Investigations of Rn sources in residential buildings

The results of investigations of mechanisms of diffusion and exhalation of Rn from building materials are presented and discussed. Parameters influencing the exhalation rate such as porosity and moisture contents of the materials as well as values influencing the equilibrium factor such as venting rate and aerosol concentration (smokers - non-smokers) are considered. The results on median Rn concentration (40 Bq/m3) in residential buildings show that in modern solid construction houses with an intact concrete slab and sufficient moisture insulation radon exhalation from the building materials is sufficient to explain the median of Rn concentration in living-rooms in areas with 'normal' contents in radionuclides of the soil. Comparative investigations showed that with broken concrete slabs Rn exhalation from the soil leads to much higher concentrations in the rooms. In the interpretation of the measured median concentrations in residential buildings the Rn exhalation from building materials is the major source of Rn concentrations. Only with high Rn concentration values in houses and in areas of increased Ra content in the soil exhalation from the soil are the prime Rn source. (orig./HP)