Indoor radon in three similar two-story houses with different ventilation systems

Abstract

Radon levels were monitored in three similar two-story apartment houses which were located side by side on a gravel esker in eastern Finland. The houses differed only in regard to their ventilation systems which included the following: natural ventilation, mechanical exhaust, and complete mechanical ventilation. The study started immediately when the houses were finished and was continued for two years. Radon concentrations were highest (60–430 Bq/m 3) in the beginning of the study period before the tenants moved in. During the following spring and fall, average radon levels of the houses decreased below 100 Bq/m 3. Radon concentrations varied within a wide range, from 20 to 230 Bq/m 3, in the apartments. Among the houses, the highest concentrations were found in the house equipped with mechanical exhaust ventilation and the lowest in the house with both a mechanical supply and exhaust system. One reason for the decreasing levels of radon after a one-year occupancy was that the tenants increased the ventilation of their apartments. In the house with complete mechanical ventilation, the stability of ventilation also contributed to the decrease of the indoor radon level.