MS-QA_06-2019 rev5

ANSI/AARST MS-QA 2019 3 Radon Measurement Systems Quality Assurance Definitions concentration, temperature and relative humidity in the surrounding air. This class of device can provide an accurate representation of the average radon concentration during the exposure period if there are no large changes in radon concentration or the environment (e.g., temperature, humidity) during the exposure. Because of the half-life of radon and the time it takes for radon to adsorb, they are typically limited to exposure durations from 2 to 7 days. Calibration of a charcoal adsorption system is accomplished through exposures of representative sets of devices in a STAR for various time periods and different temperatures and humidities. Coefficient of Variation (CV): The sample standard deviation(s) of a set of measurements expressed as a percentage of the arithmetic mean of the measurements; CV = 100 (s/mean). Collocated : Two or more detectors or instruments that are operated simultaneously while located side by side, separated by a distance that is large enough to preclude the air sampled by any of the devices from being affected by any of the other devices but small enough so that all devices measure air that is equally representative of the general area in which the devices are located (U.S. EPA 2017). Comparison Checks: Collocated, simultaneous measurements conducted for the purpose of assessing and monitoring measurement reliability. Comparison checks include but are not limited to duplicate measurements that are defined as collocated, simultaneous measurements using measurement devices of the same manufacturer, model, and most recent calibration date and facility. Continuous Radon Monitor (CRM): An electronic device that (1) is capable of automatically recording a retrievable time series of numeric measurements of radon concentration averaged over time intervals of 1 hour or less; (2) has a minimum detectable concentration (MDC) of no greater than 148 Bq/m 3 (4 pCi/L) for a 1-hour measurement; and (3) has a calibration factor of at least 2 counts per hour per 37 Bq/m 3 (0.054 counts per hour [cph] per Bq/m 3 or 2 cph per pCi/L). Corrective Action : Actions taken to identify and eliminate root causes of a problem thus preventing their recurrence. Note—It is important to recognize that some failed QC results, especially those near the limits, may occur solely by chance and not be due to a correctible problem. In such cases, repeated QC checks will be within limits, and no corrective action is needed. Corrective action may include communicating with instrument providers, the analysis laboratory and shippers (as relevant) to find and fix the cause of poor measurement performance, as well as thorough documentation of the problem, the solution and preventive action. Failed QC checks may indicate a problem with already-completed measurements, and corrective action in that case may include retesting environments where previous measurements are not defensible. Corrective action records document how the results of QC checks were used to validate or invalidate measurements already conducted with that measurement system. Data Validation: Valid data are produced when a measurement system, including storage, field deployment, transport, analysis and reporting, are operating “ in-control ” and within QC limits, and in-control QC checks demonstrate stable operation both before and after a set of validated data. Duplicate Measurements: Collocated , simultaneous measurements conducted with instruments or devices that are identical (including manufacturer, model, and, for continuous monitors, the same most recent calibration facility and schedule) for the purpose of assessing and monitoring the measurement system imprecision. (See Comparison Check for a different category of QC measurements that do not require the use of identical devices.) Electret Ion Chamber (EIC) Method: This type of device uses an ion chamber made of, or lined with, an electrically conductive material with an electret as the detecting mechanism. The surface voltage of the