Assessment and Mitigation of Infection Risk Caused by a Coughing Person

¹ Aalto University, Department of Mechanical Engineering, Espoo, Finland
² Nanjing Tech University, Department of HVAC, Nanjing, China

^* Corresponding author: simo.kilpelainen@aalto.fi

Abstract

The recent COVID-19 pandemic has increased public awareness of the importance of clean indoor air. Many studies have been conducted on how virus-like particles propagate in indoor environments, and how their spreading could be constrained. In this study, we assessed how the infection risk caused by a coughing person behaves in a meeting room. We analysed how well different protective measures (face masks, visors, air purifiers, partitions) can reduce the risk. The room had a floor area of 21 m² and was furnished with a conference table with seating for six people. The room was equipped with a mixing ventilation system providing fresh air at a rate of 36 l/s, or 1.7 l/s·m². The supply air temperature was 17°C and the room air temperature 23°C. The coughing person was realized by a cough/sneeze machine Ch3st developed by CH Technologies, USA. Paraffin oil was aerosolized with a BLAM nebulizer from the same company and released in bursts by the cough machine to emulate real coughs. A breathing thermal manikin (PT Teknik, Denmark) was used as the exposed person. Two TSI 3330 OPS optical particle sizers were used to assess the particle concentrations. There were 14 test cases in total. A case with no protective equipment was used as the reference. During each measurement, 21 coughs were released into the test room and the particle concentrations were monitored at one-second intervals from the exposed person’s breathing zone and from the infector’s workstation. Each cough reaching the exposed person produced a sharp peak in the particle concentration and the number of these peaks was used to assess the effectiveness of each protection measure. The distance between the opposite workstations was 120 cm. The results indicate that masks and visors on the infected person, and partitions, are effective protective measures against cough-based pathogens. Air purifiers and personal protection on the exposed person had little effect.