United States
               Environmental Protection
               Agency
            Office of
            Radiation Programs
            Washington, D.C. 20460
EPA 520/1-86-014-1
February 1987
               Radiation
£EPA
Interim  Protocols For
Screening And Followup
Radon And Radon Decay
Product Measurements

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                                              520/1-86-014
INTERIM PROTOCOLS FOR SCREENING AND FOLLOW-UP RADON
        AND RADON DECAY PRODUCT MEASUREMENTS
        U.S.  Environmental Protection Agency
            Office of Radiation Programs

                    January 1987
                 M. Ronca-Battista
                 P. Magno
                 P. Nyberg

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                              CONTENTS
                                                              Page


Acknowledgements 	   ii

Summary	iii

1.  INTRODUCTION 	    1

2.  SCREENING MEASUREMENTS 	    2
     2.1  Screening Measurement Location 	    3
     2.2  Interpretation of Screening Measurement Results   .    5

3.  FOLLOW-UP MEASUREMENTS 	    7
     3.1  Follow-up Measurement Location 	    7
     3.2  Interpretation of Follow-up Measurement Results   .   10

4.  EXAMPLES OF APPROPRIATE MEASUREMENT LOCATIONS   	   12

5.  RECOMMENDED USES OF GRAB SAMPLING	13

6.  CLOSED-HOUSE CONDITIONS  	   14

7.  INSTRUMENT SELECTION 	   16
     7.1  Continuous Radon Monitors (CRM) or Continuous
          Working Level Monitors (CWLM)  	   16
     7.2  Alpha-Track Detectors  	   17
     7.3  Charcoal Canisters 	   18
     7.4  Radon Progeny Integrating Sampling Units  	   18
     7.5  Grab Sampling	19

References	21

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ACKNOWLEDGEMENTS

     There are many generous  individuals who  have  contributed
substantially to this document during months  of discussion
and review.  The authors wish to  extend  special thanks  to
Thomas Gerusky, Larry Lloyd,  Eileen Hotte,  Larainne  Koehler,
Bill Belanger, Dan Egan, and  the  Environmental Protection
Agency's  (EPA) Radon Action Program staff.  Their  efforts
enabled the  authors to  better address the  needs of homeowners.
States, and  other organizations performing  radon measurements.
                                11

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SUMMARY

     This document presents guidance for making  reproducible
measurements of radon concentrations in residences,  including
recommendations for using the results  to make well-informed
decisions about the need for additional measurements  or
remedial action.  The Environmental Protection Agency (EPA)
recognizes that radon concentrations in homes may  vary greatly
over time (Ge83; He85; St79; F184; Wi86; Ny83).  Furthermore,
concentrations at different locations  in the same  house  often
vary by a factor of two or more (Geo84; Ke84; He85).   Because
of these temporal and spatial variations, the EPA  does not  know
of a way to provide an accurate estimate of health risks  or
make a well-informed decision on the need for remedial action
with a single measurement.  What is necessary, therefore,  is a
logical system for making the fewest measurements  possible,
while ensuring that there are not serious underestimations  of
the concentrations.

     The EPA recommends a two-step measurement strategy  for
assessing radon levels in homes.  The first step is a screening
measurement, made to quickly and inexpensively determine
whether a house has the potential for causing high exposures
to its occupants.  There are two possible outcomes from  a
screening measurement:  (1) if the result is above the
screening level, additional follow-up measurements are
recommended as the second step to both estimate the health  risk
to the occupants and assess the urgency for remedial  action;
and (2) if the result is below the screening level, follow-up
measurements are probably not needed.

     Screening measurements should be made under conditions
that maximize the probability of finding elevated  radon
concentrations.  Screening measurements should be made in the
lowest livable area of the house (closest to the underlying
soil) that the residents now use o_r could adapt for use as  a
living area.  In many houses this will be a basement  that could
be converted to a den, playroom, or bedroom without major
structural changes.  Furthermore, screening measurements
should be made under closed-house conditions when  the doors
and windows of the house are kept closed as much as practical
and the use of ventilation systems mixing indoor and  outdoor
air is minimized.  Both these conditions will help to ensure
that short-term measurements are made during the time of
highest and most stable radon concentration and will  also
increase the reproducibility of the measurements.

     If the screening measurement result is above  4 pCi/1
(0.02 WL), follow-up measurements are recommended.   The EPA
does not recommend taking any significant remedial action on
the basis of a single screening measurement.  Therefore, the
appropriate response to an elevated screening result  is
additional measurements.
                              111

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     Follow-up measurements should be made  in  at  least  two
locations in the house, preferably on each  of  the different
living levels, if there are more  than one.   The  results from
each location should be averaged  to  obtain  an  overall  average
result for the living areas of  the home.

     The duration of the  follow-up measurements  depends on the
magnitude of the screening measurement  result.   If  the
screening result is significantly elevated,  then a  short-term
follow-up measurement should  be made, which  will  minimize  the
additional exposure of the occupants.   If  the  result  is only
moderately elevated, then a full-year schedule of follow-up
measurements is recommended,  with the expectation that  the
additional exposure of the occupants during  that  period will
not significantly increase health risk.  The recommended
follow-up procedure is based  on the  screening  result  as follows:

     1.  If  the screening measurement result is  less  than  about
         4 pCi/1 (or about 0.02 WL), follow-up measurements  are
         probably not needed, as  it  is  highly  unlikely that
         radon levels in  the  living  areas  of the home would
         exceed 4 pCi/1  or  0.02 WL  as an annual  average.

     2.  If  the result of the screening measurement is  greater
         than  about  4 pCi/1  (0.02 WL) but  less than about
         20  pCi/1  (0.1 WL),  EPA recommends  that  the follow-up
         measurements  consist of  12-month  integrated  measure-
         ments made  in several areas of the house.   The average
         annual  concentration in  the living space can be used
         to  estimate  health  risks and  to compare to guidance
          levels  on  the need  for remedial action.  This guidance
          is  available  in "A  Citizen's  Guide to Radon," published
         by  EPA,  the  U.S. Department of Health and Human
         Services,  and  the  Centers for  Disease Control.  This
         pamphlet  can be obtained from  the Government Printing
         Office  by  calling  (202)  275-2091  and  asking  for
         document  number 055-000-00258-4.

      3.   If  the  screening measurement  result is  greater than
          about 20  pCi/1  (0.1 WL), then  EPA recommends that a
          short-term follow-up measurement  over at least 24
          hours be  made  in several living areas of the house
          under closed-house  conditions.  A short-term follow-up
          measurement will minimize  additional significant
          exposure  to the occupants while providing reproducible
          results  that conservatively estimate the annual
          average  concentration.
                                IV

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1.  INTRODUCTION

     This document supplements "Interim Radon and Radon  Decay
Product Measurement Protocols" (EPA 520/1-86-04) prepared  by
the Office of Radiation Programs of the Environmental  Protection
Agency (EPA) and published in February, 1986 (EPA86).  That
report provides guidance for measuring radon concentrations
with continuous radon monitors (CRM), charcoal canisters,
alpha-track detectors (ATD), and grab radon techniques;  it also
provides guidance for measuring radon decay product  concen-
trations with continuous working level monitors (CWLM),  radon
progeny integrating sampling units (RPISU), and grab radon
decay product methods.  The 1986 report includes a discussion
of recommended quality control practices for each method.
Copies of that protocols report, numbered EPA 520/1-86-04, can
be obtained by contacting the Program Management Office
(ANR-458), Office of Radiation Programs, Environmental
Protection Agency, 401 M Street, S.W., Washington, D.C., 20460;
your EPA regional office; or your State radiation control
office.

     This report provides guidelines that are primarily
intended to aid State radiation control programs, other
organizations conducting measurements, and homeowners  who want
detailed information on measurements.  They can be adopted as
part of a State program as particular circumstances  and
resources allow or can be provided by States to homeowners and
measurement firms as recommendations.

     The philosophy presented here serves as the basis
for consistent radon measurements that produce accurate  and
reproducible results within a reasonable time and for  a
reasonable cost.  Consistency is important, because  decisions
about the need for remedial action should be based on  a  common
rationale and comparable measurements.  In addition,
consistency among measurement programs will help assure  valid
comparison of measurement results from different State or
regional programs.  These guidelines will be periodically
evaluated and may be refined to reflect increasing knowledge
and experience with indoor radon.

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2.  SCREENING MEASUREMENTS

     Screening measurements  may  be  conducted  by  homeowners
wanting to make single measurements  to  quickly determine
whether their homes  contain  high radon  concentrations,  and
to decide whether and what type  of  additional measurements
are needed.  Another use  of  screening  measurements is in
multiple-home surveys designed  to efficiently identify  homes
that contain high concentrations.   Screening  measurements
should be inexpensive and simple,  so that  time or  money is  not
wasted in houses that do  not pose a health threat.   However,
the screening measurement alone  usually will  not provide  enough
information to decide on  the need and  timing  of  remedial  action.

     Screening measurements  should  be  made in the  lowest
livable area in the  house that  the  residents  now use or could
adapt for use as a living area,  which  will be the  basement  in
many houses.  (The guidance  presented  here assumes the  source
of radon to be the underlying soil,  rather than  building
materials or water.  If  other radon sources are  suspected,
additional  types of  measurements should be made.)   Any
screening measurement should be made during closed-house
conditions  (described on  page 14) to ensure that information is
obtained on the maximum  concentrations  to  which  the house
occupants may potentially be exposed.   Under  these conditions,
EPA believes that  there  is  a low probability  that  a home with a
low screening result could  have a high long-term average
concentration in  the living  area.

     There  is a growing  body of data indicating  that basement
concentrations  tend  to  be a  factor  of  two  to  three times  higher
(Ge83;  Geo84; F184,  Mo82) and are more reproducible, i.e.,
less variable over  time  (DOE86;  DOE87), than  concentrations
in nonbasement  rooms.   Therefore, if the result  of a screening
measurement  is  very  low,  there is a high probability that the
long-term  average  concentrations in the rooms currently used as
living  areas are  even  lower, and the homeowner  can eliminate
the  need  for further measurements with confidence.

     Screening  measurements  will minimize  the number of false
negatives,  or  homes  that contain concentrations  at which EPA
recommends  that  remedial action be considered but  which would
not  be  identified  as such because of a low measurement  result.
The  outcome of  a  false  positive screening  measurement should be
a follow-up measurement, which would reveal that the concentra-
tions  in  the house  are  low.   However,  the  outcome  of a  false
negative  is no  further  measurements, so that potentially high
concentrations  may  never be identified.  In the  interests of
reducing  radon  exposures, therefore, EPA believes  that  a
significant fraction of  false positives is preferable to a  high
rate  of false  negatives.

     Guidelines for  the duration of screening measurements  are
summarized  in  Table  2-1.

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2.1  Screening Measurement  Location

     The screening measurement  should  be  made  in the room or
area in which the highest and most stable  radon  or radon decay
product concentration  is expected.   The  following criteria
should be used to select this room:

     1.  The measurement should  be made  in a  livable room on a
         level closest to the underlying  soil,  such as  the
         basement.  The room need not  be  currently lived in or
         frequently occupied but should be in  a  condition that
         would allow it to  be easily converted  to a bedroom,
         playroom, den, etc.  Measurements may  be made  in
         unfinished basements, but usually not  in a room that
         would require major structural changes  (such as the
         installation of a  floor) before  it could be used as a
         living area.

     2.  The instrument should be placed  in the  room expected
         to have the lowest ventilation rate,  such  as an
         interior room with tight doors and few  or  no windows.

     3.  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 working level
         measurements.   In  addition,  measurements  should not be
         made in a bathroom, because relatively  little  time  is
         spent in a bathroom and high humidities  may affect  the
         sensitivity of some detectors.   (If radon  in water  is
         expected to be a major contributor to the  concentra-
         tion of airborne radon, diagnostic measurements may be
         made in the bathroom to determine the contribution
         from this source;  however,   such diagnostic  measure-
         ments should not be used to estimate the  resident's
         exposures.)

     These criteria are flexible, and sound judgment is
required as to what space actually constitutes a  room.
Measurements should not be made in closets, cupboards,
sumps,  crawl spaces, or nooks within the foundation.

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                           Table 2-1

                     Screening  Measurements
                  Made in Lowest Livable Area
                 Under Closed-House Conditions
Instrument

Charcoal Canister

Alpha Track Detector
Radon Progeny
Integrated Sampling
Unit

Continuous Working
Level Monitor

Continuous Radon
Monitor

Grab WL*
Sampling Times

2 to 7 days

3 months (or less if laboratory uses
  adequate lower limit of detection)

100 hours minimum, 7 days preferred
6 hours minimum, 24 hours or
  longer preferred

6 hours minimum, 24 hours or
  longer preferred

5 minutes
Grab Rn
5 minutes
 *Grab  measurements,  because  of  the  short  5-minute  sampling
 duration,  have a  relatively large  uncertainty and are
 recommended  only  for  the  purposes  described  on page  13.

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2.2  Interpretation of Screening Measurement Results

     If the screening measurement result  is  less  than  about
4 pCi/1 or 0.02 WL, follow-up measurements are probably  not
needed.  If the screening measurement was made in the  lowest
livable area under the closed-house conditions described on
page 14, there is relatively little chance that the concen-
trations in the general living areas on nonbasement floors  of
the house are greater than about 4 pCi/1  or  0.02  WL as an
annual average.

     If the result of the screening measurement is between
about 4 and 20 pCi/1 or between about 0.02 and 0.1 WL, the
occupant should be aware that, while there is a concern  about
the long-term exposure to these radon concentrations,  there
will probably be no large increase in risk with an additional
12 months of exposure.  Therefore, since guidance for  action
to reduce radon levels is usually expressed  in terms of  annual
average concentrations, we recommend a 12-month measurement
whenever possible.

     If the result of the screening measurement is between
about 20 and 200 pCi/1, or between about 0.1 and  1 WL, a
short-term follow-up measurement should be made within the
next several months under closed-house conditions.  Since the
occupants may be exposed to elevated concentrations in their
living areas, an annual average measurement alone is usually
not recommended because the additional 12 months  of exposure
during the measurement could cause a significant  increase in
health risk.

     If the results are greater than about 200 pCi/1 or  1 WL,
the State radiation control program or regional EPA office
should be contacted for advice on a follow-up measurement
and immediate reductions in concentrations.   The  recommended
follow-up measurements are summarized in Table 2-1.

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                           Table 2-1

       Recommended Actions Based on Results of Screening
                          Measurements
Screening Measurement Result

Greater than 1 WL or  200 pCi/1
Recommended Action

Perform short-term
follow-up measurements
and consider short-term
actions to reduce the
radon levels as soon as
possible
Between  0.1  and  1  WL
       or
Between  20 pCi/1  and  200  pCi/1


Between  0.02 and  0.1  WL
       or
Between  4  pCi/1  and 20 pCi/1
Perform short-term
follow-up
measurements within
several months

Perform follow-up
measurements over
the next 12 months
 Less  than 0.02 WL or 4 pCi/1
Relatively  low
probability of
significant health  risk
from concentrations  in
general  living  areas  of
home; follow-up measure-
ments are probably  not
needed,  but may be  made
at  the  discretion of  the
resident

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3.  FOLLOW-UP MEASUREMENTS

     The results of follow-up measurements will  enable  a
homeowner to make a well-informed decision about  possible
health risks and the need for remedial  action.   As  this
decision often entails spending a significant amount  of money,
follow-up measurements should be reliable and reproducible
estimators of the actual or maximum potential exposures of  the
occupants.

     These guidelines represent EPA's current thinking  on the
optimal method for obtaining these estimates.  An individual
homeowner or a State may be limited by  available  resources  to
making follow-up measurements in only one living  area,  rather
than in two areas as outlined here.  However, in  those
situations involving the investment of  a large amount of  money
or whenever a good estimate of average  concentrations in  living
areas is critical, all efforts should be made to  perform
follow-up measurements in more than one area of  the house.

     If the result of the screening measurement  is between
about 4 and 20 pCi/1 or between about 0.02 to 0.1 WL, measure-
ments to estimate the annual average concentrations should
be made.  The occupant should consider  using a long-term
measurement device, such as a 12-month  alpha-track detector
(ATD), to estimate the annual average concentrations  in the
living areas.  An alternate, but less accurate,  method  for
estimating an annual average is to use  the average of
four measurements made at 3-month intervals.   The year-long
measurement is more reliable for determining long-term
exposure, because both short-term and seasonal variations
will be incorporated into the annual estimate.  All measure-
ments made to estimate annual averages,  whether 12-month
integrated or a series of quarterly measurements, should  be
made under normal living conditions rather than closed  house
conditions.  The results of the four measurements in each
living area are then averaged to estimate the annual average.
Guidelines for the duration of follow-up measurements are
summarized in Table 3-1.

3.1  Follow-up Measurement Location

     The following criteria should be used to select the  rooms
in which follow-up measurements are made.

     1.  The measurements should be made in each level  (floor)
         of the house that is frequently used as a living      ^
         area.  Living areas include family rooms, living
         rooms, dens, playrooms, and bedrooms.

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2.   The measurements should be made in the most frequently
    occupied room in each of the above levels.  A bedroom
    may be a good choice, because most people generally
    spend more time in their bedrooms than in any other
    room in the house (Sz72; Ch74; Mo76).

3.   If there are children in the house,  it may be
    appropriate to measure the concentrations in their
    bedrooms or in other areas where they spend a lot of
    time, such as a playroom.  There is  some concern that
    children may be more sensitive to the effects of
    inhaled radon decay products.

4.   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 working level
    measurements.  In addition, measurements should not be
    made in a bathroom, because relatively little time is
    spent  in a bathroom, and high humidities may affect
    the sensitivity of some detectors.   (If radon in water
    is expected to be a major contributor to the concentra-
    tion of airborne radon, diagnostic measurements may be
    made in the bathroom to determine the contribution
    from this source; however, such diagnostic measure-
    ments  should not be used to estimate the resident's
    exposures.)

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                           Table  3-1

                     Follow-up Measurements
                 Made  in General  Living Areas
Instrument
              If Screening Result is    If Screening  Result  is
Greater than 20 pCi/1
Less than  20 pCi/1
Alpha Track
Detector
3-month measure-
ments (may be less
than 3 months if
laboratory uses
adequate lower limit
of detection), made
under closed-house
(winter) conditions*
12-month measurements
made under normal  living
conditions
Charcoal
Canister
Measurements of
2 to 7 days made
under closed-house
conditions
Four measurements made
under normal living
conditions every 3 months
Radon Progeny 100-hour measure-
Integrating   ments, made under
Sampling Unit closed-house
              conditions
                         Four 100-hour
                         measurements made
                         under normal living
                         conditions every 3 months
Continuous    24-hour measure-
Working Level ments, made under
Monitor       closed-house
              conditions
                         Four 24-hour
                         measurements made
                         under normal living
                         conditions every 3 months
Continuous    24-hour measure-
Radon Monitor ments,  made under
              closed-house conditions
                         Four 24-hour measurements
                         made under normal  living
                         conditions every 3 months
'It the result of the screening measurement is greater than
 about 200 pCi/1, a short-term, follow-up measurement over
 days or weeks may be appropriate.

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3.2  Interpretation of Follow-up Measurement Results

     The purpose of the follow-up measurement  is  to estimate
the long-term average radon or radon decay  product concentra-
tions in general living areas with  sufficient  confidence  to
allow an informed decision to be made  about  risk  and  the  need
for remedial action.  It  should be  noted  that  if  the  results  of
the screening measurement was above  20 pCi/1 or  0.1 WL  and
short-term follow-up measurements were conducted  under  closed-
house conditions, an over-estimation of the  annual average
concentration may result.  However,  the EPA recommends  short-
term follow-up measurements in these situations  because an
additional 12 months of exposure could cause a significant
increase in health  risk.

     The average of the follow-up measurements made  in  the  two
different living areas in the home  are intended  for comparison
to guidance levels  given-  in terms of  annual  average  concentra-
tion.   Such guidance levels are discussed in the "Citizen's
Guide to Radon," published by  the EPA  Office of  Radiation
Programs and available through your EPA regional  office or your
State radiation  control office.  The following four paragraphs
are excerpted from  that document and  summarize the  EPA  guidance
for action based on the results  of  follow-up measurements.

      If the follow-up measurement  results are  about  1.0 WL  or
higher, or about  200 pCi/1  or  higher,  residents  should  be aware
 that  exposures  in  this range  are among the highest  observed  in
 homes and  should  undertake  action  to reduce levels  as far below
 1.0 WL  (200 pCi/1)  as  possible.  EPA recommends  that  action  be
 taken within  several weeks.   If  this is not possible, residents
 should  determine,  in consultation with appropriate  State  or
 local health  or radiation protection officials,  if  temporary
 relocation  is  appropriate until  the levels can be reduced.

      If the  follow-up  measurement  results are  about  0.1 to
 about  1.0  WL,  or about  20 to  about  200 pCi/1,  residents should
 be aware that  exposures  in this  range are considered  greatly
 above average  for  residential  structures, and  should  undertake
 action  to  reduce levels  as far below 0.1 WL (20 pCi/1)  as
 possible.   EPA recommends that such action be  taken within
 several months.

      If the  follow-up  measurement  results are  about 0.02  to
 about 0.1  WL,  or about 4  pCi/1 to  about 20 pCi/1, EPA advises
 that  exposures in this range are considered above average for
 residential  structures.   Residents  should undertake action to
 lower  levels  to about  0.02 WL (4 pCi/1) or below.  EPA
 recommends that residents take action within a few years,
 sooner if  levels are  at the upper end  of this range.
                                10

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     If the follow-up measurement reults are about  0.02 WL  or
lower,  or about 4 pCi/1 or lower, residents should  be aware
that exposures in this range are considered average  or  slightly
above average for residential structures.  Although  exposures
in this range do present some risk of lung cancer,  reductions
of levels this low may be difficult, and sometimes  impossible,
to achieve.

     Diagnostic measurements made to determine the  source of
radon influx into the house and to guide the choice  of
mitigation techniques are beyond the scope of this document.
However, since a follow-up measurement should be made before
the need for permanent mitigation is decided, a similar
follow-up measurement conducted after the mitigation work is
completed can be used as a benchmark to estimate the efficacy
of the  mitigation effort.
                              11

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4.   EXAMPLES OF APPROPRIATE MEASUREMENT  LOCATIONS

     The following  are  examples  of  locations  where screening
and follow-up measurements should be  made.

     1.  A split-level  house  is  built over  a  garage on the
         lowest level and has  a  den and  a bedroom built several
         feet higher  than the  garage, a  kitchen on a middle
         level over the  garage,  and bedrooms  on a level over
         the den  several feet  higher  than  the kitchen.  The
         screening  measurement should be made in the lowest
         bedroom  on the  floor  next  to the  garage.  The
         follow-up  measurement should be the  average of
         measurements made  in  that  same  lower bedroom and
         measurements made  in  one of  the upper bedrooms.

     2.  A farm house has an  uninhabitable  dirt-floor cellar,  a
         ground floor containing a  kitchen  and a living room,
         and an upper floor  containing bedrooms.  The screening
         measurement  should  be made in the  ground floor living
         room,  and  the  follow-up measurement  should be the
         average  of measurements made in the  same living room
         and measurements made in one of the  upper floor
         bedrooms.

     3.  A multi-story  apartment building  has a livable,
         finished basement  used as  a laundry  room.  The
         screening  measurement should be made in the basement,
         and  if  the results  warrant follow-up measurements,
         they  should  be made in the bedroom and living room of
         each  apartment unit.   If the source  of radon is
         believed to  be the underlying soil,  only the apartment
         units  on the lowest floors need to be tested.

      4.  A  one-story, no basement,  slab-on-grade house is
         tested  for radon.   The screening  measurement should be
         made  in a bedroom,  and the follow-up measurement
          should  consist of  measurements made  in a bedroom and
          the living room.
                                12

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5.  RECOMMENDED USES OF GRAB SAMPLING

     Short-term or grab sampling  techniques  can  be used to
measure concentrations of either  radon gas or  radon decay
products in the air.  Samples are  usually  acquired over a
5 or 10 minute sample period, which may  be considered  a
virtually instantaneous measurement when compared  with most
other measurement techniques commonly used in  homes.   While an
individual grab sample may be quite accurate  in  representing
the concentration of radon or radon decay  products at  the
moment of sampling, it is usually  a poor indicator of  the
long-term average concentration because  of the inherent
variability of the radon concentration in  homes.   For  this
reason, grab sample results should be interpreted  with
caution.  However, grab sampling  methods have  two  distinct
advantages over other measurement  techniques.  First,  grab
samples can produce results within a matter of minutes to
hours, enabling one sampling team  to test  and  produce  results
for several houses each day.  Second, the  conditions at the
time of measurement are known to  the sampler who must  be
present during the measurement and who can take  note of
unusual weather or other factors  that may  influence  the result.

     If grab samples are to be used, it  is important to
remember that, unlike the other measurement techniques,  the
results are greatly influenced by  conditions that  existed  in
the home for 8 to 12 hours prior to the  moment of  measurement.
The results of measurements made  in a tightly  closed home  will
differ significantly from the results of measurements  made  in
the same home after it has been thoroughly ventilated.  The
results of integrated measurements of at least 24  hours in
duration, however, are most influenced by conditions during the
measurement period.  It is therefore especially  important when
taking grab samples to make every  effort to conform  to  the
closed-house conditions for 12 hours before the measurement.

     Grab sampling has been particularly useful  in  situations
in which homes located near sites of known high concentrations
must be screened quickly.   Grab samples  are also very  useful as
diagnostic tools to trace the probable cause of elevated levels
in a home, although that application is  beyond the  scope of
this document.  Grab techniques  are not  recommended for
follow-up measurements, however,  because of their poor
correlation with long-term averages.

     Because of the high uncertainties associated with  the
short measurement duration,  the  results  of a  single grab sample
should not be used as the sole estimate  of average
concentrations upon which  a decision,  such as the need  for
remedial action, is based.
                               13

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6.  CLOSED-HOUSE CONDITIONS

     Short-term measurements used  for  comparison  to  guidance
levels should be made under closed-house conditions.   (Short-
term measurements are made over  a  shorter period  of  time  than
12 months and are not part of a  series  of four  measurements
made over a year's  time.)  Closed-house conditions  are
necessary for short-term measurements  to stabilize  the radon
and radon decay product concentrations  and  increase  the
reproducibility of  a measurement.   To  the extent  reasonable,
windows and external doors should  be kept closed  (except  during
normal entry and exit).  Normal  entry  and exit  includes a  brief
opening and closing of a door, but an  external  door  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 attic  and  window fans should
not be operating.   For measurement periods  of  3 days or less,
these conditions should exist for  12 hours  prior  to  beginning
the measurement.  It may be difficult  to verify these
conditions or to implement them  for an  extended period, but
they  should be  adhered to as  closely as possible.

      Closed-house 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 area,  this  can  be  the period
from  late fall  to early  spring.   In some houses,  the most
stable levels occur during  late  fall  and early spring, when
windows are kept closed  but the  home heating system (which
causes some ventilation  and circulation)  is not used.§  If
information about variations  of  indoor radon levels  i'n a
particular area is  available,  the  information  can be used to
choose a measurement  time when the radon concentrations are
highest and most  stable.

      We recommend  that measurements in northern climates  be
made  during  the winter season  for  two  major reasons.  First,
closed-house  conditions  exist  as normal living conditions, so
there is a fairly good assurance that  the  proper  conditions
will  exist prior  to and  during  the measurement period.  Second,
information  on  factors other  than  ventilation  rates  that
influence  indoor  radon  concentrations  indicate that concentra-
tions during  the winter  are generally  higher than during  the
summer.

      It may  be  necessary, however, to  make  measurements in
northern  climates  during  the  summer, when  closed-house
conditions  are  not  the  normal  living conditions.   It will then
be necessary  to establish  some means for providing  reasonable
assurance  that  closed-house  conditions exist prior  to and
during  the measurements.
                                14

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     Organizations 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-house conditions
normally exist.  If such times can be identified,  that  is  when
measurements should be conducted.   Air conditioning  systems
that recycle interior air can be operated during the closed-
house conditions if radon measurements are  being made.   Home
owners should be aware that any air circulation system  can
drastically alter the radon decay product concentration  without
significantly changing the radon concentration.

     Measurements lasting a few days or less should not  be
conducted if severe storms with high winds  are predicted.
Severe weather will affect the measurement  results in the
following ways.  First, a high wind will increase  the
variability of radon concentration because  of wind-induced
differences in air pressure between the house interior and
exterior.  Second, rapid changes in barometric pressure
increase the chance of a large difference in the interior  and
exterior air pressures, therefore  changing  the rate of radon
influx.  The rate of radon released from the ground is also
affected.  Weather predictions available on local news stations
should be sufficient to determine  if this criterion is
satisfied.

     A measurement made over 12 months,  whether it is an
integrated  measurement or a series of measurements, provides
information about the average concentrations during an entire
year, so the closed-house conditions do  not have to be
satisfied for annual average measurements.
                               15

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7.  INSTRUMENT SELECTION

     There are several different  measurement  systems  that  may
be used to determine the  radon  or  radon  decay product  concentra-
tions in houses.   In practice,  the choice  of  a system  is  often
dictated simply by availability -- if  an adequate  system  is
available, you use it.   If  alternative systems are available,
then the cost or the duration of  the measurement may  become  the
deciding factor.   EPA has developed measurement protocols  for
seven different systems  (EPA86),  and the Agency believes  that
any of  these  systems, when  used in accordance with the guidance
in that protocol document,  can  produce valid  results.   This
does not mean that all such measurements will produce  results
with identical uncertainties, but  rather that any  of  the  listed
systems is capable of producing adequate results  for  screening
or follow-up  purposes.   Each system has  its  own advantages and
disadvantages, however,  and the user must  exercise some
judgment in selecting the system best  suited  to the individual
situation.  The following sections detail  the characteristics
of the  seven  systems, pointing  out some  of the advantages  and
disadvantages of  each one.   This summary is  not exhaustive but
is intended to guide  the user  in making  an informed selection
of a measurement  system.

7.1  Continuous Radon Monitors  (CRM) or Continuous Working Level
     Monitors CCWLM):

     These  two  types  of  measurement systems  are similar in that
they use  an electronic  detector to accumulate and  store
information  related  to  the  periodic (usually hourly)  average
concentration of  radon  gas  or radon decay  products.  They are
installed  in  the  house,  turned  on or programmed for the desired
operating  time,  and  then left to operate for the programmed
time.

Advantages:

      o   Relatively short measurement  duration (minimum of 6
          hours  for screening, 24 hours for follow-up
          measurements).

      o   Hourly results  can track  the variation of concentra-
          tions  in the house.

      o   Most models have  small precision errors.

      o   Results  are available onsite.

 Disadvantages:

      o   Costly (each unit  may cost from $2500 to $10,000,
          depending on model).
                                16

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     o   Some models are heavy and awkward  to  move.

     o   Requires extensive calibration  in  a  radon calibration
         chamber.

     o   Requires a trained operator.

7.2  Alpha-Track Detectors

     Alpha-track detectors consist of  a  small  sheet  of  a
special plastic material.  The material  is  permanently  marked
when exposed to alpha particles,  such  as  those  emitted  by the
decay of radon or some of the short-lived radon  decay
products.  The detectors are usually in  a filtered container
that serves to make the measurement specific for  radon  gas.
They are installed in the home and left  for periods  of  up to 1
year.  At the end of that period, they must be  returned to  a
laboratory for processing and analysis.

Advantages:

     o   Relatively low cost per  detector.

     o   Convenient to handle and install.

     o   Unobtrusive when installed.

     o   No special skills required for deployment.

     o   Can be distributed by mail.

     o   Completely passive, needs no external power.

     o   Can measure the integrated average concentration over
         a 12-month period, which is the optimal measure  of
         long-term concentration.

Disadvantages:

     o   Relatively long measurement period necessary (3  months
         recommended minimum for currently available detectors)

     o   Large inherent variability (precision errors)
         particularly at low concentrations if the area of  the
         detector that is counted is small.
                               17

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7.3  Charcoal Canisters

     Charcoal canisters  are  small,  flat  containers  filled  with
a measured amount of activated  charcoal.   The  top  is  often
perforated or screened to  keep  the  charcoal  from falling  out,
and the container is covered with an  airtight  seal  when the
canister is not being used for  measurement.   Some  systems  now
use a filter bag to contain  the  charcoal.  The canisters  are
usually obtained from a  supplier and  are typically  left in
place for 2 to  7 days, resealed,  and  returned  to the  supplier
or analytical laboratory for evaluation.   Analysis  usually
consists of counting the gamma  radiation emission  rate  from  the
radon decay products resulting  from the  radon  adsorbed  on  the
charcoal.

Advantages:

     o   Low cost per canister.

     o   Convenient to handle and install.

     o   Unobtrusive when installed.

     o   No  special skills needed for deployment.

     o   Can be distributed  by  mail.

     o   Completely passive, needs  no external power.

     o   With proper  analysis,  can  yield precise results.

 Disadvantages:

     o   Some  canister  types are sensitive to temperature  and
         humidity.

     o   The  charcoal  adsorption technique is inherently
         limited  to a  few days  of sampling,  which  makes a
         longer term  measurement impossible  with a single
         detector.

 7.4  Radon  Progeny  Integrating  Sampling  Units (RPISU)

     The RPISU  is  a  radon decay product  measurement system
 consisting  of  a low  flow-rate  air pump that  pulls  air
 continuously  through  a  detector assembly containing a
 thermoluminescent  dosimeter  (TLD).   The  unit is operated  for
 periods  of  100  hours  or  longer.  At the  end  of that time  the
 unit  is  removed,  and  the detector assembly is returned  to the
 analytical  laboratory.   The  analysis consists of measuring the
 light  given off by  the TLD during heating.
                                18

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Advantages:

     o   Measures radon decay product  concentration directly.

     o   Relatively short measurement  period.

     o   The detector assembly  (not  the  entire  unit)  can be
         sent by mail.

     o   There is extensive experience in  the use  of  RPISUs,
         and measurement errors are well established.

Disadvantages:

     o   The entire unit may be both heavy  and  awkward  to move-

     o   May be limited to location with a.c. power.

     o   Significant capital cost per  unit  ($500-$3,000)
         and for the readout system ($5,000-$10,000).

     o   Units must be installed and picked up  by  trained
         personnel.

     o   Proper operation may be affected by high
         concentrations of airborne particulates,  such
         as those caused by smoking.

7.5  Grab Sampling

     Grab sampling consists of taking  a  small sample  of  air  from
the home and analyzing the radon or radon decay product  concen-
tration it contained.   The radon grab  sample is collected in a
special flask containing 100 to 2000 cubic centimeters of air.
The radon decay product grab sample consists of particulates
collected on a small filter.  Both samples can be  acquired
simultaneously with some systems.   The samples  should be  taken
in accordance with guidelines in the protocols and evaluated
according to standard procedures using an electronic
scintillation counting system.

Advantages:

     o   Results are quickly obtained.

     p   Equipment can be portable.

     o   Can measure both radon and its decay products
         simultaneously.
                               19

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     o   Can acquire and evaluate several samples per day.

     o   Conditions during the measurement are known to  the
         sampler.

Disadvantages:

     o   Very short measurement period may not be
         representative of long-term average.

     o   Requires a skilled operator.

     o   Requires careful control of house conditions
         for  12 hours before  the measurement.

     o   System cost is $2,500 to $10,000.
                                20

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                            References
Ch74
EPA86
DOES 6
DOE87
F184
Geo84
Go83
He85
Ke84
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                               21

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                                22

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