Experimental comparison of structural and active protective methods against breath- and cough-borne aerosols in a meeting room

In this experimental study, the focus is to address the challenges of cross-contamination due to the presence of an infected individual in a meeting room environment. A detailed analysis is performed to identify effective methods to reduce the spread of infectious aerosols generated due to breathing and coughing. Infectious aerosols are simulated using a Paraffin oil-based solution with a respiratory exhalation simulator integrated with a breathing/coughing machine and an atomizer. Filtration-based active strategies such as the room air purifier, personal air purifier, and facemasks (FFP2 and surgical) along their wearing patterns are examined and compared with structural measures such as face shields and partition walls. The impact of the infectors' location on the exposed person is also studied. Facemasks are the most effective protective measure for both examined respiratory activities and provide over 60 % protection. Other mitigating strategies behaved differently for breathing and coughing trials. In the well-mixed room, during breathing, the portable room air purifier designed for clean air delivery rates (CADR) 2.5 times the ventilation rate effectively reduced aerosol spread. A personal air purifier, with a flow rate of 0.02 times the ventilation rate, offered only partial protection to the exposed occupant. Structural partitions showed marginal effectiveness for breathing but were effective during coughing events. The infector's location has little impact on contaminant levels in a well-mixed meeting room, except for a slight increase when seated next to the exposed person. This study provides a valuable reference for using different mitigation strategies in indoor settings.