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. 218Po is nearly in secular equilibrium with its parent, 222Rn. Numerical experiments have shown that this is true within about 7%, even in cases of rapidly changing 222Rn concentrations and moderately high ventilation rates. For the experiments, conventional methods were used to measure the concentrations of airborne 218Po. Measurements in three high radon level houses yielded an average value of 4.9 m-1 for the surface to volume ratio. There were differences between houses, and these differences were plausible based on room architecture and furnishings.