Abstract

The present study summarizes the experimental data on the activity concentrations of²²²Rn gas , unattached  and attached  short-lived²²²Rn progeny ²¹⁸Po, ²¹⁴Pb and ²¹⁴Po in indoor air of Jeddah City, K.S.A. Jeddah  city  lies on the eastern bank of the red sea, South West the Kingdom of Saudi Arabia. The city is located between latitudes 21° 27^\ and 21° 30^\ N, longitudes 39° 9^\ and 31° 12^\ E. By means of theoretical model calculation, the unattached fraction (f_P) of ²¹⁸Po, ²¹⁴Pb of potential alpha energy of ²²²Rn progeny, the equilibrium factor (F), the attachment rate (X) to aerosol particles in the room air, the attachment coefficient (B) and the deposition rates of unattached (q^f) and attached (q^a) of ²²²Rn progeny on walls and other surfaces were calculated. The measurements were performed at different days in three different rooms of same size at low and moderate ventilation rates. An electrostatic precipitation method and a single wire-screen diffusion battery technique were both employed for the determination of ²²²Rn gas concentration and its unattached progeny, respectively. At low ventilation rate (υ ≤ 0.4 h^–1) a mean unattached fraction (f_P) of 0.096±0.01 was obtained at a mean aerosol particle concentration (Z) of 2.6×10³ cm^–3 and at a mean equilibrium factor (F) of 0.34 ± 0.02. The mean deposition rates of unattached (q^f) and attached (q^a) ²²²Rn progeny were found to be 94±13 h^–1 and 0.12±0.05 h^–1, respectively. The values of the recoil factor were neglected. At moderate ventilation rate of υ = 0.5 h^–1 a mean value of f_P = 0.059±0.006 was obtained at a mean aerosol concentration Z = 29×10³ cm^–3 and at a mean F = 0.24±0.014. In this case the mean value of the recoil factor was found to be 0.54±0.18.      

Key words: Unattached fraction, aerosol attached, theoretical model calculation, radon progeny.