Thoron, radon and air ions spatial distribution in indoor air

Spatial distribution of radioactive gasses thoron (Tn) and radon (Rn) in indoor air of 9 houses mostly during winter period of 2013 has been studied. According to properties of alpha decay of both elements, air ionization was also measured. Simultaneous continual measurements using three Rn/Tn and three air-ion active instruments deployed on to three different distances from the wall surface have shown various outcomes. It has turned out that Tn and air ions concentrations decrease with the distance increase, while Rn remained uniformly distributed. Exponential fittings function for Tn variation with distance was used for the diffusion length and constant as well as the exhalation rate determination. The obtained values were similar with experimental data reported in the literature. Concentrations of air ions were found to be in relation with Rn and obvious, but to a lesser extent, with Tn. •We studied spatial distribution of radioactive gasses thoron (Tn) and radon (Rn) and air ions in indoor air.•Exponential fittings function for Tn variation with distance was used for the diffusion constant, length and exhalation rate determination.•Concentrations of air ions were found to be in relation with Rn and with obvious, but to a lesser extent, with Tn.•The effective Tn diffusion length measured in different dwellings were in the range from 6 to 25 cm.