Estimation of ventilation rates in dwellings

Several methods using gaseous tracers such as nitrous oxide, or the radioactive tracer 85Kr have been used for estimating ventilation rates in rooms. This paper presents a method to evaluate the ventilation rate using radon daughter aerosol normally present in a room as a tracer. By using solid-state nuclear track detectors (SSNTD), radon and its progeny levels are determined. For a steady-state level of radon and its daughter concentrations, the ratio of working level (WL) to radon is estimated. This ratio is related to the pseudo -ventilation rate which is the sum of actual ventilation rate and plate-out rate as follows: WL= f a ×10 -5(2.8+14 f b · f c ) C Rn The actual ventilation rate is obtained by subtracting the plate -out rates of attached and unattached fractions of radon daughters from the pseudo-ventilation rate. The results of the measurements carried out in 18 different types of houses in Bombay are presented.