Experimental evaluation of the airborne infection probability in ventilated office room at different supply airflow rates

Abstract

The impact of the supplied airflow rate on the distribution and exposure of exhaled airborne pathogens in a room with mixing ventilation was studied. Experiments were conducted in a field laboratory at three supply airflow rates: 20, 40, 60 L/s. Two breathing thermal manikins were used to resemble infected and susceptible occupants. Nitrous oxide (N2O) was dosed into the air exhaled by the infected manikin to simulate the emission of infectious aerosols. N2O concentration was measured in the air inhaled by the susceptible manikin. The measured data were used to calculate infection probability by modified Wells-Riley model. The highest infection probability of 4.3-5.1%, obtained in the case of 20 L/s, decreased with increasing the supply airflow rate. The decrease slowed with the increase of the supply flow. The calculated infection probability based on the tracer gas concentration in the inhaled air of the exposed manikin was in all studied cases higher than the infection probability obtained in the occupied zone and the exhaust. The infection probability based on the tracer gas concentration in the inhaled air of the exposed manikin was up to 65% higher than the infection probability calculated by the Wells-Riley method, which assumes complete room air mixing.