Strategies for reducing airborne disease transmission during breathing using a portable air cleaner in a classroom

In this work, computational fluid dynamics and a factorial study were conducted to analyze the air cleaning capabilities of a portable air cleaner (PAC) in a closed room with 10 thermal manikins and two air distribution system (ADS) speeds. The particles emitted by the breathing of the manikins (1,250 particles/manikin) were tracked for 50 min, and their trajectories were analyzed. Factorial analysis was performed to investigate the relevance of the variables studied and their interactions. The results showed that the PAC-ADS configuration was a major factor affecting the transference of particles. A total risk index was defined ( RItotal) to identify the total percentage of particles transferred between the occupants in each case. The best case had half the transference of particles compared with the worst case (2.03% vs. 3.98%, respectively). Moreover, locating the PAC with a downward flow direction near the emitter significantly reduced the transference of its particles. However, it increased the number of particles that this emitter received from others in the classroom. The factorial analysis showed that PAC speed contributed the most to the transference of particles (24%) and particles filtered by the PAC (25.8%). In comparison, PAC position had the highest impact on particles remaining in the breathable zone of the room (13.7%) and particles leaving the system through the ADS (23.3%). Overall, a configuration in which the PAC is at the center of the classroom with a downward flow was shown to be the most efficient for reducing the spread of airborne diseases.