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Radiation Protection Dosimetry 27:173-178 (1989)
© 1989 Oxford University Press
A Global Kinetic Model for the Adsorption of Radon Gas in Humid Air on Charcoal for US EPA Canisters
A global kinetic model for the adsorption of one gas in the presence of another can successfully be applied to describe the dependence of the calibration factor for EPA radon canisters upon water mass gain and canister exposure time. The model reveals that the dependences of George's and Watson's calibration factors upon time are artificial and are introduced by their definitions; not by physics. We recommend that the calibration factor be defined as CF=A/(E.CR.DF), where DF is a factor accounting for the decay of radon during the period from the end of the exposure to the start of counting. Decay of radon during the exposure period is not included in the decay factor. Also, we recommend that CF be plotted against canister water mass gain for DF=1, with exposure time as a parameter. For exposure times greater than three days, this yields a curve with intercept equal to 2.45±0.01 cpm.Bq-1.m3, and a slope equal to 0.0975±0.0014 cpm.Bq-1.m3.g-1.