Abstract :
This study summarizes the experimental data on the activity concentrations of radon gas (C0i), unattached (C1if, C2if) and attached (C1ia, C2ia, C3ia) 222Rn progeny 218Po, 214Pb and 214Po in indoor air. By means of a theoretical model calculation, the unattached fraction (fp) of potential α-particle energy of Rn progeny, the equilibrium factor (F), the attachment rate (X) to aerosol particles in the room air, the attachment coefficient (β) and the deposition rates of unattached (qf) and attached (qa) Rn progeny on walls and other surfaces were calculated. The measurements were performed in three different rooms with different aerosol sources and different ventilation rates. An electrostatic precipitation method and a single-screen technique were used for the determination of the concentrations of Rn gas and its progeny, respectively. At low ventilation rate for exchanges per hour in a given room size (ν< 0.3 h−1) and without aerosol sources, a mean unattached fraction (fp) of 0.06 ± 0.005 was obtained at a mean aerosol particle concentration (Z) of 2.9 × 103 cm−3 and at a mean equilibrium factor (F) of 0.34 ± 0.011. The mean deposition rates of unattached (qf) and attached (qa) Rn progeny were found to be 170 ± 23 h−1 and 0.225 ± 0.092 h−1, respectively. The values of the recoil factor were neglected. At moderate values of ν > 0.4 h−1 and without aerosol sources, a value of fp = 0.042 ± 0.018 was obtained at Z = 37 (±4) × 103 cm−3 and at a mean F = 0.29 ± 0.008. In this case the mean value of the recoil factor was found to be 0.63 ± 0.21. At low ventilation rate (ν < 0.3 h−1) and with additional aerosol sources (cigarette smoke or candlelight), the aerosol particle concentrations ranged up to 260 × 103 cm−3 and the attachment rates increased up to 3600 h−1. The fp values sometimes decreased to 0.004 and the F values increased to 0.52. The mean values of the recoil factor (r) were found to be 047 ± 0.05 and 0.28 ± 0.02 with burning candle and cigarette smoke, respectively.
