed fall outside the range, and that a retest
should be conducted. A retest should consist of measurements performed according
to one of the protocols outlined in Sections 3.2.1, 3.2.2, or 3.2.3.
3.2.3 Option 3: Single Test Option
This option requires an active continuous monitor (method CR or CW) that has
the capability to integrate and record a new result at least hourly. Shorter integration
periods and more frequent data logging afford greater ability to detect unusual
variations in radon or radon decay product concentrations. The minimum
measurement period is 48 hours. The first four hours of data from a continuous
monitor may be discarded or incorporated into the result using system correction
factors (EPA 520-402-R-92-004; EPA 1992c). There must be at least 44 contiguous
hours of usable data to produce a valid average. (The "backing out" of data [i e
removal of portions imbedded in the two days] to account for weather or other "
phenomena will invalidate the measurement.) The periodic results should be
averaged to produce a result that is reported to the client.
If the monitor cannot integrate over a period of one hour or less, then an
additional (secondary) passive or active measurement device must be used The
second measurement, which may be made with a passive or active device can be
used simultaneously or sequentially, as discussed in Options 1 and 2 (Sections 321
and 3.2.2). If the two measurements are performed simultaneously, their results
should be evaluated following the guidance in Section 3.2.2. If the two measurements
were performed sequentially, it can be expected that the two results will be different
As discussed in Section 3.2.1, the difference between sequential tests may be due to
radon levels fluctuating in response to weather or other factors.
In general, confidence in a radon measurement can be increased by performing
another measurement with a second measurement device. However, there are other
approaches or features that can be used to increase the confidence of a
measurement result obtained using active monitor devices. These approaches include
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the use of device self-diagnostic features, and data validation or verification
procedures, that could be employed before and/or after the measurement. Examples
of such approaches are the use of check sources before and after each
measurement, and the use of spectrum readouts. These capabilities are examples,
and different technologies may be able to perform other similar self-diagnostic or
quality assurance checks. Other features that increase the confidence of a single
active test include (but are not limited to) the ability to check air flow rates and voltage
meters before and after each measurement. Measurement companies should
incorporate such checks into their routine instrument performance checks as part of
their standard operating procedures.
Additional features that can increase confidence in measurement results are
those that detect measurement interference; these features are discussed in Section
3.5. For example, a device that offers a variety of ways to detect tampering may serve
to deter, as well as detect, interference with the device's operation or with proper
closed-building measurement conditions. Potential tampering indicators include the
ability of a device to record changes in temperature, humidity, or movement of or
around the device during the measurement.
Instruments with greater efficiency or sensitivity, or a high signal-to-noise ratio
(see Glossary for definitions of these terms), can achieve results with a smaller
uncertainty than instruments with low efficiency, poor sensitivity, or low signal-to-noise
ratio. Greater efficiencies, sensitivities, or a high signal-to-noise ratio may also facilitate
tampering detection by being more sensitive to fluctuations in radon levels. There
have been recommendations for setting minimum efficiency standards for active
devices at 16 counts per hour per pCi/L EPA plans to conduct research to establish
minimum standards in the future for all categories of devices, passive as well as active
detectors. The reliability of any type of equipment, however, needs to be established
and documented via a complete quality assurance program. This includes routine
instrument performance checks prior to and after each measurement, annual
calibrations, semi-annual instrument cross-checks, the performance of duplicate
measurements in 10 percent of the measurement locations, and frequent background
and spiked measurements.
3.3 MEASUREMENT LOCATION
EPA recommends that measurements made for a real estate transaction be
performed in the lowest level of the home which is currently suitable for
occupancy. This means the lowest level that is currently lived-in, or a lower level that
is not currently used (such as a basement, which a buyer could use for living space
without renovations). Measurements should be made in a room that is used regularly,
such as a living room, playroom, den, or bedroom. This includes a basement that can
be used as a recreation room, bedroom, or playroom. This provides the buyer with
the option of using a lower level of the home as part of the living area, with the
knowledge that it has been tested for radon.
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3.4 MEASUREMENT CHECKLIST
EPA presents the following checklist to help ensure that a radon measurement
conducted for a real estate transaction is done properly. The seller, or an EPA-listed
or State-listed tester, should be able to confirm that all the items in this checklist have
been followed. If the tester cannot confirm this, another test should be made.
Before the radon test:
Notify occupants of the importance of proper testing conditions. Give
occupants written instructions or a copy of the EPA Home Buyer's and
Seller's Guide to Radon (EPA 402-R-93-003; U.S. EPA 1993), or a State-
required alternative, and explain the directions carefully.
The radon measurement service and device used should be listed by EPA's
National Radon Measurement Proficiency (RMP) Program (EPA 520/1-91-006-
U.S. EPA 1991) or listed by your State. Follow the manufacturer's
instructions that come with the device.
If a testing professional conducts the test, only EPA-listed or State-listed
individuals should be hired. Their photo identification should be provided to
the client or homeowner at the time of, or before, the test, and the
contractor's identification number should be clearly visible on the test report.
The test should include method(s) to prevent or detect interference with
testing conditions or with the testing device itself.
Conduct the radon test for a minimum of 48 hours. Some devices must be
exposed for longer than the 48-hour minimum.
In homes with an active radon reduction system, check that the fan is
running at least 24 hours before starting a short-term test lasting less than
four days. Air exhaust equipment, like radon reduction system fans and
small exhaust fans that typically operate for short periods (e.g., bathroom
fan) may be used during the test.
EPA recommends that short-term radon testing, which lasts for no more than
a week in length, be done under closed-building conditions. Closed-building
conditions means keeping all windows closed, keeping doors closed except
for normal entry and exit, and not operating fans or other machines that bring
in air from outside. Note that fans that are part of a radon reduction system
or small exhaust fans operating for only short periods of time may run durina
the test. a
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When doing short-term testing lasting less than four days, ft is Important to
maintain closed-building conditions for at least 12 hours before the beginning
of the test and for the entire test period. Do not operate fans or other
machines that bring in air from the outside.
During the radon test:
Maintain closed-building conditions during the entire time of a short-term test,
especially for tests shorter than one week in length.
Operate the home's heating and cooling systems normally during the test.
For tests lasting less than one week, only operate air conditioning units that
recirculate interior air.
Do not disturb the test device at any time during the test.
If a radon reduction system is in place, make sure the system is working
properly and will be in operation during the entire radon test.
After a radon test:
If a high radon level is confirmed, fix the home. Pages 21 to 23 of'EPA's
Home Buyer's and Seller's Guide to Radon (EPA 402-R-93-003; U.S. EPA
1993) recommend the next steps that should be taken, such as contacting a
qualified radon reduction contractor to lower the home's radon level.
The radon tester or homeowner should be able to verify or provide
documentation asserting that testing conditions were not violated during the
testing period.
3.5 INTERFERENCE-RESISTANT TESTING
EPA strongly encourages the use of radon testing devices with interference-
resistant features inherent in, or associated with, the device.
Interference with a radon measurement is defined as the altering of test
conditions prior to or during the measurement to either change the radon or decay
product concentrations or alter the performance of the measurement equipment. The
following discussion reviews some of the types of test interferences and methods of
detecting and preventing such interferences.
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Test interference typically causes measurement results to be different than if all
proper test conditions were maintained. False low results have been primarily
associated with testing during a real estate transaction, although they also happen
when the occupants of the dwelling are not properly informed about the necessary
test conditions. Test interference can also inadvertentJy increase measurement results,
although the intent is generally to lower the results.
The current occupant may have an interest in the test results being as low as
possible to avoid hindering the sale of the dwelling or incurring the added expense of
having to install a mitigation system. The potential for test interference puts the
professional radon tester into the position of verifying that the equipment and the
required test conditions have been maintained. A measurement result that is below
the action guideline may be suspect if the tester cannot verify that the necessary test
conditions were maintained.
If the tester arrives at a property and finds windows or doors open, or suspects
that closed-building conditions were not maintained for 12 hours prior to arrival, then
the tester should extend the test period to account for this condition.
3.5.1 influencing Test Area Concentration
The primary method of temporarily reducing radon levels is to ventilate the test
area with outdoor air. Ventilation will slow down radon entry by both reducing
negative pressure in the test area and by diluting the reduced radon concentration.
Even small openings of a single window in the test area can have a large effect.
Ventilating the floors above the test area has significantly less effect, unless the test
area is connected with the ventilated room (s) by an operating central air handling
system.
Radon decay product levels are sensitive to air movement. As air movement
increases, decay products will plate out on walls and other surfaces, including fans, :
thereby reducing airborne decay product concentrations. Decay products will be
further reduced if the fan also includes a filter. Radon levels are, however, not affected
by filtering or air movement.
It is also possible to alter concentrations in a tight room if the heating system is
operating in an abnormal fashion. Since this may not be the typical operation of the
system, it is, in effect, interfering with normal house conditions.
It is important to recognize that test interference can increase radon or decay
product levels, despite intent to lower the results.
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3.5.2 Equipment Interference
The primary method of interfering with testing equipment is to move the detector
to an area of low radon concentration. Other types of interference vary in their ability
to influence different types of detectors. For example, interfering with the air sampling
mechanisms can maintain the radon concentration at the time of interference, or cause
a large decrease in the reported concentration. Similarly, covering a decay product or
charcoal detector could cause a large drop in the reported values, while other types of
radon detectors would only show a reduced response time to changes in the test area
level. In addition, charcoal detectors are sensitive to heat. Some active radon
monitors and open face charcoal canisters are also sensitive to high humidity. Any
detector that yields a single result could be turned off or sealed in its container or lid
during most of its exposure period.
3.5.3 Preventing Interference
EPA recommends that a radon measurement conducted for a real estate
transaction be performed using tamper-resistant testing techniques. It is more
advantageous for the tester to take steps to prevent interference rather than to simply
detect ft. Preventing interference can best be accomplished by:
Educating the parties to a real estate transaction about the necessary test
conditions.
Including in the standard documentation for each measurement an
agreement signed by the parties involved in the real estate transaction listing
the necessary test conditions and their agreement not to interfere with the
conditions.
The agreement should also state .that the tester, in their discretion may nullify
the test results if ft appears that, in their professional judgement, the test
results were rendered unreliable.
Informing the parties that interference with the test conditions may increase
the radon levels.
Informing the parties that the tester is using interference-detecting
techniques.and that these allow the detection and documentation of test
interference.
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3.5.4 Interference-Resistant Detectors
The following is a partial list of common equipment and measures that can serve
to prevent and/or detect test interference. There may be other methods available.
Equipment that offers a combination of tamper-detecting features also offers a greater
chance of detecting interference.
The ability to integrate and record frequent radon measurements over short
intervals (an hour or less) is an important tamper detection feature.
Continuous (active) monitors that provide frequent measurements can
indicate unusual concentration changes that can be indicators of test
interference.
Measuring other parameters may provide additional indicators of test
interference, such as a detector tilt indicator or a continuous recording of
pump flow rate.
A motion indicator can also indicate when the detector was approached or
moved.
ซ A simultaneous, several-day continuous measurement of both radon and
decay product concentrations will produce a series of equilibrium ratio
values. These values can be inspected for unusual swings or abnormal
levels, possibly indicating interference.
Measurement of CO2 levels can indicate changes in the test area infiltration
rate of outdoor air.
ซ The performance of a grab radon measurement, a grab decay product
measurement, or both, before and after a longer-term measurement can offer
useful information. For example, the initial and final concentrations and
equilibrium ratios can be compared for consistency. Note: The results of
measurements lasting less than 48 hours (e.g., grab samples) should not be
used as the basis for deciding to fix a home.
ซ Frequent temperature readings may help to indicate changes in the test area
infiltration rate of outdoor air.
ป Humidity (as well as temperature) recordings can be especially helpful in
identifying potential unusual changes in test conditions that occur during the
test period.
Instruments that do not allow occupants to view preliminary results (via a
visible printer or screen) may reduce occupants' interference.
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Placement indicators can also indicate if a detector has been tampered with
or moved. The position of the detector should be noted so that, upon
retrieval, any handling of the detector can be indicated by a change in its
position. A detector may be hung or placed slightly over the edge of its
support to discourage covering it. Passive detectors may be hung or
suspended in a radon-permeable bag that uses a strap and seal to prevent
removing or covering it. Cages can be equipped with a movement indicator
to deter handling of the cage or the detector within it.
Seals can aid in detecting and discouraging test interference, and they are
especially important in the absence of other tamper detection measures.
Non-sealable caulks and/or tapes can be used to verify that detectors have
not been altered or moved, or that windows or non-primary exterior doors
have not been opened. Seals alone will not prevent excessive ventilation
through primary doors.
Seals should be placed on the lowest operable windows and non-primary
exterior doors, as well as between the detector and its support and any other
components of the detector that could be tampered with. It may be
advisable to place a seal on the furnace control fan switch. It may also be
necessary to attach to the caulk seal something fragile that protrudes out, to
indicate any handling or covering of the detector.
A number of different products or combination of products can be used for
tamper seals. For a seal to be effective, it needs at least the following unique
qualities.
The seal must adhere readily to a multitude of surfaces, and yet be easily
removed without marring the surface.
It needs to be non-resealable or show evidence of disturbances
It must be unique enough to prevent easy duplication.
It should be visible enough to discourage tampering.
The tamper resistance of the seal can be increased by using a caulk over the
seal edges or by slicing a large portion of the center of the seal to ensure the
seal is broken in case of tampering.
Most paper or plastic tapes and caulks have only some of these qualities.
There are, however, a number of seals manufactured specifically for radon
testing. It would be advisable to use one of these products and follow the
manufacturer's installation recommendations. The best caulking to use as a
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seal is a removable weatherstripping caulk. This type of caulking adheres
readily to most surfaces, yet comes off easily without leaving a mark or being
resealable.
Upon retrieval of the detector, the tester should carefully inspect the following:
That all closed-building conditions are still being maintained;
ii Any changes in the detector placement;
n The condition of all seals; and
Any abnormal variations in any of the measurements made.
This information should be recorded, as described in Section 4.3.5.
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4.1
Section 4: GENERAL PROCEDURAL RECOMMENDATIONS
INTRODUCTION
This section outlines basic procedural recommendations for anyone involved in
the measurement of radon in homes for both real estate and non-real estate related
measurements.
4.2 INITIAL CLIENT INTERVIEW
Reasonable efforts should be made to determine whether the home is new
and/or occupied, and who will be in charge of the home during the measurement
period. Testing organizations should inform the client and other parties to the real
estate transaction of:
The appropriate EPA testing recommendations as outlined in this report,
the 1992 Citizen's Guide to Radon (EPA 402-K-92-001; U.S. EPA 1992a),
or the Home Buyer's and Seller's Guide to Radon (EPA 402-R-93-003;
U.S. EPA 1993); and
The types of devices they will be using for that test, and EPA
documentation indicating that the testing organization or individual is
RMP-listed for that device.
4.3 MEASUREMENT RECOMMENDATIONS
4.3.1 Selecting a Measurement Approach
The purpose of the measurements, as well as budget and time constraints,
dictate the protocol used. Measurements made for the purpose of assessing the
need for mitigation of one's own property should be made according to the guidance
discussed in Section 2 of this document; Section 3 outlines options for protocols for
measurements made for real estate transactions. Organizations that provide
consultant services, or place or retrieve devices, should review the protocol options
and the clients' needs, and inform clients of the buildings and test period conditions
necessary for conducting valid measurements. In some areas, companies may offer
different types of radon service agreements. Some agreements allow for a one-time
fee that covers both testing, and if needed, radon reduction.
The organizations or individuals performing the measurement service should
use only those specific devices or methods for which that organization or individual is
listed according to the National RMP Program (EPA 520/1-91-006; U.S. EPA 1991).
Adherence to the EPA device protocols, Indoor Radon and Radon Decay Product
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Measurement Device Protocols (EPA 520-402-R-92-004; U.S. EPA 1992c) is a
requirement for participation in the RMP Program.
4.3.2 Written Measurement Guidance
Measurement organizations should provide clients with written measurement
instructions that clearly explain the responsibilities of the client and the other parties to
the real estate transaction during the test period. Written and verbal guidance should
be in accordance with EPA's Indoor Radon and Radon Decay Product Measurement
Device Protocols (EPA 520-402-R-92-004; U.S. EPA 1992c) and guidance published in
the RMP Program Handbook (EPA 520/1-91-006; U.S. EPA 1991). At a minimum, the
guidance should include the following elements:
A statement of whether the device measures radon or radon decay
products and a discussion of the units in which all results will be
reported.
The results of radon decay product measurements should be reported in
working levels (WL). If the WL value is converted to a radon
concentration and is reported to the homeowner, it should be stated that
this approximate conversion is based on a 50 percent equilibrium ratio
(unless the actual equilibrium ratio is determined). In addition, the report
should indicate that this ratio is an assumed average found in the home
environment; any indoor environment may have a different and varying
relationship between radon and its decay products.
A description of closed-building conditions and a stated requirement that
these conditions be maintained 12 hours prior to and during all
short-term measurements lasting less than four days and preferably for
those lasting up to one week.
Directions that the building's heating, ventilating, and air conditioning
(HVAC) system and any existing mitigation system should be normally
operated 24 hours prior to and during all measurements.
A permanent radon reduction system should be fully operational for at
least 24 hours prior to testing to determine the mitigation system's
effectiveness. The mitigation system is to be operated normally and
continuously during the entire measurement period.
ป Specific information on the minimum and maximum duration of exposure
for the measurement device(s).
If the client will be performing the test, procedures for placing, retrieving,
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and handling the device.
A written non-interference agreement (see Sections 3.5.3 and 4.3.4) to
be signed and returned by the parties to the real estate transaction
which confirms that they followed all instructions and did not interfere
with the conditions or the measurement device.
4.3.3 Conditions for a Valid Measurement
Measurements should not be conducted if temporary radon reduction
measures have been implemented. These include the introduction of unconditioned
air into the home or closure of normally accessible areas of the home. In this case,
the measurement organization or individual should inform the client and other parties
to the real estate transaction that these conditions will invalidate measurement results
and decline to conduct a measurement until the conditions have been corrected.
A permanent radon reduction system should be fully operational for at least 24
hours prior to testing to determine the mitigation system's effectiveness. The
mitigation system is to be operated normally and continuously during the entire
measurement period.
4.3.4 Non-interference Controls
The measurement organization should provide parties to a real estate
transaction with a written statement that discusses the importance of proper
measurement conditions and of not interfering with the measurement device or
building conditions. The reader should refer to Section 3.5.3 for more information on
non-interference agreements.
Organizations that place and retrieve devices should, in addition to providing
written guidance, take steps to identify attempts to interfere with the measurement
device or building conditions. There is increasing use of non-interference agreements
signed by parties involved in real estate transactions to help prevent interference with
the radon test and test conditions. The reader should refer to Section 3.5 for more
information on tamper-resistant testing.
The signed non-interference agreement, a description of all non-interference
controls employed, and a statement addressing any observed breaches of the
non-interference agreement/controls should be made part of the permanent
measurement documentation for each measurement.
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4.3.5 Measurement Documentation
Measurement organizations should record sufficient information on each
measurement in a permanent log to allow for future data comparisons, interpretations,
and reporting to clients. EPA recommends that a measurement log be kept with the
following information and be maintained for five years. Additional method-specific
documentation is outlined in EPA's Indoor Radon and Radon Decay Product
Measurement Device Protocols (EPA 520-402-R-92-004; U.S. EPA 1992c).
A copy of the final report, including the measurement results, and the
statement outlining any recommendations concerning retesting or
mitigation provided to the building occupant or agent.
The address of the building measured, including zip code.
The exact locations of all measurement devices deployed. It is advisable
to diagram the test area, noting the exact location of the detector.
Exact start and stop dates and time of the measurement period as
required for analysis.
A description of the device used, including its RMP device identification
number and serial number if any.
A description of the condition of any permanent vents, such as crawl
spacf vents or combustion air supply to combustive appliances.
ป The name and RMP identification number (EPA 520/1-91-014-3N; U.S.
EPA 1992e) of the serivce or analysis organizations used to analyze
devices.
The name and RMP identification number (or State license number) of
the individual who conducted the test.
ป A description of any variations from or uncertainties about standard
measurement procedures, closed-building conditions, or other factors
that may affect the measurement result.
A description of any non-interference controls used and copies of signed
non-interference agreements.
A record of any quality control measures associated with the test, such
as results of simultaneous or secondary measurements.
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4.4 QUALITY ASSURANCE IN RADON TESTING
Anyone providing measurement services using radon or radon decay product
measurement devices should establish and maintain a quality assurance program.
These programs should include written procedures for attaining quality assurance
objectives and a system for recording and monitoring the results of the quality
assurance measurements described below. EPA offers general guidance on
preparing quality assurance plans (QAMS-005/80; U.S. EPA 1980); a draft standard
prepared by a radon industry group is also available (AARST 1991). The quality
assurance program should include the maintenance of control charts and related
statistical data, as described by Goldin (Goldin 1984), by EPA (EPA 600/9-76-005; U.S.
EPA 1984), and in Appendix B of this document.
4.4.1 Calibration Measurements
Calibration measurements are measurements made in a known radon
environment, such as a calibration chamber. Detectors requiring analysis, such as
charcoal canisters, alpha track detectors, electret ion chambers, and radon progeny
integrating samplers are exposed in a calibration chamber and then analyzed.
Instruments providing immediate results, such as continuous working level and radon
monitors, should be operated in a chamber to establish individual instrument
calibration factors.
Calibration measurements must be conducted to determine and verify the
conversion factors used to derive the concentration results. These factors are
determined normally for a range of concentrations and exposure times, and for a
range of other exposure and/or analysis conditions pertinent to the particular device.
Determination of these calibration factors is a necessary part of the laboratory
analysis, and is the responsibility of the analysis laboratory. These calibration
measurement procedures, including the. frequency, of tests .and the number of devices
to be tested, should be specified in the quality assurance program maintained by
manufacturers and analysis laboratories.
4.4.2 Known Exposure Measurements
Known exposure measurements or spiked samples consist of detectors that
have been exposed to known concentrations in a radon calibration chamber. These
detectors are labeled and submitted to the laboratory in the same manner as ordinary
samples to preclude special processing. The results of these measurements are used
to monitor the accuracy of the entire measurement system. Suppliers and analysis
laboratories should provide for the blind introduction of spiked samples into their
measurement processes and the monitoring of the results in their quality assurance
programs. All organizations providing measurement services with passive
devices should conduct spiked measurements at a rate of three per 100
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measurements, with a minimum of three per year and a maximum required of six per
month. Providers of measurements with active devices are required to recalibrate
their instruments at ieast once every 12 months and perform cross-checks with RMP-
listed devices at least once every six months. Participation in EPA's National RMP
Program will not satisfy the need for annual calibration, as this Program is a
performance test, not a calibration procedure.
4.4.3 Background Measurements
Background measurements are required both for continuous monitors and for
passive detectors requiring laboratory analysis. Users of continuous monitors must
perform sufficient instrument background measurements to establish a reliable
instrument background and to check on instrument operation. For more specific
information on how often background measurements should be made, refer to EPA's
Indoor Radon and Radon Decay Product Measurement Device Protocols (EPA 520-
402-R-004; U.S. EPA 1992c).
Passive detectors requiring laboratory analysis require one type of background
measurement made in the laboratory and another in the field. Suppliers and analysis
laboratories should measure routinely the background of a statistically significant
number of unexposed detectors from each batch or lot to establish the laboratory
background for the batch and the entire measurement system. This laboratory blank
value is subtracted routinely (by the laboratory) from the field sample results reported
to the user, and should be made available to the users for quality assurance
purposes. In addition to these background measurements, the organization
performing the measurements should calculate the lower limit of detection (LLD) for its
measurement system (Altshuler and Pasternack 1963, ANS11989, U.S. DOE 1990).
This LLD is based on the detector and analysis system's background and can restrict
the ability of some measurement systems to measure low concentrations.
Providers of passive detectors should employ field controls (called blanks)
equal to approximately five percent of the detectors that are deployed, or 25 each
month, whichever is smaller. These controls should be set aside from each detector
shipment, kept sealed and in a low radon environment, labeled in the same manner as
the field samples to preclude special processing, and returned to the analysis
laboratory along with each shipment. These field blanks measure the background
exposure that may accumulate during shipment and storage, and the results should
be monitored and recorded. The recommended action to be taken if the
concentrations measured by one or more of the field blanks is significantly greater
than the LLD is dependent upon the type of detector. More information is available in
EPA's Indoor Radon and Radon Decay Product Measurement Device Protocols (EPA
520-402-R-92-004; U.S. EPA 1992c).
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4.4.4 Duplicate Measurements
Duplicate measurements provide a check on the quality of the measurement
result, and allow the user to make an estimate of the relative precision. Large
precision errors may be caused by detector manufacture, and/or improper data
transcription or handling by suppliers, laboratories, or technicians performing
placements. Precision error can be an important component of the overall error, so it
is important that all users monitor precision.
Duplicate measurements for both active and passive detectors should be side-
by-side measurements made in at least 10 percent of the total number of
measurement locations, or 50 each month, whichever is smaller. The locations
selected for duplication should be distributed systematically throughout the entire
population of samples. Groups providing measurement services to homeowners can
do this by providing two measurements, instead of one, to a random selection of
purchasers, with the measurements made side-by-side. As with spiked samples
introduced into the system as blind measurements, the precision of duplicate
measurements should be monitored and recorded in the quality assurance records.
The analysis of data from duplicates should follow the methodology described in
Appendix B of this document. If the precision estimated by the user is not within the
precision expected of the measurement method, the problem should be reported to
the analysis laboratory and the cause investigated.
4.4.5 Routine Instrument Performance Checks
Proper functioning of analysis equipment and operator usage require that the
equipment and measurement system be subject to routine checks. Regular
monitoring of equipment and operators is vital to ensure consistently accurate results.
Performance checks of analysis equipment includes the frequent use of an instrument
check source. In addition, important components of the device (such as a pump and
pump flow rate, battery, or electronics) should be checked prior to each measurement
and the results noted in a log. Each user should develop methods for regularly (daily,
or at least prior to each measurement) monitoring their measurement system, and for
recording and reviewing results.
4.4.6 Quality Assurance Plans
All organizations should develop, implement, revise periodically, and maintain a
detailed quality assurance plan (GAP) appropriate to each device or method used.
This is a requirement for participation in EPA's National Radon Measurement
Proficiency (RMP) Program. Specific guidance on the necessary quality control
measures for each measurement method is provided in EPA's Indoor Radon and
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Radon Decay Product Measurement Device Protocols (EPA 520-402-R-92-004; U.S.
EPA 1992C).
Organizations that do not use continuous monitors or do not analyze detectors
also need to write and follow a QAP, and conduct quality control measurements.
These include duplicate, blank, and spiked measurements as described in Section
4.4. For further information on EPA's RMP Program, please contact:
RMP Program Information Service
Research Triangle Institute
3040 Cornwallis Road-Building 7
P.O. Box 12194
Research Triangle Park, NC 27709-2194
(919-541-7131/FAX -7386)
4.5 STANDARD OPERATING PROCEDURES
Organizations performing radon measurements should have a written,
device-specific standard operating procedure (SOP) in place for each radon
measurement system they use. An SOP must include specific information describing
how to operate and/or analyze a particular measurement device. Organizations that
analyze devices should develop their own SOP or adapt manufacturer-developed
SOPs for their devices. Organizations that receive results from a laboratory should
have a device-specific SOP for each brand/model/type of device that they use. All
SOPs should be consistent with the appropriate protocol outlined in EPA's Indoor
Radon and Radon Decay Product Measurement Device Protocols (EPA 520-402-R-92-
004; U.S. EPA 1992c).
4.6 PROVIDING INFORMATION TO CONSUMERS
Organizations should provide the customer with the following information:
Devices that will be placed by the customer must be accompanied by
instructions on how to use the device. These instructions should be
consistent with EPA's Indoor Radon and Radon Decay Product
Measurement Device Protocols (EPA 520-402-R-92-004; U.S. EPA 1992c)
and include specific information on the minimum and maximum length of
time that the device must be exposed.
The service organization should inform clients about sources of
information on mitigation, such as EPA's Consumer's Guide to Radon
Reduction (EPA 402-K-92-003; U.S. EPA 1992b), and other information
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available through their State Radon office. The organizations should also
provide any State-required brochures which provide information on
mitigation.
If service organizations distribute the Consumer's Guide brochure, it
should be reproduced in its entirety.
4.7 REPORTING TEST RESULTS
Organizations should return radon measurement results to clients within a few
weeks of retrieving exposed devices or receiving an exposed device which has been
delivered for analysis. At a minimum, the client report should contain the following
information:
Measurement results reported in the units that the device measures. Any
measurement results based on radon gas (pCi/L of air) should be
reported to no more than one decimal place, e.g., 4.3 pCi/L Any
measurement result based on radon decay products (WL) should be
reported to no more than three decimal places, e.g., 0.033 WL. Any
conversions from WL to pCi/L or from pCi/L to WL should be presented
and explained clearly.
If the WL value is converted to a radon concentration, it should be stated
in the report to the homeowner that this approximate conversion is
based on a 50 percent equilibrium ratio (unless the actual equilibrium
ratio is determined). In addition, the report should indicate that this ratio
is typical of the home environment, but that any indoor environment may
have a different and varying relationship between radon and its decay
products.
The dates of the measurement period and address of the building
tested.
A description of the device used, its manufacturer, model or type, and
the device identification (serial) numbers.
The name and RMP identification numbers of the organization and
individual placing and retrieving the device and the organization
analyzing the device, if they are different.
A statement concerning any observed tampering or deviations from the
required test conditions.
Organizations that offer measurement services with grab sampling
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devices should provide clients with written notification stating that grab
sample results can be useful diagnostic tools, but should not be used for
deciding whether or not to mitigate.
4.8 TEMPORARY RISK REDUCTION MEASURES
Contractors should refer the occupants of the house and real estate agents to
EPA's Interim Radon Mitigation Standards (U.S. EPA 1992d) or the Consumer's Guide
to Radon Reduction (EPA 402-K-92-003; U.S. EPA 1992b) for information on
temporary and permanent risk reduction measures.
If any radon reduction efforts are identified during measurement procedures,
testers should inform clients and other parties to the real estate transaction that
altered conditions during the measurement will invalidate the results and decline to
conduct a measurement until the conditions have been corrected.
4.9 RECOMMENDATIONS FOR MITIGATION
The measurement organization should inform consumers that EPA
recommends fixing houses with radon levels equal to or greater than 4 pCi/L, and that
EPA recommends in its "Consumer's Guide to Radon Reduction" the use of EPA
Radon Contractor Proficiency (RCP)-listed and/or State-listed mitigation contractors to
perform the work (EPA 402-K-92-003; U.S. EPA 1992b).
Organizations should refer customers to their State radon office for copies of
EPA's "Consumer's Guide to Radon Reduction" (EPA 402-K-92-003; U.S. EPA 1992b)
and a list of EPA RCP-proficient and State-listed mitigators.
Homes should also be tested again after they are fixed to be sure that radon
levels have been reduced. If the occupants' living patterns changes and they begin
occupying a lower level of their home (such as a basement), the home should be
retested on that level. In addition, it is a good idea for homes to be retested
sometime in the future to be sure radon levels remain low.
4.10 WORKER SAFETY
Individuals and organizations should comply with all applicable Occupational
Safety and Health Administration (OSHA) standards and guidelines relating to
occupational worker exposure, health, and safety. Information on worker health and
safety contained in EPA or State publications is not considered a substitute for any
provisions of the Occupational Safety and Health Act of 1970 or for any standards
issued by OSHA.
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APPENDIX A
STATE AND EPA REGIONAL RADON OFFICES
A.1 STATE RADIATION AND RADON OFFICES
The State radiation and radon offices distribute EPA's radon-related technical
and guidance documents. , '
Alabama
Division of Radiation Control
State Department of Public Health
434 Monroe Street Room 510
Montgomery, AL 36130-1701
(205) 242-5315
(800) 582-1866 in Alabama
Alaska
State Department of Health and Social
Services
Division of Public Health
P.O. Box H
Juneau, AK 99811-0610
(907) 465-3019
(800) 478-4845 in Alaska
Arizona
State Radiation Regulatory Agency
4814 South 40th Street
Phoenix, AZ 85040
(602) 255-4845
Arkansas
Division of Radiation Control and
Emergency Management
State Department of Health
4815 West Markham Street
Little Rock, AR 72205-3867
(501) 661-2301
California
State Department of Health Services
Environmental Management Branch
601 North 7th Street
P.O. Box 942732
Sacramento, CA 94234-7320
(916)324-2208
(800) 745-7236 in California
Colorado
Radiation Control Division
State Department of Health
4210 East 11th Avenue
Denver, CO 80220
(303) 692-3057
(800) 846-3986 in Colorado
Connecticut
State Department of Health Services
Radon Program
150 Washington Street
Hartford, CT 06106-4474
(203) 566-3122
Delaware
Office of Radiation Control
State Bureau of Environmental Health
Division of Public Health
P.O. Box 637
Dover, DE 19903
(302) 739-5728
(800) 554-4636 in Delaware
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District of Columbia
D.C. Department of Consumer and
Regulatory Affairs
614 H Street, N.W.
Room 1014
Washington, D.C. 20001
(202) 727-5728; hotline
Florida
Office of Radiation Control
State Department of Health and
Rehabilitative Services
1317 Winewood Boulevard
Tallahassee, FL 32399-0700
(904) 488-1525
(800) 543-8279 in Florida;
consumer inquiries only
Georgia
State Department of Human Resources
878 Peachtree Street
Room 100
Atlanta, GA 30309
(404) 657-6534
(800) 745-0037 in Georgia
Guam
Guam Environmental Protection Agency
IT&E Harmon Plaza
D-107
130 Rojas Street
Harmon, Guam 96911
(617) 646-8863
Hawaii
Radiation Branch
State Department of Health
591 Ala Moana Boulevard
Honolulu, HI 96813-2498
(808) 586-4700
Idaho
State Department of Health and Welfare
Bureau of Preventive Medicine
450 West State Street
Boise, ID 83720
(208) 334-6584
(800) 445-8647 in Idaho
Illinois
State Department of Nuclear Safety
1301 Knotts Street
Springfield, IL 62703
(217) 786-7127
(800) 325-1245 in Illinois
Indiana
Radiological Health Section
State Board of Health
1330 West Michigan Street
P.O. Box 1964
Indianapolis, IN 46206
(317) 633-0150
(800) 272-9723 in Indiana
Iowa
Radon Control Program
Bureau of Radiological Health
State Department of Public Health
Lucas State Office Building
Des Moines, IA 50319-0075
(515) 242-5992
(800) 383-5992 in Iowa
Kansas
Radiation Control Program
Environmental Health Services
State Department of Health and
Environment
109 SW 9th Street
6th Floor, Mills Building
Topeka, KS 66612
(913) 296-1561
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Kentucky
Radiation Control Branch
Division of Community Safety
State Department of Health Services
Cabinet for Human Resources
275 East Main Street
Frankfort, KY 40621
(502) 564-3700
Louisiana
Radiation Protection Division
Louisiana Department of Environmental
Quality
P.O. Box82135
Baton Rouge, LA 70884-2135
(504) 925-7042
(800) 256-2494 in Louisiana
Maine
Department of Human Resources
Division of Health Engineering
State House, Station 10
Augusta, ME 04333
(207) 287-5676
(800) 232-0842 in Maine
Maryland
Radiological Health Program
State Department of the Environment
2500 Broening Highway
Baltimore, MD 21224
(410) 631-3300
(800) 872-3666 in Maryland
Massachusetts
State Department of Public Health
Western MA Health Office
23 Service Center
Northampton, MA 01060
(413)586-7525
(800) 445-1255
Michigan
Division of Radiological Health
Bureau of Environmental and
Occupational Health
State Department of Public Health
3423 North Logan Street/
Martin L King Jr. Blvd.
P.O. Box30195
Lansing, Ml 48909
(517) 335-8190
Minnesota
State Indoor Air Quality Unit
925 Delaware Street, SE
P.O. Box 59040
Minneapolis, MN 55459-0040
(612) 627-5012
(800) 798-9050 in Minnesota
Mississippi
Division of Radiological Health
State Department of Health
3150 Lawson Street
P.O. Box 1700
Jackson, MS 39215-1700
(601) 354-6657
(800) 626-7739 in Mississippi
Missouri
Bureau of Radiological Health
State Department of Health
1730 East Elm
P.O. Box 570
Jefferson City, MO 65102
(314) 751-6083
(800) 669-7236 in Missouri
Montana
Occupational Health Bureau
State Department of Health and
Environmental Sciences
Cogswell Building A113
Helena, MT 59620
(406) 444-3671
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Nebraska
Division of Radiological Health
State Department of Health
301 Centennial Mall, South
P.O. Box 95007
Lincoln, NE 68509
(402)471-2168
(800) 334-9491 in Nebraska
Nevada
Radiological Health Section
State Health Division
505 East King Street, Room 203
Carson City, NV 89710
(702)687-5394
New Hampshire
Bureau of Radiological Health
State Div. of Public Health Services
Health and Welfare Building
Six Hazen Drive
Concord, NH 03301
(603) 271-4674; hotline
(800) 852-3345x4674 in NH
New Jersey
Radiation Protection Programs
Bureau of Environmental Radiation
Department of Environmental Protection
and Energy
CN 415
729 Alexander Road
Trenton, NJ 08625-0415
(609) 987-6396
(800) 648-0394 in New Jersey
New Mexico
Hazardous and Radioactive Materials
Bureau
New Mexico Environment Department
525 Camino De Los Marquez
P.O. Box 26110
Santa Fe, NM 87502
(505) 827-4300
New York
Bureau of Environmental Radiation
Protection
State Health Department
Two University Place
Albany, NY 12203
(518) 458-6451
(800) 458-1158 in New York
North Carolina
Division of Radiation Protection
State Department of Environment,
Health, and Natural Resources
P.O. Box 27687
Raleigh, NC 27611-7687
(919) 571-4141
North Dakota
Division of Environmental
Engineering
State Department of Health
1200 Missouri Avenue, Room 304
P.O. Box 5520
Bismarck, ND 58502-5520
(701) 221-5188
Ohio
Ohio Department of Health
Bureau of Radiological Health Services
246 N. High Street
P.O. Box 118
Columbus, OH 43266-0118
(614) 644-2727
(800) 523-4439 in Ohio; hotline
Oklahoma
Radiation Protection Division
Oklahoma State Department of Health
P.O. Box 53551
Oklahoma City, OK 73152
(405) 271-5221
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Oregon
Department of Human Resources
State Health Division
1400 SW 5th Avenue
Portland, OR 97201
(503) 731-4014
Pennsylvania
State Department of Environmental
Protection
Bureau of Radiation Protection
P.O. Box 2063
Harrisburg, PA 17120
(717) 783-3595
(800) 237-2366 in Pennsylvania
Puerto Rico
Radiological Health Division
G.P.O. Call Box 70184
Rio Pierdras, Puerto Rico 00936
(809) 767-3563
Rhode island
Division of Occupational and
Radiological Health
State Department of Health
206 Cannon Building
3 Capitol- Hill
Providence, Rl 02908
(401) 277-2438
South Carolina
Bureau of Radiological Health
State Department of Health and
Environmental Control
2600 Bull Street
Columbia, SC 29201
(803) 734-4631
(800) 768-0362 in South Carolina
South Dakota
State Department of Water and
Natural Resources
523 E. Capitol
Pierre, SD 57501
(605)773-3351
(800) 438-3367
Tennessee
State Department of Health and
Environment
Division of Air Pollution Control
701 Broadway, 4th Floor
Nashville, TN 37247-3101
828-28861(615)532-0733
(800) 232-1139 in Tennessee
Texas
Radiological Assessment Program
Bureau of Radiation Control
State Department of Health
1100 West 49th Street
Austin, TX 78756
(512) 834-6688
Utah
Division of Radiation Control
Department of Environmental Quality
160 North 1950 West
Salt Lake, UT 84114-4850
(801) 538-6734
Vermont
Occupational and Radiological
Health Operations
Division of Occupational and
Radiological Health
State Department of Health
10 Baldwin Street,
Administrative Bldg.
Montpelier, VT 05602
(802)865-7730
(800)640-0601 in Vermont
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Virginia
Bureau of Radiological Health
State Department of Health
109 Governor Street
Richmond, VA 23219
(804) 786-5932
(800) 468-0138 in Virginia
Virgin Islands
Contact the U.S. EPA, Region 2 in
New York
Mail Code 2AWM-RAD
26 Federal Plaza
New York, NY 10278
(212)264-4110
Washington
Division of Radiation Protection
State Department of Health
Airdustrial Building 5, LE-13
Olympia, WA 98504
(206) 753-4518
(800) 323-9727 in Washington; hotline
West Virginia
Office of Environmental Health
Services
Industrial Hygiene Division
State Bureau of Public Health
151 11th Avenue
South Charleston, WV 25303
(304) 558-3526
(800) 922-1255 in West Virginia
Wisconsin
Radon Program
Radiation Protection Section
Division of Health
State Department of Health and
Social Services
P.O. Box 309
Madison, Wl 53701-0309
(608) 267-4795
Wyoming
Environmental Health Programs
State Department of Health
Hathway Building, 4th Floor
(Room 482)
Cheyenne, WY 82002-0710
(307) 777-6015
(800) 458-5847 in Wyoming
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A.2 EPA REGIONAL RADIATION (RADON) PROGRAM MANAGERS
There are 10 EPA Regional Program Managers, one for each EPA geographical
Region. (Exhibit A-1 of this appendix contains a map showing the States and their
EPA Regions.)
Region 1
Radiation Program Manager, Region 1
U.S. Environmental Protection Agency
John F. Kennedy Federal Building
Room 2311
Boston, MA 02203
(617) 565-4502
Region 2
Chief, Radiation Branch (AWM-RAD)
U.S. Environmental Protection Agency
26 Federal Plaza, Room 1005A
New York, NY 10278
(212)264-4110
Region 3
Radiation Program Manager, Region 3
Special Program Section (3AM12)
U.S. Environmental Protection Agency
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-8326
Region 4
Radiation Program Manager, Region 4
U.S. Environmental Protection Agency
345 Courtland Street, N.E.
Atlanta, GA 30365
(404) 347-3907
Region 5
Radiation Program Manager, Region 5
(5AR26)
U.S. Environmental Protection Agency
230 S. Dearborn Street
Chicago, IL 60604
(312) 353-2206
Region 6
Radiation Program Manager, Region 6
U.S. Environmental Protection Agency
Chief, Technical Section (6T-ET)
Air, Pesticides and Toxics Division
1445 Ross Avenue
Dallas, TX 75202-2733
(214) 655-7223
Region 7
Radiation Program Manager, Region 7
U.S. Environmental Protection Agency
726 Minnesota Avenue
Kansas City, KS 66101
(913) 551-7020
Region 8
Radiation Program Manager, Region 8
(8AT-RP)
U.S. Environmental Protection Agency
999 18th Street, Suite 500
Denver, CO 80202
(303) 293-1709
Region 9
Radiation Program Manager, Region 9
(A-1-1)
U.S. Environmental Protection Agency
75 Hawthorne Street
San Francisco, CA 94105
(415) 744-1048
Region 10
Radiation Program Manager, Region 10
(AT-082) U.S. EPA
1200 Sixth Avenue
Seattle, WA 98101
(206) 442-7660
A-7
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Exhibit A-1
MAP OF EPA REGIONS
Each of the 50 United States, as well as the District of Columbia, the Virgin
islands, and Puerto Rico, has been assigned to one of 10 Federal.Regions. This map
shows the Regional assignments for the 50 States. Puerto Rico and the Virgin Islands
are assigned to Region 2; the District of Columbia is in Region 3.
RI
HI
o
A-8
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APPENDIX B
INTERPRETATION OF THE RESULTS OF SIDE-BY-SIDE MEASUREMENTS
B.1 ASSESSMENT OF PRECISION
Radon and working level measurements, like all measurements, usually do not
produce exactly the same results, even for collocated measurements. It is therefore
critical to understand, document, and monitor the variability, or precision, of the
measurements. This knowledge and proper documentation will allow you to
characterize precision error to clients. Furthermore, the continual monitoring of
precision provides a check on every aspect of the measurement system.
The objective of performing simultaneous or duplicate measurements is to
assess the precision error of the measurement method, or how well two side-by-side
measurements agree. This precision error is the "random" component of error (as
opposed to the calibration error, which is systematic). The precision error, or the
degree of disagreement between duplicates, can be composed of many factors.
These include the error caused by the random nature of counting radioactive decay,
slight differences between detector construction (for example, small differences in the
amount of carbon in activated carbon detectors), and differences in handling of
detectors (for example, differences in accuracy of the weighing process, and
variations of analysis among detectors).
There is a variety of ways to quantitatively assess the precision error based on
duplicate measurements. It is first necessary to understand that precision is
characterized by a distribution: that is, your side-by-side measurements will exhibit a
range of differences. There is some chance that any level of disagreement will be
encountered, due merely to the statistical fluctuations of counting radioactive decays.
The probability of encountering a very large difference between duplicates is smaller
than the chance of observing a small difference similar to those that are routinely
observed. It is important to recognize that a few high precision errors do not
necessarily mean that the measurement system is flawed.
Ideally, the results of duplicates should be assessed in a way that allows for the
determination of what level of chance is associated with a particular difference
between duplicates. This will allow for the pre-determination of limits for the allowable
differences between duplicates before an investigation into the cause of the large
differences is made. For example, the warning level, or the level of discrepancy
between duplicates which triggers an investigation, may be set at a five percent
probability. This level is a difference between duplicates that is so large that, when
compared with previous precision errors, should only be observed five percent of the
time. A control limit, where further measurements should cease until the problem is
corrected, may be set at one percent probability.
B-1
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A control chart for duplicates is not as simple as a control chart used to
monitor instrument performance, as for a check source. This is because the
instrument's response to a check source should be fairly constant with time.
Duplicates are performed at various radon concentrations, however, and the total
difference between two measurements is expected to increase as radon levels
increase.
Use of statistics such as the relative percent difference (RPD; difference divided
by tine mean) or the coefficient of variation (COV; standard deviation divided by the
mean) can be used in a control chart for duplicate measurements at radon
concentrations where the expected precision error is fairly constant in proportion to
the mean, e.g., at levels greater than around 4 pCi/L or 0.02 WL At lower
concentrations, for example, between 2 pCi/L (or 0.01 WL) and 4 pCi/L (or 0.02 WL), a
control chart may be developed by plotting these same statistics; however, the
proportion of the precision error to the mean will be greater than that proportion at
levels above 4 pCi/L or 0.02 WL At concentrations less than about 2 pCi/L, or 0.01
WL, the lower limit of detection may be approached, and the precision error may be
so large as to render a control chart not useful.
Example control charts, using three different statistics, are described in the
following sections.
B.2 EXAMPLE CONTROL CHARTS FOR PRECISION
Before a control chart can be developed, it is necessary to know, from a history
of making good quality measurements with the exact measurement system (detectors,
analysis equipment, and procedures), the level of precision that is routinely
encountered when the system is operating well or "in control." ft is that "in control"
precision error that forms the basis of the control chart, and upon which all the
subsequent duplicate measurements will be judged. There are two ways of initially
determining this "in control" level. The first, and preferable, way is to perform at least
20 duplicate pairs of measurements at each range of radon concentrations for which a
control chart is to be prepared. For example, if you will only assess precision at
concentrations greater than 4 pCi/L, or 0.02 WL, you will need at least 20 pairs of
measurements at concentrations greater than 4 pCi/L, or 0.02 WL, to assess the "in
control" level. The average precision error (RPD or COV) should be the "in control"
level.
The second way to initially set the "in control" precision error level is to use a
level that has been used by others, and that is recognized by industry and EPA as a
goal for precision, for example, a 10 percent COV (corresponding to a 14 percent
RPD). After at least 20 pairs of measurements are plotted, it will become apparent
B-2
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whether the 10 percent COV (or 14 percent RPD) is appropriate for your system If it
is not, a new control chart (using the guidelines below) should be prepared so that
the warning and control limits are set at the correct probability limits for your system.
B.2.1 Sequential Control Chart Based on Coefficient of Variation
It can be shown (Iglewicz and Myers 1970, EPA 600/9-76-005; U.S. EPA 1984)
that when the expected precision is a constant function of the mean, control limits can
be expressed in terms of the COV (COV=S/Xm; where S is the variance or the square
of the standard deviation, and ^ is the mean or average of the two measurements)
One method for obtaining percentiles for the distribution of the COV is to apply a chi-
squared fo2) test:
(Equation 1)
where B = n[1 + (1/COV2)];
COVn = the observed COV of the n* pair (the pair that is to be evaluated); and
COV = the "in control" COV (e.g., 10 percent at levels greater than 4 pCi/L).
For duplicates, where n=2, Equation 1 becomes
X2- [2 + (2/COV2)J[COVn2/(2 + COV,,2)] (Equation 2)
For a value of 0.10 for COV, jt further reduces to
= 202[COVn2/(2 + COVn2)]
(Equation 3)
Referring to a % chart, you learn that the probability of exceeding a x2 of 3 84 is only
five percent. Inserting this value of 3.84 for %2 and solving for COVn, produces a
COVn of 0.20. This level of probability forms the warning level shown in Exhibit B-1
The control limit corresponds to a x2 of 6.63 and a COVn of 0.26, where the
probability of exceeding those values is only one percent.
This sequential control chart should be used by plotting results from each pair
on the y-axis, and noting the date and measurement numbers on the x-axis.
B-3
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B.2.2 Sequential Control Chart Baaed on Relative Percent Difference
The RPD (or percent difference) is another expression of precision error, and is
given by
RPD =
(Equation 4)
For
(Equation 5)
The control limits for RPD can be obtained simply by multiplying the control limits for
COV by the square root of two, or 1.41. These limits are shown in Exhibit B-2. This
sequential control chart for RPD should be used in the same way as the control chart
for COV, that is, with the vertical scale in units of RPD and the horizontal scale in units
of date and measurement numbers.
A control chart using the statistic RPD based on an "in control" level of 25
percent RPD is shown in Exhibit B-3. The warning level and control limit are set at 50
percent and 67 percent, respectively. Use of these limits may be appropriate for
measured radon concentrations less than 4 pCi/L
B-4
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Exhibit B-1
ซ
Control Chart* for Coefficient of Variation (COV)
Based on an "In Control" Level of 10%
(For duplicates where average .>4 pCi/L or 0.02 WL)
26%
Control Limit
I
'o
ฃ
j>
_o
s
5
20%
- Expect to see duplicates produce COV greater
than 26% only 1% of the time (1/100 chance)
Warning Level
10%
- Expect to see duplicates produce COV greater
than 20% only 5% of the time (1/20 chance)
'In Control" Level
- Expect to see results routinely produce this COV
-II-
Date and Measurement Number
COV=standard deviation of two measurements divided by their average
Example: Detector A=5 pCi/L, B=6 pCi/L, COV=13%
If COV exceeds the control limit-cease measurements until the problem is identified
and corrected.
If COV exceeds the warning level-follow guidance in Section B.3 and see Exhibit B-5.
*As calculated from guidance provided in "Quality Assurance Handbook for Air
Pollution Measurement Systems: Volume I" (EPA 600/9-76-005; U.S. EPA 1984)
B-5
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Exhibit B-2
Control Chart* for Relative Percent Difference (RPD)
Based on an "In Control" Level of 14% (=COV of 10%)
(For duplicates where average ^4 pCi/L or 0,02 WL)
36%
i
1
28
14%
Control Limit
- Expect to see duplicates produce RPD greater
than 36% only 1% of the time (1/100 chance)
Warning Level
- Expect to see duplicates produce RPD greater
than 28% only 5% of the time (1/20 chance)
'In Control" Level
- Expect to see results routinely produce this
Date and Measurement Number
RPD=d'rfference between two measurements divided by their average
Example: Detector A=5 pCi/L, B=6 pCi/L, RPD=18%
If RPD exceeds the control limit-cease measurements until the problem is identified
and corrected.
If RPD exceeds the warning level-follow guidance in Section B.3 and see Exhibit B-5.
*As calculated from guidance provided in "Quality Assurance Handbook for Air
Pollution Measurement Systems: Volume I" (EPA 600/9-76-005; U.S. EPA 1984)
B-6
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3
ฃ
0)
Exhibit B-3
Control Chart* for Relative Percent Difference (RPD)
Based on an "In Control" Level of 25% (=COV of 18%)
(For duplicates where average <4 pCi/L or 0.02 WL)
67%
50%
Control Limit
1^I^^^M
- Expect to see duplicates produce RPD greater
than 67% only 1% of the time (1/100 chance)
Warning Level
- Expect to see duplicates produce RPD greater
than 50% only 5% of the time (1/20 chance)
25%J
In Control" Level
- Expect to see results routinely produce this RPD
Date and Measurement Number
RPD=difference between two measurements divided by their average
Example: Detector A=2 pCi/L, B=3 pCi/L, RPD=40%
If RPD exceeds the control limit-cease measurements until the problem is identified
and corrected.
If RPD exceeds the warning level-follow guidance in Section B.3 and see Exhibit B-5.
*As calculated from guidance provided in "Quality Assurance Handbook for Air
Pollution Measurement Systems: Volume I" (EPA 600/9-76-005; U.S. EPA 1984)
B-7
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B.2.3. Range Control Chart
A range control chart (Goldin 1984) can be constructed to evaluate precision,
using the statistics of the range (difference between two measurements) plotted
against the average of the two measurements. The control limits are again based on
the variability of the measurements, as decided upon from previous results or using an
industry standard (e.g., 10 percent).
In this type of control chart, the limits are expressed in terms of the mean range
, where, for n=2,
(Equation 6)
where s(x) is the standard deviation of a single measurement, which reflects counting
and other precision errors. Goldin shows that the limits can be expressed as follows:
Control limit = 3.69 s(x)
(Equation 7)
Warning level = 2.53 s(x)
(Equation 8)
An example range control chart, using an assumed s(x) equal to 10 percent of the
mean concentration, is shown in Exhibit B-4. The chart is used by plotting the range
versus average concentration as duplicate measurements are analyzed.
B-8
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Exhibit B-4
Range Control Chart to Evaluate Precision
(Limits Based on sfxJ^O.
0 5 10 15 20 25
Average Value of Two Measurements, pCi/L
measurements until the problem is identified
If results exceed the warning level-follow guidance in Section B.3 and see Exhibit B-5.
B-9
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B.3 INTERPRETATION OF PRECISION CONTROL CHARTS
The control chart should be examined carefully every time a new duplicate
result is plotted. If a duplicate result falls outside the control limit, repeat the analyses
if possible. If the repeated analyses also fall outside the control limit, stop making
measurements and identify and correct the problem.
If any measurements fall outside the warning level, use the table in Exhibit B-5.
Refer to the row showing the number of duplicate results outside the warning level. If
the total number of duplicate results accumulated in the control chart is contained in
column A, investigate the cause of the high level of precision error but continue
making measurements. If the total number of duplicate results on the chart is
contained in column B, stop making measurements until the cause for the high
precision error is found, and it is determined that subsequent measurements will not
suffer the same high level of precision error.
Note that the example control charts shown here are simplifications of actual
conditions, because they are premised on the assumption that the precision error is a
constant fraction of the mean concentration. In fact, the total precision error may best
be represented by a different function of the mean concentration, for example, the
square root of the concentration. The most accurate control chart can be rendered
by a range control chart using the measurement uncertainty expressed as the
standard deviation, s(x), expected at the concentrations where measurements are
made. If the precision error is not a constant fraction of the mean, the control limits
will not appear as straight lines, but may exhibit changing slope. However, methods
discussed here present a conservative way to monitor, record, and evaluate precision
error and are very useful for comparing observed precision errors with an industry
standard.
B-10
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Exhibit B-5
Criteria for Taking Action for Measurements Outside the Warning Level*
Number of
Duplicate Results
Outside the
Warning Level
Total Number of Duplicates
Investigate, But
Continue Operations
Stop Operations
Until Problem is
Corrected
B
8-19
2-7
17-34
8-16
29-51
17-28
41-67
29-40
54-84
41-53
67-100
54-66
Modified from Goldin (Goldin 1984) and based upon cumulative probability
tables of the binomial distribution.
B-11
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GLOSSARY
Accuracy: The degree of agreement of a measurement (X) with an accepted
reference or true value (T); usually expressed as the difference (or bias)
between the two values (X - T), or the difference as a percentage of the
reference or true value (100[X - TjA), and sometimes expressed as a ratio
(X/T).
Active radon/radon decay product measurement device: A radon or radon decay
product measurement system which uses a sampling xlevice, detector, and
analysis system integrated as a complete unit or as separate, but portable
components. Active devices include continuous radon monitors, continuous
working level monitors, and grab radon and grab working level measurement
systems, but do not include devices such as electret ion chamber devices
activated carbon or other adsorbent systems, or alpha track devices!
Alpha particle: Two neutrons and two protons bound as a single particle that is
emitted from the nucleus of certain radioactive isotopes in the process of
radioactive decay.
Background instrument (analysis system, or laboratory) count rate: The nuclear
counting rate obtained on a given instrument with a background counting
sample. Typical instrument background measurements are:-
Unexposed carbon: for activated carbon measurement systems.
Scintillation vial containing scintillant and sample known to contain no
radioactivity: for scintillation counters.
Background measurements made with continuous.radon monitors
exposed onjy to radon-free air (aged air or nitrogen).
Background field measurement (blanks): Measurements made by analyzing
unexposed (closed) detectors that accompanied exposed detectors to the field
Tlie purpose of field background measurements is to assess any exposure to
the detector caused by radon exposure other than from the concentration in
the environment to be measured. Results of background field measurements
are subtracted from the actual field measurements before calculating the
reported concentration. Background levels may be due to electronic noise of
the analysis system, leakage of radon into the detector, detector response to
gamma radiation, or other causes.
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Background radiation: Radiation arising from radioactive materials, the sun, and
parts of the universe, other than that under consideration. Background
radiation due to cosmic rays and natural radioactivity is always present;
background radiation may also be due to the presence of radioactive
substances in building materials.
Becquerel (Bq): The International System of Units (SI) definition of activity. 1 Bq = 1
disintegration per second.
Calibrate: To determine the response or reading of an instrument relative to a series
of known values over the range of the instrument; results are used to develop
correction or calibration factors.
Check source: A radioactive source, not necessarily calibrated, which is used to
confirm the continuing consistent and satisfactory operation of an instrument.
Client: The individual or parties who hire(s) the radon tester.
Closed House Conditions: During any short-term test, closed-house-conditions
should be maintained as much as possible while the test is in progress. In tests of
less than 4 days duration, closed-house-contiions should be maintained for at least
12-hours before starting the test and for the duration of the test. While closed-house-
conditions are not required before the start of tests that are between 4 and 90-days
long, closed-house-conditions should be maintanined as much as possible.
Coefficient of variation (COV), relative standard deviation (RSD): A measure of
precision, calculated as the standard deviation (s or a) of a set of values
divided by the average (Xave or n), and usually multiplied by 100 to be
expressed as a percentage.
COV = RSD = (s/Xave) x 100 for a sample,
or
COV' = RDS' = (a//u) x 100 for a population.
See Relative percent difference.
Curie (Ci): A commonly used measurement unit for radioactivity in the United States,
specifically the approximate rate of decay for a gram of radium = 37 billion
decays per second. A unit of radioactivity equal to 3.7 x 1010 disintegrations
per second.
G-2
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Duplicate measurements: Two measurements made concurrently and in the same
location, side-by-side. Use to evaluate the precision of the measurement
method.
Efficiency, intrinsic detector: The relationship between the number of events
recorded (counts, voltage lost, tracks) and the number of radioactive particles
incident upon the sensitive element of the detector per unit time. Efficiencies
for radon detectors are commonly expressed in terms of the calibration factor
which is the number of events (counts) per time (hour or minute) per radon '
concentration (pCi/L). Methods with high efficiencies will exhibit more counts
(signal) per time in response to a given radon level than will a method with a
low efficiency.
Equilibrium ratio, radon: Equilibrium ratio = [WL(100)]/(pCi/L). At complete
equilibrium (i.e., at an equilibrium ratio of 1.0), 1 WL of RDPs would be present
when the radon concentration was 100 pCi/L. The ratio is never 1.0 in a house
Due to ventilation and plate-out, the RDPs never reach equilibrium in a
residential environment. A commonly assumed equilibrium ratio is 0.5 (i e the
decay products are halfway toward equilibrium), in which case 1 WL would
correspond to 200 pCi/L However, equilibrium ratios vary with time and
location, and ratios of 0.3 to 0.7 are commonly observed.
Equilibrium equivalent concentration (EEC): The radon concentration in equilibrium
with its short-lived progeny, that has the same potential alpha energy per
volume as exists in the environment being measured (see working level).
Exposure time: The length of time a specific device must be in contact with radon or
radon decay products to get an accurate radon measurement. Also called
exposure period, exposure parameter, or duration of exposure.
Gamma radiation: Short.wavelength electromagnetic radiation of nuclear origin with
a wide range of energies. a
Integrating device: A device that produces a measurement of the average
concentration over a period of time. Also called a time-integrating device.
Lower limit of detection (LLD): The smallest amount of sample activity which will
yield a net count for which there is confidence at a predetermined level that
activity is present. For a five percent probability of concluding falsely that
activity is present, the LLD may be approximated by a value of 4.65 times the
standard deviation of the background counts (assuming large numbers of
counts where Gaussian statistics can be used [ANS11989, Pasternack and
Harley 1971, U.S. DOE 1990]).
G-3
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Lowest level suitable for occupancy: The lowest level currently lived jn or, a lower
level not currently used, such as a basement, which a prospective buyer could
use for living space without renovations. This includes a basement that could
be used regularly, as for example a recreation room, bedroom, den, or
playroom.
Lowest lived-ln level: The lowest level or floor of a home that is used regularly,
including areas such as family rooms, living rooms, dens, playrooms, and
bedrooms.
Passive radon measurement device: A radon measurement system in which the
sampling device, detector, and measurement system do not function as a
complete, integrated unit. Passive devices include electret ion chamber
devices, activated carbon or other adsorbent systems, or alpha track devices,
but do not include continuous radon/radon decay product monitors, or grab
radon/radon decay product measurement systems.
Plcocurie (pCi): One pCi is one trillionth (10'12) of a curie, 0.037 disintegrations per
second, or 2.22 disintegrations per minute.
Picocurie per liter (pCi/L): A unit of radioactivity corresponding to an average of
one decay every 27 seconds in a volume of one liter, or 0.037 decays per
second in a liter of air or water. 1 pCi/L = 37 Becquerels per cubic meter
(Bq/m3).
Precision: A measure of mutual agreement among individual measurements made
under similar conditions. Can be expressed in terms of the variance, pooled
estimate of variance, range, standard deviation at a particular concentration,
relative percent difference, coefficient of variation or other statistic.
Quality assurance: A complete program designed to produce results which are
valid, scientifically defensible, and of known precision, bias, and accuracy. Includes
planning, documentation, and quality control activities.
Quality control: The system of activities to ensure a quality product, including
measurements made to ensure and monitor data quality. Includes calibrations,
duplicate, blank, and spiked measurements, interlaboratory comparisons, and
audits.
Radon (Rn): A colorless, odorless, naturally occurring, radioactive, inert, gaseous
element formed by radioactive decay of radium (Ra) atoms. The atomic
number is 86. Although other isotopes of radon occur in nature, radon in
indoor air is primarily Rn-222.
G-4
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Radon chamber: An airtight enclosure in which operators can induce and control
different levels of radon gas and radon decay products. Volume is such that
samples can be taken without affecting the levels of either radon or its decay
products within the chamber. y
Relative percent difference (RPD): A measure of precision, calculated by:
RPD - [(IX, - XjJj/X^J x 100
where:
X^concentration observed with the first detector or equipment;
^concentration observed with the second detector, equipment, or absolute
value;
IX, - Xjj^absolute value of the difference between X, and X& and
xซve=average concentration = ((X, +XJ/2).
The RPD and coefficient of variation (COV) provide a measure of precision but
they are not equal. Below are example duplicate radon results and the
corresponding values of RPD and COV:
Rn1
foCi/U
8
13
17
26
7.5
Rn2
foCi/L)
9
15
20
30
10
RPD
COV
12
14
16
14
29
8
10
11
10
20
Note that the RPD/1/2 = COV.
See Coefficient of variation (COV).
Relative standard deviation: See Coefficient of variation.
Sensitivity: The ability of a radon or WL measurement method to produce reliable
measurements at low concentrations. This ability is dependent upon the
variability of the background signal (counts not due to radon or WL exposure)
which the method records, as well as its efficiency. Methods with stable
background rates and high efficiencies will be able to produce reliable
G-5
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measurements at lower concentrations than methods with variable background
rates and low efficiencies. Sensitivity can be expressed in terms'of the lower
limit of detection or minimum detectable activity.
Signal-to-noise ratio: For radon and WL detectors, this term expresses the
proportion of the number of counts due to exposure to radon or WL (signal) to
the number of counts due to background (noise). Measurement methods with
high signal-to-noise ratios will produce more counts due to radon or WL
exposure (signal) in proportion to the background counts (noise) than will
methods with low signal-to-noise ratios. A method with a high signal-to-noise
ratio is more likely to exhibit good sensitivity, i.e., be able to produce reliable
measurements at low concentrations.
Spiked measurements, or known exposure measurements: Quality control
measurements in which the detector or instrument is exposed to a known
concentration in a calibration facility and submitted for analysis. Used to
evaluate accuracy.
Standard deviation (s): A measure of the scatter of several sample values around
their average. For a sample, the standard deviation (s) is the positive square
root of the sample variance:
s =
ฃ (Xi -Xave)
For a finite population, the standard deviation (a) is:
o =
v/N
where p. is the true arithmetic mean of the population and N is the number of
values in the population. The property of the standard deviation that makes it
most practically meaningful is that it is expressed in the same units as the
observed variable X. For example, the upper 99.5 percent probability limit on
differences between two values is 2.77 times the sample standard deviation.
Standard operating procedure: A written document which details an operation,
analysis, or action whose mechanisms are prescribed thoroughly and which is
commonly accepted as the method for performing certain routine or repetitive
tasks.
G-6
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Statisticafjsontrol chart (Shewhart control chart): A graphical chart.with statistical
control limits and plotted values (for some applications in chronological order) of
some measured parameter for a series of samples. Use of the charts provides a
visual display of the pattern of the data, enabling the early detection of time trends
and shifts in level. For maximum usefulness in control, such char> should be
plotted in a timely manner (i.e., as soon as the data are available). See Appendix
B.
Statistical controS chart limits: The limits on control charts that have been derived
by statistical analysis and are used as criteria for action, or for judging whether a
set of data does or does not indicate lack of control. On a means control chart
the warning level (indicating the need for an investigation) may be two standard
deviations above and below the mean, and the control limit (indicating the need
to haft operations until the problem is identified and corrected) may be three
standard deviations above and below the mean.
Systeme Internationale (SI): The International System of Units as defined by the
Conference of Weights and Measures in 1960.
Test Interference: The altering of test conditions prior to or during the measurement in
order to change the radon or radon decay product concentrations or the altering
of the performance of the measurement equipment.
Time integrated measurement: A measurement conducted over a specific time
period (e.g., from two days to a year or more) producing results representative of
the average value for that period.
Uncertainty: The range of values within which the true value is estimated to lie It is
1SS.TmatS of Pฐssible error due to both random errors (imprecision) and
systematic errors (that produce -bias, or inaccuracies),
Working level (WL): Any combination of short-lived radon decay products in one liter
of air thatwill result in the ultimate emission of 1.3 x 10s MeV of potential alpha
energy This number was chosen because it is approximately the alpha energy
released from the decay products in equilibrium with 100 pCi of Rn-222
? W=
Working level months (WLM): (working level x hours of exposure
hours/working month). In SI units, 1 WLM = 6 x 105 Bq-h/m3 (EEC).
G-7
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REFERENCES
Aftshuler, B. and Pasternack, B., 1963, Statistical Measures of the Lower Limit of
Detection of a Radioactivity Counter, Health Phvsics. Vol. 9, pp. 293-298.
American Association of Radon Scientists and Technologists (AARST), 1991 Draft
Standard: Radon/Radon Decay Product Instrumentation Test and Calibration AARST
Park Ridge, New Jersey.
American National Standards Institute (ANSI), 1989, Performance Specifications for
Health Physics Instrumentation-Occupational Airborne Radioactivity Monitoring
Instrumentation, ANSI N42.17B-1989, The Institute of Electrical and Electronics
Engineers, Inc., New York, New York.
Arvela, H.f Voutilainen, A., Makelainen, I., Castren, O., and Winqvist, K. 1988
Companson of Predicted and Measured Variations of Indoor Radon Concentration
Radiat. Prot. Dosim Vol. 24, No. 1/4, pp. 231-235.
Chapin, Jr., F.S., 1974, Human Activity Patterns in the City: Things People Do in Time
and Space, John Wiley and Sons, New York, NY.
5Ud"eyUC>S" Hawthome. A.R.. Wallace, R.G., and Reed, R.P., 1990, Radon-222
Rn-222 Progeny and Rn-222 Progeny Levels in 70 Houses, Health Phvsics Vol. 58,
NO. 3, pp. 297-31 1 .
Fleischer R.L and Turner, L.G., 1984, Indoor Radon Measurements in the New York
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