super(220)Rn and Its Progeny in Buildings in Sweden

Results are presented from two studies conducted in Sweden, which examined radon-220 levels in buildings. In the first study, most of the monitored buildings were located in areas with elevated natural thorium concentrations, while buildings were chosen at random in the second study. All super(220)Rn gas measurements were performed with the Falk More Nyblom multiple-time-analysis method, which is described. The progeny measurements were performed using alpha spectroscopy with two post-sampling counting periods. For the first study, the mean super(220)Rn progeny level in single-family houses was 0.9 Bq/m super(3), with lower levels found in multi-family buildings. Concentrations of super(222)Rn gas in basements were found to range 10 80 Bq/m super(3) typically. In the second study, the mean super(220)Rn gas concentration was 13 Bq/m super(3). Based on these data, the mean annual effective dose from inhalation of super(220)Rn gas in Sweden was calculated at less than 0.01 mSv.