Cloth coverings only filter about 10% of exhaled aerosols, N95 masks more effective, study finds

Heavy duty N95 and KN95 masks are best at warding of COVID-19. Cloth face coverings filter only about 10 percent of exhaled aerosols, according to a new study.

“The results show that a standard surgical and three-ply cloth mask … filter at apparent efficiencies of only 12.4% and 9.8%, respectively,” according to the University of Waterloo study’s conclusion. But KN95 and N95 masks afford “substantially higher apparent filtration efficiencies (60% and 46% for R95 and KN95 masks, respectively) than the more commonly used cloth (10%) and surgical masks (12%), and therefore are still the recommended choice in mitigating airborne disease transmission indoors,” reads a summary of the study, published July 21.

The more expensive and higher-quality N95 and KN95 masks “filtered out more than 50 per cent of the exhaled aerosols that can accumulate indoors and spread the COVID-19 virus when inhaled by other people,” the study found. The study was published in the journal Physics of Fluids. It was conducted in a large, indoor and unventilated room.

One of the authors of the study said there are significant differences in the efficacy of various masks. “There is no question it is beneficial to wear any face covering, both for protection in close proximity and at a distance in a room,” said Serhiy Yarusevych, a professor of mechanical and mechatronics engineering. “However, there is a very serious difference in the effectiveness of different masks when it comes to controlling aerosols.”

Yarusevch said that the findings were in line with ‘common sense’. “A lot of this may seem like common sense,” said Yarusevych. “There is a reason, for instance, that medical practitioners wear N95 masks – they work much better. The novelty here is that we have provided solid numbers and rigorous analysis to support that assumption,” he added.



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Paul, 37, is from Scotland in the UK, but currently lives and works in Bangkok. Paul has worked in different industries such as telemarketing, retail, hospitality, farming, insurance, and teaching, where he works now. He teaches at an all-girls High School in Bangkok. “It’s a lot of work, but I love my job.” Paul has an active interest in politics. His reason for writing for FBA is to offer people the facts and allow them to make up their own minds. Whilst he believes opinion columns have their place, it is also important that people can have accurate news with no bias.

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