Heavy duty N95 and KN95 masks are best at warding of COVID-19, while commonly worn surgical and 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 masks … 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.
Pricier, high-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 an 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.”
He explained that the study’s findings tracked with “common sense” and prevailing health-care practices.
“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.
