Reduction of radon progeny concentration in ordinary room due to a mixing fan

Three experiments were carried out at the Indoor Air Quality Research House (IAQRH) at Lawrence Berkeley Laboratory, University of California, to study the effect on the radon progeny of operating a mixing fan. At the beginning of every experiment, about 15 kBq · m^-3 of radon was injected into a 36 m³ ordinary room. Measurements were conducted with three different aerosol particle concentrations of about 10², 10⁴ and 10⁵ per cm³. Real-time measurements of radon and progeny concentrations, particles and environmental parameters, were made throughout the experiments. Measurements of plated out activity on the surfaces of internal walls of the room and fan blades were measured directly by filter papers and CR-39 nuclear track detectors placed on the surfaces. The ratio of plated out activity to the total progeny activity in the room varied from 17% to 84%, in inverse relation to the particle concentrations. More than 99% of the plateout activity was found on walls and less than 1% on the fan blades.