Current through Register Vol. 48, No. 12, March 22, 2024
a)
Quality Assurance
1) Professional licensees
providing measurement services using radon and radon product measurement
devices shall establish and maintain a Quality Assurance Program (QAP). These
programs shall include written procedures for attaining quality assurance
objectives and a system for recording and monitoring the results of the quality
assurance measurements for each device used. The QAP shall include the
maintenance of control charts and related statistical data.
2) The objective of quality assurance is to
ensure that data are scientifically sound and of known precision and accuracy.
This subsection (a)(2) discusses the 6 general categories of quality control
measurements. Specific guidance is provided for each method in the relevant
protocol.
A) Calibration Measurements.
Calibration measurements are samples collected or measurements made in a known
radon environment, such as a radon chamber. Instruments providing immediate
results, such as continuous working level and radon monitors, shall be operated
in a radon chamber to establish individual instrument calibration factors.
i) 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.
ii) Determination of these calibration
factors is a necessary part of the laboratory analysis and is the
responsibility of the laboratory. These calibration measurement procedures,
including the frequency of tests and the number of devices to be tested, shall
be specified in the QAP maintained by manufacturers and analysis
laboratories.
iii) Licensees
providing measurements with active devices are required to recalibrate their
instruments at least once every 12 months.
B) Known Exposure Measurements (Spikes).
Known exposure measurements or spiked samples consist of detectors that have
been exposed to known concentrations in a radon chamber. These detectors, such
as charcoal canisters, alpha track detectors and electret ion chambers, are
labeled and submitted to the laboratory in the same manner as ordinary samples
to preclude special processing.
i) Suppliers
and analysis laboratories shall provide for the blind introduction of spiked
samples into their measurement processes and the monitoring of the results in
their QAP.
ii) Licensees using
passive monitorsshall conduct spiked measurements (i.e., exposure in a radon
chamber where the environmental radon level is controlled) to aid the Agency in
verifying the accuracy of the entire measurement system. The licensee shall
conduct 3 spiked measurements per 100 measurements, with a minimum of 3 spiked
measurements per year. For example, a licensee conducting only 70 measurements
in a year must conduct at least 3 spiked measurements. A licensee conducting
500 measurements during a one-year period must conduct at least 15 spiked
measurements (3 per each 100). No more than 6 spiked measurements will be
required to be taken within any single month. For example, a licensee
performing more than 200 measurements in one month is not required to perform
more than 6 spiked measurements that month. Licensees are encouraged to take
their spiked measurements from multiple batches when possible and to take more
than the minimally required spiked measurements at their discretion. Devices
shall be exposed in a radon chamber at a minimum of 3 different radon
concentrations, such as approximately 4.0, 10-30 and 30-100 pCi/L.
iii) Spikes shall be labeled in the same
manner as field detectors to ensure identical processing. The results of
analyses of detectors exposed to known radon concentrations shall be monitored
and recorded. Any significant deviation from the known concentration to which
they were exposed shall be investigated and corrective action taken.
C) Background Measurements.
Background measurements are required both for continuous monitors and for
passive detectors requiring laboratory analysis.
i) Licensees using continuous monitors shall
perform sufficient instrument background measurements to establish a reliable
instrument background and to act as a check on instrument operation.
AGENCY NOTE: Calibration laboratories routinely perform
background measurements of continuous monitors during the calibration of
instruments.
ii) Passive
detectors requiring laboratory analysis require one type of background
measurement made in the laboratory and another in the field.
iii) Laboratories shall measure 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 (by the
laboratory) from the field sample results reported to the user, and shall be
made available to the users for quality assurance purposes.
iv) Laboratories performing these
measurements shall calculate the lower limit of detection (LLD) for their
measurement systems. 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.
v) Licensees
using passive detectors shall employ field controls (called blanks) equal to
approximately 5 percent of the detectors that are deployed, or 25 each month,
whichever is smaller.
vi) These
controls shall 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. The results shall be monitored and
recorded.
vii) 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 and is discussed in the protocol for each method.
D) Duplicate Measurements. Duplicate
measurements provide a check on the precision 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 or improper data transcription or
handling by suppliers, laboratories, or technicians performing placements.
Precision error can be an important component of the overall error; therefore,
licensees performing measurements shall monitor precision.
i) Duplicate measurements shall 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 duplicate measurement shall be distributed systematically
throughout the entire population of samples.
ii) The precision of duplicate measurements
shall be monitored and recorded in the quality assurance records. The analysis
of data from duplicates shall be plotted on range control charts. If the
precision estimated by the user is not within the precision expected of the
measurement method, the cause of the problem shall be investigated.
iii) Detectors shall be treated identically
in every respect. They shall be shipped, stored, opened, installed, removed and
processed together, and not identified as duplicates to the processing
laboratory.
E) 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 include the frequent
use of an instrument check source. Components of the device (such as a pump,
battery or electronics) shall be checked regularly and the results noted in a
record. Each user shall develop methods for regularly monitoring (preferably
daily with use) their measurement system and for recording and reviewing
results.
F) Cross-checks.
Professional licensees using active monitors shall check their monitors for
bias on a regular basis. Ideally, such measurements are made in a radon
chamber. Exposure in a radon chamber is required during calibration. It can be
difficult to expose active monitors more often than once every 12 months. It is
important to more frequently assess the continued satisfactory operation of the
instrument response and to ensure damage from shipping has not occurred prior
to an instrument being placed into service after calibration. Cross-checks
shall be performed prior to placing an instrument being returned to service
after calibration and at 6 months (plus or minus a month) after calibration.
The following conditions shall be met:
i)
Where feasible, a cross-check shall begin with an instrument background
measurement.
ii) The cross-check
measurement shall be made in an environment that has been chosen for its
stability and radon concentration that is above the lower limit of
detection.
iii) Cross-checks shall
be side-by-side measurements.
iv)
One of the instruments shall have been calibrated within the last 45
days.
v) A measurement of at least
48 hours duration shall be conducted.
vi) The bias of cross-check measurements
shall be monitored and recorded in the quality assurance records. If the bias
estimated by the user is not within the bias expected of the measurement, the
cause of the problem shall be investigated and corrective action taken in
accordance with the licensee's Agency-approved QAP.
b) Protocol for using
continuous radon monitors (CRs) to measure indoor radon concentrations
1) Refer to Section
422.130 for
a list of general conditions that shall be met and standard information that
shall be documented.
2) When
performing a radon measurement, the CR shall be programmed to run continuously,
recording periodically (hourly or more frequently) the radon concentration for
at least 48 hours. Longer measurements may be required per the continuous
monitor type and the radon level being measured.
3) If the first 4 hours of data from a
48-hour measurement are discarded because data are produced prior to the
establishment of equilibrium conditions in the test device, the remaining hours
of data shall be averaged and shall be sufficient to represent a 2-day
measurement.
4) Every CR shall be
calibrated in a radon chamber, approved by the Agency, before being placed into
service, and after any repairs or modifications that could affect the
calibration. Subsequent recalibrations and background checks shall be performed
at least once every 12 months. Each scintillation cell requires an individual
calibration factor.
5) Background
measurements shall be performed after every 1,000 hours of operation of
scintillation cell-type CRs and whenever any type of CR is calibrated. The
background shall be checked by purging the monitor with clean, aged air or
nitrogen in accordance with the manufacturer's instructions. In addition, the
background count rate shall be monitored in accordance with the manufacturer's
instruction.
6) Licensees providing
measurement services with CR devices shall perform duplicate measurements. The
performance and analysis of duplicates shall be completed in accordance with
subsection (a)(2)(D).
7) Pumps and
flow meters shall be checked before and after each measurement in accordance
with the manufacturer's instruction.
8) Licensees providing measurement services
with CR devices shall perform cross-checks. The performance and analysis of
cross-checks shall be completed in accordance with subsection
(a)(2)(F).
c) Protocol
for using alpha track (AT) detectors to measure indoor radon concentrations
1) Refer to Section
422.130 for
a list of general conditions that shall be met and standard information that
shall be documented.
2) The
laboratory background level for each batch of ATs shall be established by each
laboratory licensed by the Agency. Laboratories shall measure the background of
a statistically significant number of unexposed ATs that have been processed
according to the licensee's Quality Assurance Program implementing/operating
procedures.
3) Every AT laboratory
system shall be calibrated in a radon chamber at least once every 12 months.
Determination of a calibration factor requires exposures of ATs to a known
radon concentration in a radon chamber. These calibration exposures shall be
used to obtain or verify the conversion factor between net tracks per unit area
and radon concentration.
A) ATs shall be
exposed in a radon chamber at a minimum of 3 different radon concentrations
such as approximately 4.0, 10-30 and 30-100 pCi/L or exposure levels similar to
those found in the tested buildings.
B) Expose a minimum of 10 detectors at each
radon concentration of the chamber.
C) A calibration factor shall be determined
for each batch or sheet of detector material received from the supplier.
Alternatively, calibration factors may be established for several sheets, and
these factors extended to detectors from sheets exhibiting similar
sensitivities (within pre-established tolerance limits).
D) Analysis instruments shall be checked at
least daily for operability prior to operation. Analysis instruments do not
need to be checked on days not used.
4) Licensees providing measurement services
with AT devices shall perform known exposure measurements (spikes). The
performance and analysis of spikes shall be completed in accordance with
subsection (a)(2)(B).
5) Licensees
providing measurement services with AT devices shall perform duplicate
measurements. The performance and analysis of duplicates shall be completed in
accordance with subsection (a)(2)(D).
6) Licensees providing measurement services
with AT devices shall perform background measurements. The performance of
background measurements shall be completed in accordance with subsection
(a)(2)(C).
A) The results shall be monitored
and recorded. If one or a few field blanks have concentrations significantly
greater than the LLD established by the supplier, it may indicate defective
packaging or handling and the licensee shall investigate the cause. If the
average value from the field control devices (field blanks) is significantly
greater than the LLD established by the supplier, this average value shall be
subtracted from the individual values reported for the other devices in the
exposure group.
B) It may be
advisable to use 3 sets of detectors (pre-exposure, field and post-exposure
background) in order to allow the most thorough and complete evaluation of
radon levels. For example, one group of detectors (pre-exposure detectors) may
be earmarked for background measurement and returned for processing immediately
after the other detectors are deployed. The results from these detectors
determine if the number of tracks acquired before deployment is significant and
should be subtracted from the gross result. The second set of background
detectors (post-exposure background detectors) are obtained just before the
field monitors are to be collected and are opened and kept in the same location
as the returning field monitors for the same duration, and returned with them.
Finally, this "post-exposure background" is subtracted from the field results,
if found to be significant. In general, a value of 1 pCi/L or greater for any
blank AT indicates a significant level that should be investigated and
potentially subtracted from the field AT results.
d) Protocol for using electret ion
chamber radon (ES or EL) detectors to measure indoor radon concentration.
1) Refer to Section
422.130 for
a list of general conditions that shall be met and standard information that
shall be documented.
2) Every
short-term and long-term electret system and the electret reader(s) shall be
calibrated in a radon chamber, approved by the Agency. Initial calibration for
the system is provided by the manufacturer. Subsequent recalibrations shall be
performed at least once every 12 months. Determination of calibration factors
for short-term or long-term detectors requires exposure of detectors to known
concentrations of radon-222 in a radon exposure chamber. Since short-term and
long-term electret detector systems are also sensitive to gamma radiation, a
gamma exposure rate measurement in the test chamber is also required
annually.
3) The following is
provided to manufacturers and suppliers of ES or EL services as minimum
requirements in determining the calibration factor:
A) Detectors shall be exposed in a radon
chamber at a minimum of 3 different radon concentrations, such as approximately
4.0, 10-30 and 30-100 pCi/L, or exposure levels similar to those found in the
tested buildings.
B) Expose a
minimum of 10 detectors at each radon concentration of the chamber.
C) Ensure a period of exposure sufficient to
allow the detector to achieve equilibrium with the radon chamber
atmosphere.
4) Licensees
providing measurement services with ES or EL devices shall perform known
exposure measurements (spikes). The performance and analysis of spikes shall be
completed in accordance with subsection (a)(2)(B).
5) Licensees providing measurement services
with ES or EL devices shall perform duplicate measurements. The performance and
analysis of duplicates shall be completed in accordance with subsection
(a)(2)(D).
6) Licensees providing
measurement services with short-term or long-term electrets shall set aside a
minimum of 5 percent of the electrets or 10, whichever number is smaller, from
each shipment and evaluate them for voltage drift. The electrets shall be kept
covered with protective caps in a low radon environment and analyzed for
voltage drift over a time period similar to the time period used for those
deployed in measurements. Any voltage loss found in the control electrets of
more than one volt per week over a 3-week test period for short-term electrets,
or one volt per month over a 3-month period for long-term electrets, shall be
investigated.
7) Proper operation
of the surface voltmeter shall be monitored following the manufacturer's
procedures for zeroing the voltmeter and analyzing a reference electret. These
checks shall be conducted at least once a week while the voltmeter is in
use.
8) All Laboratory Analysis
licensees providing recharging services of short-term or long-term electrets
shall only provide those services for devices they manufacture or for devices
for which they have written authorization from the manufacturer.
e) Protocol for using activated
charcoal adsorption (AC) devices to measure indoor radon concentrations
1) Refer to Section
422.130 for
a list of general conditions that shall be met and standard information that
shall be documented.
2) Every
activated charcoal adsorption system shall be calibrated in a radon chamber at
least once every 12 months. Determination of calibration factors for ACs
requires exposure of the detectors to known concentrations of radon-222 in a
radon chamber. The calibration factors depend on the exposure time and may also
depend on the amount of water adsorbed by the charcoal container during
exposure. Calibration factors shall be determined for each AC measurement
system (container type, amount of charcoal, gamma detector type,
etc.).
3) Licensees providing
measurement services with AC devices shall perform known exposure measurements
(spikes). The performance and analysis of spikes shall be completed in
accordance with subsection (a)(2)(B).
4) Licensees providing measurement services
with AC devices shall perform duplicate measurements. The performance and
analysis of duplicates shall be completed in accordance with subsection
(a)(2)(D).
5) Laboratory Control
Detectors. The laboratory background level for each batch of ACs shall be
established by each laboratory or supplier. Suppliers shall measure the
background of a statistically significant number of unexposed detectors that
have been processed according to their standard operating procedures
(laboratory blanks). The analysis laboratory or supplier calculates the net
readings, that are used to calculate the reported sample radon concentrations,
by subtracting the laboratory blank values from the results obtained from the
field detectors.
6) Licensees
providing measurement services with AC devices shall perform background
measurements. The performance of background measurements shall be completed in
accordance with subsection (a)(2)(C).
A) One
or a few of the field blanks have concentrations significantly greater than LLD
established by the supplier may indicate defective devices or poor procedures
and the licensee shall investigate the cause.
B) If most of the field blanks have
concentrations significantly greater than the LLD, the average value of the
field blanks shall be subtracted from the reported field detector
concentrations and the supplier notified of a possible problem.
7) Counting equipment shall be
subject to daily operability checks by counting an instrument check source and
determining whether the reference source is constant to within established
limits (2 standard deviations). Daily operability checks do not need to be
performed on days the instrument is not used. The characteristics of the check
source (geometry, type of radiation emitted, etc.) shall be similar to those of
the samples analyzed. The count rate of the check sources shall be high enough
to yield good counting statistics in a short time (for example, 1000 to 10,000
counts per minute) to provide a maximum random uncertainty of 5
percent.
f) Protocol for
using charcoal liquid scintillation (LS) devices to measure indoor radon
concentrations
1) Refer to Section
422.130 for
a list of general conditions that shall be met and standard information that
shall be documented.
2) Every LS
laboratory system shall be calibrated in a radon chamber at least once every 12
months. Determination of calibration factors for LS devices requires exposure
of calibration devices to known concentrations of radon-222 in a radon chamber
at carefully measured radon concentrations. The calibration factors depend on
the exposure time and may also depend on the amount of water adsorbed by the
device during exposure. Calibration factors shall be determined for a range of
different exposure times and, as appropriate, humidities.
3) Licensees providing measurement services
with LS devices shall perform known exposure measurements (spikes). The
performance and analysis of spikes shall be completed in accordance with
subsection (a)(2)(B).
4) Licensees
providing measurements services with LS devices shall perform duplicate
measurements. The performance and analysis of duplicates shall be completed in
accordance with subsection (a)(2)(D).
5) Laboratory Control Devices. The laboratory
background level for each batch of LS devices shall be established by each
laboratory or supplier. Suppliers shall measure the background of a
statistically significant number of unexposed LS devices that have been
processed according to their standard operating procedures (laboratory blanks).
The analysis laboratory or supplier calculates the net readings, that are used
to calculate the reported sample radon concentrations, by subtracting the
laboratory blank values from the results obtained from the field
detectors.
6) Licensees providing
measurement services with LS devices shall perform background measurements. The
performance of background measurements shall be completed in accordance with
subsection (a)(2)(C).
A) One or a few of the
field blanks have concentrations significantly greater than the LLD established
by the supplier may indicate defective devices or poor procedures and the
licensee shall investigate the cause.
B) If most of the field blanks have
concentrations significantly greater than the LLD, the average value of the
field blanks shall be subtracted from the reported field detector
concentrations and the supplier notified of a possible problem.
7) Counting equipment shall be
subject to daily operability checks by counting an instrument check source and
determining whether the reference source is constant to within established
limits (2 standard deviations). Daily operability checks do not need to be
performed on days the instrument is not used. The characteristics of the check
source (geometry, type of radiation emitted, etc.) shall be similar to those of
the samples analyzed. The count rate of the check sources shall be high enough
to yield good counting statistics in a short time (for example, 1000 to 10,000
counts per minute) to provide a maximum random uncertainty of 5
percent.
g) Protocol for
using continuous working level (CW) monitors to measure indoor radon progeny
concentrations
1) Radon Decay Product
measurements may be appropriate under certain conditions in large buildings,
but are not currently routinely performed by licensees or recommended by the
American Association of Radon Scientists and Technologists. The Agency does not
recommend their use for home environment or residential real estate
measurements. Licensees interested in using CWs for measurement purposes shall
submit Standard Operating Procedures, consistent with this Part, specific to
the model and design of the CW instrument to the Agency for approval.
2) Conditions and information in Section
422.130
shall be met.
3) Any measurement
result based on radon progeny shall be reported to no more than 3 decimal
places, e.g., 0.033 working level (WL).
4) The integrated average WL over the
measurement period shall be reported as the measurement result.
5) When performing a radon measurement, the
CW shall be programmed to run continuously, recording the periodic WL and, when
possible, the total integrated average WL. The longer the operating time, the
smaller the uncertainty associated with using the measurement result to
estimate a longer-term average concentration.
6) Working level values shall be converted to
pCi/L and both shall be reported to the client. The conversions from WL to
pCi/L shall be presented and explained clearly in the report to the client. A
statement shall be included in the measurement report that this approximate
conversion is based on a 40 percent equilibrium ratio. In addition, the report
shall state that this equilibrium ratio is typical, but that any indoor
environment may have a different and varying relationship between radon and
radon progeny.
7) Every continuous
WL monitor shall be calibrated in a radon chamber, approved by the Agency,
before being placed into service and after any repairs or modifications that
could affect the calibration. Subsequent recalibrations shall be performed at
least once every 12 months.
8)
Background measurements shall be performed after every 168 hours of operation
and whenever the unit is calibrated. The CW shall be purged with clean, aged
air or nitrogen in accordance with the manufacturer's instructions. In
addition, the background count rate may be monitored more frequently by
operating the CW in a low radon concentration.
9) Measurement licensees providing
measurement services with CW devices shall perform duplicate measurements. The
performance and analysis of duplicates shall be completed in accordance with
subsection (a)(2)(D).
10) Pumps and
flow meters shall be checked before and after each measurement in accordance
with the manufacturer's instruction to ensure accuracy of volume measurements.
This may be performed using a dry-gas meter or other flow measurement device of
traceable accuracy.
11) Licensees
providing measurement services with CW devices shall perform cross-checks. The
performance and analysis of cross-checks shall be completed in accordance with
subsection (a)(2)(F).