Airborne Transmission of Virus-Laden Aerosols inside a Music Classroom: Effects of Portable Purifiers and Aerosol Injection Rates

Narayanan, S. R.; Yang, S.

The ongoing COVID-19 pandemic has shifted attention to the airborne transmission of small exhaled droplet nuclei within indoor environments such as classrooms. The spread of aerosols through singing and musical instruments in music performances has necessitated the need for utilizing precautionary methods such as masks and portable purifiers. This study investigates the effects of placing portable air purifiers at different locations inside a classroom, as well as the effects of different aerosol injection rates (e.g., with and without masks, different musical instruments etc.). The time varying deposition of aerosols on the walls and the airborne aerosol concentration are analyzed in this study. It was found that proper placement of purifiers could offer a significant advantage in reducing airborne aerosol numbers (offering orders of magnitude higher aerosol removal when compared to having no purifiers, where the removal is sometimes nearly zero), while improper placement of the purifiers could worsen the situation. It was concluded that in general, the purifier should be placed as close to the injector as possible in order to yield a benefit, and also away from the people to be protected. Moreover, using purifiers could help in achieving ventilation rates close to the prescribed values by WHO, while also achieving aerosol removal times within the CDC recommended guidelines. This could help in deciding effective break periods between classroom sessions, which was found to be around 25 minutes through this study. The injection rate was found to have an almost linear correlation with the average airborne aerosol suspension rate and aerosol surface deposition rate, which could be used to predict the trends for scenarios with other injection rates.