The size distribution of the unattached short-lived radon decay products

The size distributions of the short-lived radon decay products Po-218, Pb-214 and Bi-214 were measured with a diffusion battery technique in 4 living rooms and at 2 working places. The maximum diameters of the radioactive clusters are smaller than 5 nm and the median diameters range between 0.5 and 3 nm. There are some indications of four different, discrete modes depending on the atmospheric conditions, the residence time and the chemical behaviour of the different nuclides.