MS-QA_06-2019 rev5

ANSI/AARST MS-QA 2019 13 Radon Measurement Systems Quality Assurance Continuous Radon Monitors (CRM) 4.2.3 CRM Comparison Check—Warning and Control Limits In all cases, warning and control limits shall be equal to or more stringent than: a) If the average of the two measurements is ≥ 4.0 pCi/L, the default interim QC limits for the CRM are based upon an “ in-control ” expected deviation of an RPD of up to 14%. — The warning limit indicating a potential problem requiring investigation is triggered when an RPD > 28.0%. — The control limit indicating a potentially serious problem is triggered when an RPD > 36%, and if the control limit is reached the measurement system shall be subject to corrective action and probable recalibration. b) If the average of the two measurements is ≤ 4 pCi/L (150 Bq/m 3 ), but ≥ 2 pCi/L (75 Bq/m 3 ), the QC limits are based on an “ in-control ” expected deviation an RPD of up to 25%. — The warning limit indicating a potential problem requiring investigation is triggered when an RPD > 50%. — The control limit indicating a potentially serious problem is triggered when an RPD > 67%. c) If the average of the two measurements is less than 2 pCi/L, the criterion is met if the absolute value of the difference between the two results is less than 1.0 pCi/L, or both results are less than the minimum detectable concentration (MDC). Note—These minimum requirements are presented for those who do not yet have sufficient QC data to develop more stringent limits specific to their measurement systems in accordance with the guidance in the MS-QA Companion Guidance Section B or another statistically defensible control limit generation algorithm, as informed by their field experience. Table 4.1: Criterion for CRM Comparison Checks (Duplicates if identical systems) Average Concentration Warning Limit RPD Control Limit RPD ≥ 4.0 pCi/L ( ≥ 150 Bq/m 3 ) 28.0% 36.0% < 4.0 and ≥ 2.0 pCi/L (< 148 and ≥ 75 Bq/m 3 ) 50.0% 67.0% < 2.0 pCi/L (< 75 Bq/m 3 ) n/a Absolute value of the difference between the results ≤ 1.0 pCi/L (37 Bq/m 3 ), or both are less than the MDC 4.3 CRM Calibration 4.3.1 CRM Calibration—Frequency and CRM Calibration System (Chamber) Each CRM is to be calibrated at least annually in a calibration facility that meets the requirements of a standard test atmosphere for radon as defined in this standard. 4.3.2 CRM Calibration—Exposure Duration Calibration durations shall be 24 hours or longer, starting after the radon and decay product concentrations in the detection volume of the instrument have reached equilibrium and the device has reached count-rate equilibrium (typically 4 hours after the device exposure begins and as indicated by the operating instructions) and for a duration consistent with the manufacturer’s instructions. Sufficient counts need to be accrued during the calibration exposure to ensure that the uncertainty due to few counts (i.e., counting statistics) are not the largest component of uncertainty.