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How long and effective does a mask protect you from an infected person who emits corona virus-laden particles: by implementing physics-based modeling

By Flora Bahrami, Till Batt, Seraina Schudel, Simon Annaheim, Weidong He, Jing Wang, Rene M Rossi, Thijs Defraeye

Posted 06 Jul 2022
medRxiv DOI: 10.1101/2022.07.05.22277221

SARS-CoV-2 spreads via droplets, aerosols, and smear infection. From the beginning of the COVID-19 pandemic, using a facemask in different locations was recommended to slow down the spread of the virus. To evaluate facemasks' performance, masks' filtration efficiency is tested for a range of particle sizes. Although such tests quantify the blockage of the mask for a range of particle sizes, the test does not quantify the cumulative amount of virus-laden particles inhaled or exhaled by its wearer. In this study, we quantify the accumulated viruses that the healthy person inhales as a function of time, activity level, type of mask, and room condition using a physics-based model. We considered different types of masks, such as surgical masks and filtering facepieces (FFPs), and different characteristics of public places such as office rooms, buses, trains, and airplanes. To do such quantification, we implemented a physics-based model of the mask. Our results confirm the importance of both people wearing a mask compared to when only one wears the mask. The protection time before the healthy wearer has an infection risk of 50% reduces by 80% if only one wears the facemask instead of both people. The protection time is further reduced if the infected person starts to cough or increases the activity level by 85% and 99%, respectively. Results show the leakage of the mask can considerably affect the performance of the mask. For the surgical mask, the apparent filtration efficiency reduces by 75% with such a leakage, which cannot provide sufficient protection despite the high filtration efficiency of the mask. The facemask model presented provides key input in order to evaluate the protection of masks for different conditions in public places. The physics-based model of the facemask is provided as an online application.

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