Behaviour of Radon Daughter Products in Indoor Air

Various parameters influencing the concentration of the radon daughter products in the atmosphere of dwellings are reviewed. The basic processes involved in attachment to the atmospheric aerosol, deposition (plateout) and recoil, which influence the activity balance of radon and radon daughters indoors, are reported. These processes depend on the physical properties of the free atoms and the activity size distributions of the atmospheric aerosol. In addition, the radon daughter concentrations relative to the radon concentration expressed by the so-called equilibrium factor F are influenced by room specific parameters such as radon emanation and ventilation. By means of a theoretical model the influence of the different parameters on the equilibrium factor F in houses is described, and the results are compared with experimental data.