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

The influence of Rn-222 exhalation from walls and air exchange (low ventilation rates nu < 0.3 h(-1)) upon its concentration in room air has been considered. It was found that the radon concentration reachs 84 Bqm(-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 alpha 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 Rn-222 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 Bqm(-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 (upsilon(d)(f)) of the ultrafine radionuclide Po-218 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(d)(f); of 4.6 mh(-1). The attachment coefficient beta of Po-218 was found to vary between 0.016 and 0.047 with a mean value 0.028 cm(3) h(-1). (C) 1998 Elsevier Science Limited. All rights reserved.