Comparative evaluation of air distribution systems for controlling the airborne infection risk in indoor environments

Abstract

Air distribution systems are essential for controlling indoor airborne cross-infection risks. However, there is no consensus on the most effective system. This study compares the effectiveness of common air distribution methods, including mixing ventilation (MV), displacement ventilation (DV), and stratum ventilation (SV), while considering specific influencing factors for each system. Factors such as inlet type for MV, airflow direction for SV, and relative body posture for DV were evaluated. Computational thermal manikins with actual breathing functions were simulated, and tracer gas (N2O) and particles of various sizes were used to simulate pathogen-laden droplet nuclei from an infected individual. The modified Wells-Riley model was employed to assess infection risk. Results indicate that no single air distribution system consistently outperforms others, with effectiveness depending on different conditions. Under the DV system, the highest infection risk (20.86 %) occurred when the infected person was seated, and the exposed person was standing, decreasing to 1.2 % when their positions were reversed. In SV system, the highest risk (17.58 %) was observed when the infected person with the same direction as the airflow, dropping to 1.01 % in the opposite direction. The study suggests using MV systems with adequate air volume when people's locations and relative positions are unclear.