ILLINOIS REGISTER 6844
ILLINOIS EMERGENCY MANAGEMENT AGENCY
NOTICE OF PROPOSED AMENDMENTS
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
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,
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