Study supports widespread use of better masks to curb COVID-19 indoors


Date:
August 19, 2021
Source:
University of Waterloo
Summary:
A new study is highlighting a need for widespread use of better
face masks and the importance of good ventilation to mitigate the
spread of COVID-19 indoors.



FULL STORY ==========================================================================
A new study is highlighting a need for widespread use of better face
masks and the importance of good ventilation to mitigate the spread of
COVID-19 indoors.


========================================================================== Engineering researchers at the University of Waterloo performed
experiments using a mannequin to simulate a seated person breathing
in a large room. The studies showed a significant buildup over time
of aerosol droplets -- exhaled droplets so tiny they remain suspended
and travel through the air -- despite the use of common cloth and blue
surgical 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 and the leader of the study. "However, there is a very serious difference in the effectiveness of different masks when it comes to controlling aerosols." Previous research has found that aerosols dispersed by infected people are
a source of transmission of the SARS-CoV-2 virus that causes COVID-19,
even outside the two-metre social distancing zone widely recommended by
public health officials.

The study showed that most common masks, primarily due to problems with
fit, filter about 10 per cent of exhaled aerosol droplets. The remaining aerosols are redirected, mostly out the top of the mask where it fits
over the nose, and escape into the ambient air unfiltered.

By contrast, higher-quality, more expensive N95 and KN95 masks filtered
more than 50 per cent of the exhaled aerosols that can accumulate indoors
and spread the COVID-19 virus when inhaled by other people.

Yarusevych, principal investigator in the Fluid Mechanics Research Lab,
said the much greater effectiveness of N95 and KN95 masks versus cloth
and surgical masks makes a compelling case they should be worn in indoor settings, such as schools and workplaces, as much as possible.

"A lot of this may seem like common sense," he 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." Experiments also quantified the
impact of ventilation systems, which circulate and replace air in rooms,
on the accumulation of aerosols. Even modest ventilation rates were found
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 the threat
posed by indoor aerosol accumulation as much as possible.

The study, Experimental investigation of indoor aerosol dispersion and accumulation in the context of COVID-19: Effects of masks and ventilation, appears in the journal Physics of Fluids.

Yarusevych collaborated with Sean Peterson, also a Waterloo professor
of mechanical and mechatronics engineering, and engineering PhD students
Yash Shah and John Kurelek.

========================================================================== Story Source: Materials provided by University_of_Waterloo. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Yash Shah, John W. Kurelek, Sean D. Peterson, Serhiy Yarusevych.

Experimental investigation of indoor aerosol dispersion and
accumulation in the context of COVID-19: Effects of masks
and ventilation. Physics of Fluids, 2021; 33 (7): 073315 DOI:
10.1063/5.0057100 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210819124528.htm

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