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Credit: University of Waterloo
Study supports widespread use of better masks for braking COVID-19[feminine à l’intérieur.
Une nouvelle étude met en évidence la nécessité d’une utilisation généralisée de meilleurs masques faciaux et l’importance d’une bonne ventilation pour atténuer la propagation du COVID-19 à l’intérieur.
Les chercheurs en génie de la Université de Waterloo ont réalisé des expériences à l’aide d’un mannequin pour simuler une personne assise respirant dans une grande pièce. Les études ont montré une accumulation importante au fil du temps de gouttelettes d’aérosol – des gouttelettes exhalées si minuscules qu’elles restent en suspension et voyagent dans l’air – malgré l’utilisation d’un tissu commun et de masques chirurgicaux bleus.
“Il ne fait aucun doute qu’il est bénéfique de porter un couvre-visage, à la fois pour se protéger à proximité et à distance dans une pièce”, a déclaré Serhiy Yarusevych, professeur d’ingénierie mécanique et mécatronique et responsable de l’étude. “Cependant, il existe une différence très sérieuse dans l’efficacité des différents masques lorsqu’il s’agit de contrôler les aérosols.”
A video made by researchers at Waterloo Engineering shows how much aerosol-laden exhalation flow escapes unfiltered when you are not wearing (left to right) any mask, KN95 mask, and surgical mask.
Previous research has shown that aerosols dispersed by infected people are a source of transmission of SARS-CoV-2 virus that causes COVID-19, even outside the two-meter social distancing zone widely recommended by public health officials.
The study showed that the most common masks, mainly due to fit issues, filter about 10 percent of exhaled aerosol droplets. The remaining aerosols are redirected, mainly to the top of the mask where it fits over the nose, and escape into the ambient air without a filter.
In contrast, the better and more expensive N95 and KN95 masks filtered over 50% of exhaled aerosols that can build up inside and spread the COVID-19 virus when inhaled by other people.
Yarusevych, principal investigator of the Fluid Mechanics Research Lab, said that the much greater effectiveness of N95 and KN95 masks compared to fabric and surgical masks argues for their wearing as much as possible in indoor environments, such as schools. and workplaces.
“Much of this may sound like common sense,” he said. “There’s a reason, for example, why doctors wear N95 masks – they work much better. The novelty here is that we have provided solid numbers and rigorous analysis to support this hypothesis. “
Experiments have also quantified the impact of ventilation systems, which circulate and replace air in rooms, on the accumulation of aerosols. Even modest ventilation rates have been shown to be as effective as the best masks in reducing the risk of transmission.
Ideally, Yarusevych said, the evidence shows that high-quality masks and proper ventilation should be used in combination to mitigate as much as possible the threat posed by aerosol buildup inside.
Reference: “Experimental Investigation of Indoor Aerosol Dispersion and Accumulation in the Context of COVID-19: Effects of Masks and Ventilation” by Yash Shah, John W. Kurelek, Sean D. Peterson and Serhiy Yarusevych, July 21, 2021, Fluid physics.
DOI: 10.1063 / 5.0057100
Yarusevych collaborated with Sean Peterson, also professor of mechanical and mechatronic engineering at Waterloo, and doctoral engineering students Yash Shah and John Kurelek.
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