Various means of face masks in the face of the outbreak of the Coronavirus, all taken in London's South Hole, Tuesday 5 May 2020.
Various means of face masks in the face of the outbreak of the Coronavirus, all taken in London’s South Hole, Tuesday 5 May 2020.

Researchers said Wednesday that face masks reduce the risk of the spread of large droplets that can transmit infection with Covid-19 when talking or coughing by up to 99.9%, according to a new laboratory experiment conducted on mannequins and on people.

They wrote in the journal “Royal Society Open Science” that a woman standing two meters away from a man coughing without a mask would be exposed to such drops by 10,000 times more than if he was wearing a mask.

“There is no doubt that face masks can significantly reduce the dispersion of potentially virus-laden droplets,” lead author Ignacio Maria Viola, an expert in applied fluid dynamics at the University of Edinburgh’s School of Engineering, told AFP.

He explained that the large respiratory droplets that come out in the form of droplets and act like projectiles before they fall to the ground by gravity are likely the main driver of transmission of the SARS-Cove-2 virus.

Smaller and finer droplets, which form so-called aerosols, which are suspended particles, can remain suspended in the air for long periods and pose a danger, especially indoors in poorly ventilated places, especially if they are crowded with people who do not wear a muzzle or misplace it under the nose.

“We constantly inhale a variety of drops, from the micro-scale to the millimeter scale, and some drops fall faster than others, depending on the temperature, humidity, and the speed of the airflow in particular,” the researcher said.

The study focused on particles over 170 microns in diameter, about two to four times the width of a human hair. Aerosol particles that tend to follow air currents are described as being smaller than 20 or 30 microns.

“In our study, we’re talking about a 99.9% decrease in the largest drops that we measure,” said Ignacio Maria Viola.

The World Health Organization recently updated its guidelines for masks to recommend that they be worn indoors in the presence of other people if ventilation is insufficient. Masks are mainly used to reduce the emission of virus-laden droplets from people coughing, sneezing, singing, talking, or simply breathing, but they can also help prevent inhalation of droplets by the people who put them in.

Universalizing the mask will reduce the number of deaths worldwide by 400,000 by April 1, according to the Institute for Health Metrics and Evaluation in Seattle, Washington.

“Sheet masks not only effectively prevent most large droplets measuring 20-30 microns or larger, but they can also prevent fine droplets and particles released with the exhalation, often referred to as an aerosol,” said the US Centers for Disease Control and Prevention. Aerial ”


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