MS-QA_06-2019 rev5

ANSI/AARST MS-QA 2019 20 Radon Measurement Systems Quality Assurance EIC Analysis 6.3.2 EIC Analysis—Detector Transport and Storage Informative advisory —Electret surfaces should be exposed to a minimum of air volume except when the electrets are used to measure radon concentrations or are being analyzed, and the period of exposure to air when assembling or analyzing electrets is to be as brief as possible. 6.3.3 EIC Analysis—Timely Transport or Shipping for Analyses Transport, shipping and handling must be arranged so that the initial pre-test surface voltage is measured not more than 7 days prior to the beginning of the exposure, and the final surface voltage is measured not more than 7 days after the end of exposure. Exceptions to these durations are acceptable if agreed upon between the analyst and the manufacturer. 6.3.4 EIC Analysis—Electret Voltage Drift All new electrets are to be inspected and their voltage measured upon receipt. Any electrets with initial voltage that is less than manufacturer’s specifications are to be returned to the manufacturer. For the voltage drift evaluation: a) The initial voltage and the serial number of each new electret are to be recorded in QA logs, and at least 5% of all new electrets (including 5% of each electret type) shall be randomly chosen for voltage drift tests. b) All electret surfaces are to be kept covered with protective caps or other mechanisms to minimize exposure to air during the voltage drift tests. c) The voltage drift of each of the electrets used for short-term testing should be measured over a period of at least 4 weeks and are to exhibit an average voltage drop of no more than 6 volts per month or as specified by the manufacturer. d) The voltage drift of the electrets used for long-term testing should be measured over a period of at least 3 months and are to exhibit voltage loss of no more than 4 volts per month or as specified by the manufacturer. e) Any voltage loss measured in these electrets of more than the limits specified above is to be investigated and corrective action taken in collaboration with the manufacturer. Note—Such corrective action may include invalidation of measurements already conducted with electrets of the type that exhibited voltage drift. 6.4 EIC Analysis QC—The Electret Voltage Reader 6.4.1 EIC Analysis—Annual Calibrations of Voltage Readers Calibration of the EIC analysis system includes calibration of both the voltage reader and the reference electrets used with every analysis session. The surface voltage reader is to be calibrated annually by the manufacturer (or a manufacturer-approved calibrator) and have a calibration certificate and a sticker visible indicating the date of the last calibration and the next calibration due date. The reader and electrets shall be from the same manufacturer. 6.4.2 EIC Analysis—Storage of Voltage Readers Readers are to be stored in an enclosure (i.e., a sealed protective case) that includes a humidity reduction device such as desiccant, which is changed at least every year and as necessary. 6.4.3 EIC Analysis—Checking Stability of Voltage Readers Prior to Analysis Session The EIC analyst is to check the reader’s stable operation using the reference electret(s) and record the reader’s response at least once during each analysis session, with results logged and available for review.