Project Background
Charcoal Laboratories are required to perform calibration exposures annually to comply with industry protocols. Any change in charcoal or device type would also necessitate calibration exposures. Calibration exposures for charcoal devices are performed at three different values of relative humidity: nominally 25%, 50% and 75%. The temperature and radon concentration within the Radon Test Chamber are held as constant as practicable, nominally 70ºF and 25 pCi/L, for these exposures. The number of devices tested and the length of the exposures vary from client to client. Radon Laboratory personnel work with the client to determine the testing plan that best fits the client’s needs. These exposures follow the guidance provided in EERF Standard Operating Procedures for Rn-222 Measurement Using Charcoal Canisters (EPA 520/5-87-005) and Integrated Measurement of Indoor Air Using Activated Carbon (George, 1984).
Calibration Curves
Upon request the Radon Lab will calculate calibration curves based on the data from the calibration exposures. Prior methods have used graphs or look-up tables to choose a proper calibration factor for a particular sample. Bowser-Morner uses a curve fitting procedure to derive an equation for the calibration factor as a function of exposure duration and mass of water adsorbed. This makes it possible to perform the calculations using automated software to choose the best value for the calibration factor for each sample.