Estimation of indoor (220)Rn progeny concentrations with (220)Rn measurements

For estimating indoor thoron ((220)Rn) progeny concentrations with (220)Rn measurements, both theoretical studies and field measurements were carried out in this work. Based on the theoretical study, it was found that the exhalation rate of (220)Rn (E(Tn)) could be optimally assessed with the (220)Rn concentration measured at a point of 50 cm far from the source wall, and the equilibrium equivalent thoron concentration (EETC) could be further estimated with the E(Tn) and the area of wall surface as well as the room volume. Field measurements testified that the estimated EETCs were in general agreement with the directly measured results with an average ratio of 0.87 ± 0.12. The new method developed in this study is thought to be preferable for long-term and large-scale surveys of indoor EETC.