MS-QA_06-2019 rev5

ANSI/AARST MS-QA 2019 22 Radon Measurement Systems Quality Assurance EIC Analysis b) The pre-test and final surface voltage are to be measured using the same reader and preferably conducted by the same technician. c) The surface voltage is to be measured immediately after opening the device and exposing the electret surface. Informative advisory —If the EIC cannot be analyzed immediately, it should not be opened and should be stored in a low background radiation area until it can be read. d) The alignment of the electrets in the reader is to be consistent (e.g., serial numbers horizontal or otherwise consistent between readings). e) Surface voltage measurements for each electret are to be conducted at least three times. A measurement is not complete until at least three identical voltages are displayed, and this repeatable surface voltage is used as the test result. Informative advisory —If it is not possible to obtain three consecutive identical voltage readings, the manufacturer should be contacted for how to investigate a possible problem in the measurement system. 6.6 EIC Analysis—Required Calibration Factors Electrets of different sensitivities and chambers of different sizes can be used in combination to measure a range of radon concentrations over time periods from 2 days to 1 year. The formula required for converting voltage loss to radon concentration depends on the difference between the initial and final surface voltage, duration, calibration factors specific to the size of the ionization chamber and electret thickness, and, for some configurations, elevation (air pressure) corrections. Elevation correction factors account for alpha ionization path length inside the chamber and should be applied using algorithms and software that are available from the manufacturer. 6.6.1 Reported Test Results and Calibration Factors for Each EIC configuration The final reportable test results shall be derived from using the calibration factor that is established by the EIC manufacturer for specific EIC configurations. Each combination of chamber size and electret voltage, such as short- or long-term use electrets, requires that the analyst apply the correct calibration factor to the EIC configuration according to the manufacturer. 6.6.2 Reported Test Results and Calibration Factor Adjustments for Elevation and Gamma The final reportable test results shall include calibration factor adjustments established by the EIC manufacturer that account for elevation of the location tested and ambient gamma radiation. Note—The calibration relationship for EIC measurement systems includes subtraction of that proportion of voltage loss due to ionization caused by the ambient background gamma exposure rate (ion formation by gamma radiation). The vast majority of testing is done in locations where there is no information leading the technician to suspect that there is increased gamma exposure rate, and in these cases the state-wide average gamma exposure rates published by a relevant federal agency (Bogen and Smith 1981; Mauro and Briggs 2005; Oakley 1972) or supplied by the manufacturer can be used. 6.7 EIC Analysis—Verifying System Calibration and In-Control Operations Voltage reader calibration and field operation blanks , spikes and duplicates are required for maintaining in- control operations. Because spikes assess sources of error in the entire field/laboratory measurement system, continued calibration verification for EIC measurement systems is achieved using spikes with 3% of all tests conducted and with 6 per month and no fewer than 3 per year the maximum necessary.