Thoron versus Radon: Comparison of Measured Progeny Aerosol Size Distributions

A review of the literature showed that measurements of the comparative size of radon and thoron progeny have yielded mixed results. On the other hand, a theoretical analysis showed that differences might be expected in certain circumstances. Therefore, we reviewed our archived and recent measurements of radon progeny particle size to see if information on thoron progeny particle size can be extracted. The data reviewed include tests done in our 20 m 3 radon test chamber and in three single-family houses in New Jersey. To determine if there were significant differences in the radon and thoron progeny particle size, a Monte Carlo error analysis was carried out on these test data. From these studies we conclude that the difference between radon and thoron progeny particle size is too small to be measured.