Inter-comparison of three techniques for radon activity measurements

In this paper the results of an inter-comparison employing three distinct techniques for measuring indoor radon activities are discussed: (i) NRPB–SSI dosimeter, a diffusion chamber, CR-39 based, calibrated in a controlled radon chamber; (ii) a diffusion chamber, CR-39 based, calibrated via nuclear emulsion; (iii) canister with activated charcoal. Totally 39 dwellings of Poços de Caldas city (Minas Gerais State, Brazil), located in a high natural radioactivity region, have been monitored during a six months period.

Dosimeters (i) and (ii) were exposed continuously in all of 39 dwellings and dosimeter (iii) was exposed in 10 of them, randomly chosen. In this case the individual exposures lasted around 5 days and 4 equally time spaced exposures were made in each dwelling. Results produced by techniques (i) and (ii) show a great level of concordance. Individual results of technique (iii) for each residence show great fluctuations, but their mean results statistically agree with the other techniques. So our results indicate that active charcoal technique can be used to study average term radon variation (in few days), but its individual results cannot reflect long-term indoor radon activity.