The influence of radon and thoron exhalation from the walls and the airexchange upon the Rn ('**Rn)-and Tn(Z20Rn)-concentration indoors has been studied. On the basis of a simple room model the degree of equilibrium between radon, thoron and their decay products, free and attached fraction, has been calculated. These calculations were performed under consideration of: (1) the measured natural radioactive indoor and outdoor aerosol size distribution, (2) the known attachment rate of the uncombined decay products, (3) the experimentally evaluated recoil factor, and (4) of an estimated deposition rate on the wall surface.

Radon-222 concentrations have been measured in 12 homes typical of a small town in the southwestern United States. Nine of the houses, in which both summer and winter data are available, have an annual mean of 63 +/- 18 Bq m-3 (1.7 +/- 0.5 pCi L-1) and a range of 41 to 96 Bq m-3 (1.1 to 2.6 pCi L-1). These results were obtained with passive Rn dosimeters using polycarbonate nuclear track detector foils. The overall results fall slightly above the middle of the range of values obtained in other studies in the United States. Winter levels clearly exceed summer by a factor of from two to three. This result is attributed primarily to wide use of evaporative air conditioners for daytime cooling in the summer together with the fact that doors and windows are left open frequently during evening and nighttime hours. Both practices enhance the exchange of outdoor air with indoor air contributing to a decrease in the indoor Rn levels during the summer season. Room-to-room differences were evident during the winter season only. Bedrooms and bathrooms were generally higher in Rn than kitchens and living rooms but by only about 25%. The two adobe houses in the group showed higher Rn concentrations during the winter season than did those of frame-stucco, concrete, or cinder block construction. Dose equivalent calculations yielded a mean figure of 0.29 WLM y-1 for typical occupancy patterns in these New Mexico houses.

No abstract

No abstract

No abstract