COVID-19: Masks prevent 99.9% of large drops in an accident

Paris | Face masks reduce the risk of spreading large drops associated with COVID when talking or coughing by up to 99.9%, according to a new lab experiment with toys and humans, researchers said Wednesday.

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They reported in the Royal Society Open Science magazine that a woman standing two meters away from a man without a mask would be exposed to 10,000 times more drops than a person wearing a mask.

“Face masks will no doubt significantly reduce the scattering of virus-filled droplets,” lead author Ignacio Maria Viola, an expert in applied fluid dynamics at the School of Engineering, told AFP. University of Edinburgh.

Large postillion-like breath droplets that act as projectiles before being attracted to Earth by gravity – are believed to be the main driver for the transmission of SARS-CoV-2.

Small, fine droplets forming aerosols can be suspended in the air for long periods of time and indicate danger, especially in poorly ventilated areas without drafts, especially under crowded, uncovered, or poorly crowded areas.

“We constantly inhale the whole range of droplets from the micro scale to the millimeter scale”, and “some droplets fall faster than others depending on temperature, humidity and especially the current velocity,” the researcher said.

This study focused on cells with a diameter larger than 170 microns – two to four times the width of human hair.

Aerosol particles that follow air currents are usually described as smaller than 20 or 30 microns.

“In our study, for the largest points we measure, we are talking about a 99.9% reduction,” Ignacio Maria Viola emphasized.

The World Health Organization (WHO) has recently updated its guidelines for masks to recommend wearing them indoors in the presence of other people if ventilation is not adequate.

Masks are mainly used to reduce emissions of virus-laden droplets from those who cough, sneeze, sing, talk or inhale, but they also help prevent inhalation of droplets by the wearer.

The Institute for Health Metrics and Evaluation (IHME) in Seattle, Washington, says that wearing a universal mask will reduce the number of deaths worldwide by 400,000 by April 1.

“Sheet masks can not only effectively prevent very large droplets – 20-30 microns or more – but they can also inhibit fine droplets and particle inhalations called aerosols,” the US CDC said.