MS-QA_06-2019 rev5

ANSI/AARST MS-QA 2019 21 Radon Measurement Systems Quality Assurance EIC Analysis QC procedures for the analysis are to include using at least one reference electret, and preferably two, which are used as a QC check for repeatability of the surface voltage reader. Note—Use of reference electrets are not a calibration of the reader, but rather a verification of the continued stability of the reader’s response. Informative advisory —It is recommended that the reader’s response to the reference electret(s) be verified at the end of any analysis session that results in radon concentration results that are greater than an action limit or otherwise unexpected for the location. Such good business practices protect the analyst in the event of questions about the data. 6.4.4 EIC Analysis—Control Limits for Voltage Reader Stability Informative advisory —If after three attempts, the voltage reading on reference electrets differs by more than the manufacturer’s limits for the difference from the electret’s specified value, the reader’s operation is suspect and the analyst should begin collaboration with the manufacturer to investigate and conduct corrective actions if needed. Results from that reader from that point and earlier until the last passing reference electret reading will be suspect and may be invalidated. 6.4.5 EIC Analysis—Annual Verification of Reference Electrets The continued applicability of reference electrets voltage is to be verified at least annually by the manufacturer. 6.5 EIC Analysis—Interferences 6.5.1 EIC—Analysis Environment (including both the reader and the EIC itself) The electret surface voltage and its measurement are affected by several critical factors, which are to be documented, kept within limits and consistent between voltage measurements. For the analysis environment: a) Electret surface voltage measurements used for reported radon measurements are to be made in a stable indoor environment in which the % RH is less than 60%. These conditions are to be measured and recorded at least once during each analysis session. Temperature and RH must be measured and documented, and the initial and final voltage readings must be conducted in RH environments not differing by more than 10%, or within tolerances established by the device manufacturer; b) The EIC detectors and the reader are to be equilibrated to the temperature in the analysis environment prior to measuring surface voltage. This may require waiting at least 60 minutes (or until a consistent, stable voltage is obtained, consistent with manufacturer recommendations) prior to measuring the surface voltage; and c) Both the pre-test and post-test surface voltage are to be measured in the same physical location to help ensure the repeatability of other factors that may affect surface voltage, including the background gamma exposure rate in the analysis environment. 6.5.2 EIC Analysis—Control of the Consistency of Equipment and Procedures The procedures used to conduct the readings are to be as reproducible as possible. a) Reader readiness checks are to be conducted prior to analyzing detectors including battery, dust checks and other pre-operational checks recommended by the manufacturer. Informative advisory —Compressed gas is to be used, if necessary, to blow dust off the electret or reader surface. A technician’s breath should never be used to remove dust.