Face Coverings, Aerosol Dispersion and Mitigation of Virus Transmission Risk
Ignazio Maria Viola, Brian Peterson, Gabriele Pisetta, Geethanjali Pavar, Hibbah Akhtar, Filippo Menoloascina, Enzo Mangano, Katherine E. Dunn, Roman Gabl, Alex Nila, Emanuela Molinari, Cathal Cummins, Gerard Thompson, Tsz-Yan Milly Lo, Fiona C. Denison, Paul Digard, Omair Malik, Mark J. G. Dunn, Catherine M. McDougall, Felicity V. Mehendale
Abstract
The SARS-CoV-2 virus is primarily transmitted through virus-laden fluid particles ejected from the mouth of infected people. Face covers can mitigate the risk of virus transmission but their outward effectiveness is not fully ascertained. Objective: by using a background oriented schlieren technique, we aim to investigate the air flow ejected by a person while quietly and heavily breathing, while coughing, and with different face covers. Results: we found that all face covers without an outlet valve reduce the front flow through by at least 63% and perhaps as high as 86% if the unfiltered cough jet distance was resolved to the anticipated maximum distance of 2-3 m. However, surgical and handmade masks, and face shields, generate significant leakage jets that may present major hazards. Conclusions: the effectiveness of the masks should mostly be considered based on the generation of secondary jets rather than on the ability to mitigate the front throughflow.