Rn-222, Rn-220 and their progeny concentrations in offices in Hong Kong

An active sampling system using charcoal canisters and an HPGe gamma-spectr ometer was employed to survey Rn-222 and Rn-220 concentrations in 65 office s in Kong Kong, and a traditional method was used to record simultaneously the potential alpha-energy concentrations (PAEC) of Rn-222 and Rn-220 proge ny at the same sites. The mean values of gas concentration, PAEC and equili brium factor for Rn-222 were 48 +/- 32 Bq m(-3), 5.2 +/- 5.1 mWL and 0.38 /- 0.13, respectively, and the corresponding values for Rn-220 were 14 +/- 7 Bq m(-3) 2.7 +/- 2.1 mWL and 0.050 +/- 0.016. These values were in genera l higher than those in dwellings in Hong Kong, which was due to the poorer fresh air exchange in offices. Factors affecting the concentrations of Rn-2 22, Rn-220 and their progeny were also studied. The type of air conditioner s and the indoor and outdoor temperature difference show some effects on Rn -222, Rn-220 and progeny concentrations, while rainfall and relative humidi ty affect only the progeny concentrations. (C) 2000 Elsevier Science Ltd. A ll rights reserved.