Determination of the Surface to Volume Ratio in Homes from Measurements of Radon and its Progeny

An activity balance method is proposed for measuring the ratio of surface area to volume in houses. The method is based on the assumption that, after accounting for surface as well as airborne activity, 218 Po is nearly in secular equilibrium with its parent, 222 Rn. Numerical experiments have shown that this is true within about 7%, even in cases of rapidly changing 222 Rn concentrations and moderately high ventilation rates. For the experiments, conventional methods were used to measure the concentrations of airborne 218 Po and 222 Rn, and a surrogate surface method was used to measure the surface concentration of 218 Po