Effectiveness of plexiglass barriers in mitigating spread of aerosolized droplets in a cough

Abstract

Plexiglass barriers have been prevalently used in the workplace during the Covid-19 pandemic as protective measures against the airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) through interactions between potentially infected and uninfected individuals. Doubts have been raised about their effectiveness and concerns have even been expressed about the implications for room ventilation on their overuse. To aid public awareness of the role of such plexiglass barriers, we use flow visualization, aided by particle count measurements, to examine in a laboratory setting the effectiveness of typical workplace barriers in impeding the spread of aerosol-size airborne droplets. Such droplets are emitted in coughs and other respiratory exhalations and serve as modes of transmission for viruses. The visualizations and the supporting particle count measurements indicate that barriers do impede the forward momentum of the droplet-laden airflow jet that result from a cough, but portions of the expelled aerosols can spread around the barriers. Our study suggests that in comparison with the case in the absence of a barrier, a 2.5 ft or higher barrier can reduce the concentration levels of aerosols of size <10 μm on the side of the barrier away from the source by over 90% and those of size <3 μm by over 82%. However, an opening at the bottom of a barrier, for example, representing access for transactions between a worker and customers, can significantly reduce the effectiveness of the barrier. Finally, we illustrate how the aerosol dispersion in this case can be dramatically altered by ambient background airflows.