Common cloth and surgical masks allow for the build-up of aerosol droplets over time.
A recent study which was conducted by investigators from the University of Waterloo has found that better face masks and good ventilation can help to mitigate the spread COVID-19 while indoors.
Results from the study were published in the journal Physics of Fluids.
“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,” Serhiy Yarusevych, leader author on the study said. “However, there is a very serious difference in the effectiveness of different masks when it comes to controlling aerosols.”
For the study, the team of investigators conducted experiments which used a mannequin to simulate people seated and breathing in a large room.
Additionally, the team also quantified the impact that ventilation systems can have on the accumulation of aerosols.
Findings from the study demonstrated that the most commonly worn masks, such as cloth and surgical ones, only filter roughly 10% of exhaled aerosol droplets, mostly due to a lack of proper fitting. The other 90% of aerosols are redirected out of the top of the mask and into the ambient air.
Higher quality masks, such as N95 and KN95 masks were seen to filter more than 50% of exhaled aerosols.
The study also found that even moderate air filtration systems can be just as effective as the highest quality masks in reducing the risk of transmission.
“A lot of this may seem like common sense,” Yarusevych said. “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.”