Higher quality, more expensive masks are significantly better at helping to stop the spread of COVID-19 indoors, a new study has highlighted.
A team of engineer researchers from the University of Waterloo in Canada used a mannequin to simulate a person sitting down and breathing in a large room.
The experiment showed that, despite the use of common cloth and blue surgical masks, there was still a significant build-up over time of aerosol droplets, which are the tiny droplets that are exhaled and remain airborne and can travel in the air.
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The findings also show that the common cloth masks only filter about 10 per cent of these exhaled droplets, largely due to the masks not fitting correctly. The rest of these aerosols escape in the most part out of the top of the mask, around the nose.
In comparison, the better quality N95 and KN95 respiratory masks filtered more than 50 per cent of the exhaled aerosols.
Study lead Serhiy Yarusevych, a professor of mechanical and mechatronics engineering, said: “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. However, there is a very serious difference in the effectiveness of different masks when it comes to controlling aerosols.
“A lot of this may seem like common sense. 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.”
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He said the study showed that these more effective masks should be worn in indoor settings, including schools and workplaces, as much as possible.
The effect of ventilation on the accumulation of aerosols was also explored, with the team finding that even small ventilation rates can work just as well as the better-quality masks in terms of reducing transmission of COVID-19.
They concluded that the higher-quality masks should be combined with ventilation to reduce the risk of transmission.
The study has been published in the journal, Physics of Fluids.
