Ventilation effect on indoor radon–thoron levels in dwellings and correlation with soil exhalation rates

Abstract

This paper reports the measurements of indoor radon and thoron concentrations in selected Northern Indian dwellings (differing in ventilation rate). These were carried out using single entry pin hole based radon thoron dosimeters. In order to correlate the indoor levels with source term, the radon and thoron exhalation rates from soil samples collected from the same dwellings were also measured. Active measurement techniques with scintillation radon monitor and scintillation thoron monitor were used for exhalation measurements from soil sample. For thoron exhalation rate measurements, a small volume chamber was used. The indoor radon and thoron concentration in different rooms varied from 14 to 97 Bq/m3 and 23 to 189 Bq/m3, respectively. The radon mass exhalation and thoron mass emanation rates of soil samples varied from 28.2 to 91.2 mBq/kg/h and 3.42 to 12.1 mBq/kg/h, respectively. A weak correlation was found between indoor concentration and soil exhalation rates for these dwellings. Indoor radon concentrations from various rooms in the dwellings were lower than the limit (100 Bq/m3) recommended by WHO (2009).