Radon exhalation and ultrafine fraction of radon progeny in closed room air

Abstract

The influence of 222Rn exhalation from walls and air exchange (low ventilation rates ν<0.3 h -1) upon its concentration in room air has been considered. It was found that the radon concentration reachs 84 Bq m -3 at exhalation and ventilation rates of 66 Bq hm -2 and 0.28 h -1, respectively. The radon concentration and the ultrafine fraction f p of potential α energy concentration as well as the equilibrium factor F of the short-lived radon progeny were also determined in three different completely closed rooms. An electroprecipitation method was applied for determining the 222Rn concentration while a single wire-screen technique was used for the determination of ultrafine radon progeny. During the measurements, the radon concentrations were varied between 33 and 134 with a mean value 89 Bq m -3. A mean ultrafine fraction ( f p ) of 0.16 was obtained at a mean aerosol particle concentration ( Z) of 1700 cm -3 and a mean equilibrium factor ( F) of 0.33. The obtained mean value of f p was found to be about five times higher than the value reported in the ICRP publication ( f p =0.03). The attachment rate ( X), the deposition rate ( q f ) and the deposition velocity ( v f d ) of the ultrafine radionuclide 218Po were calculated. A mean value of X was found to be 49 h -1 at a mean q f of 46 h -1 and a mean v f d of 4.6 m h -1. The attachment coefficient β of 218Po was found to vary between 0.016 and 0.047 with a mean value 0.028 cm 3 h -1.