The effect of filtration and exposure to electric fields on airborne radon progeny

The level of airborne short-lived decay products of /sup 222/Rn in indoor air is for a given radon feed determined by a series of removal processes like ventilation, filtration and plateout, both passive and electric field-induced. The paper describes a series of investigations, where various types of filters, mechanical and electrical, have been operated in rooms with radon levels ranging from about 100 Bq . m/sup -3/ to about 5000 Bq . m/sup -3/ and with aerosol concentrations up to 1 to 2 . 10/sup 11/ m/sup -3/. Measurements of individual radon progeny concentration and their unattached fractions show that by using filtration rates of up to 3 to 4 h/sup -1/ it is possible to lower the potential alpha energy concentration by a factor of 5 to 6, while the radiological doses to a certain part of the respiratory tract, according to the normally accepted dose models, for the same range of filtration rates will on the average only be reduced to about 50% of the value applicable to the air in the untreated state. The electrical properties, such as polarity, charged fraction and mobility of both attached and unattached radon progeny has also been studied, and some results of the effect on the radon progeny of exposing the air to an electric field are also reported