Influence of office furniture on exposure risk to respiratory infection under mixing and displacement air distribution systems

The furniture layout between two people complicates the interaction between indoor airflow, human thermal plume, and exhalation flow in the breathing microenvironment. It thus increases the uncertainty of exposure risk assessment. This study aims to investigate the effects of office furniture under two different air distribution systems on the transmission of respiratory contaminants and airborne cross-infection risk between two people using a computational fluid dynamics method. Two thermal manikins models with realistic breathing functions were simulated, sitting face to face at two separation distances between their mouths in a single-office room served by a mixing ventilation system (MV) and displacement ventilation system (DV). Tracer gas (N2O) was used to simulate small droplet nuclei pathogen-laden exhaled by the infected person, and the exposure risk was assessed using the intake fraction (IF) index. The results show that placing a desk in the microenvironment between two occupants increased the exposure risk by about 50% under DV conditions and 22% under MV conditions compared with the cases without a desk. The exposure risk was reduced remarkably by increasing the separating distance. The results show that the furniture layout significantly affects the airborne transmission risk and cross-infection, and this effect varies with the ventilation conditions and separation distances between the occupants.