MS-QA_06-2019 rev5

ANSI/AARST MS-QA 2019 16 Radon Measurement Systems Quality Assurance Field Operations—EIC, Alpha Track and Charcoal Adsorption 5.2.1 Field Operation Blanks—Distribution Blanks are to be distributed among all the environments where the devices are handled, stored and transported. Therefore, careful logging of location and time for all detectors used as blanks is required. a) Field Blanks A portion of the required 5% blanks shall be field blanks with additional blanks dedicated, if and where deemed necessary, to other evaluations such as for storage, office or trip blanks . Field blanks verify that there have been no unexpected influences during all conditions within the chain of custody. Therefore, field blanks are to be handled and placed exactly as the routine devices used for testing, except that the blanks are not used to measure radon concentration. Each field blank is to be carried through all steps in the measurement process, which, depending on the configuration of the device and seal, may include opening and immediately resealing the detector and may include doing so in the environment being tested. b) Office/Storage Blanks Office blanks verify that there were no influencing factors that occurred during storage or in-office handling. If CAD or ATD inventories are stored in a low-radon environment, RH extremes are recorded, and this information is documented and available upon request to auditors, then office blanks need not be used, as long as this is consistent with the manufacturer’s directions. Otherwise, CAD and ATD users who cannot store devices in a monitored environment are responsible for setting aside at least approximately 5% of their devices (or as directed by the QA manager) as storage blanks . c) Lab-Transit Blanks Transit (or “trip”) blanks verify and document the lack of influences during shipping. Informative advisory —Measurement providers should follow manufacturer’s instructions regarding how to conduct each type of blank . 5.2.3 Control Limits for Field Operation Blanks The evaluation is to identify any detectable concentration or signal that is above the measurement systems minimum detectable concentration (MDC). If blank results indicate concentrations greater than the MDC, as presented in Table 5.2 , then an investigation shall be conducted in consultation with the analysis laboratory. Table 5.2 Control Limits for Blanks Method Control Limit Action CAD and ATD methods > MDC Investigate, document and, if necessary, take corrective action EIC Methods ≥ 2 volts, or as recommended by the manufacturer for that configuration