INEFFECTIVE TRANSPARENT VISORS AND VALVE MASKS

 Filenews 28 October 2020

Surgical and textile masks are more effective than plastic transparent visors and valve masks in preventing the spread in the air of coronavirus and the Covid-19 disease it causes, according to a new scientific study in the US.

As more and more countries around the world are aware of a new outbreak of the pandemic, masks are now seen as a "brake" against the spread of the virus, combined with distance keeping and hand washing. At the same time, the number of people who, for reasons of greater comfort, choose either protective masks or masks with an exhalation valve is increasing.

But the researchers, led by Assistant Professor Siddarda Verma of the College of Engineering at Atlantic University in Florida, who published the paper in the American journal Physics of Fluides, studied particle dispersion and how it varies depending on the type of mask, concluding that valve masks and masks may be more convenient for long-term use, but are less effective at preventing the spread of infections in the population.

In the case of visors it was confirmed that while they initially block droplets released by someone, then they with relative ease escape and spread in the air, spreading over a large area, depending on the conditions of the environment (e.g. if it is windy). On the other hand, a large number of droplets - possibly infected with the virus - penetrate the mask valve unfiltered, resulting in the wearer, if it is a carrier of the coronavirus, spreading it.

"As students and students now return to schools and universities, some wonder whether it will be better to use masks because they are more comfortable and easy to use for longer periods of time. But what if they're not as effective? In practice, inside an enclosed space, the droplets will accumulate over time, which can lead to infections," Verma said.

The researchers' laboratory experiments focused on smaller droplets, which can hover for longer and contain enough coronavirus particles to transmit Covid-19. The study concluded that in order to minimize the risks of the spread of SARS-CoV-2 virus in the community, it is preferable for people to wear cloth or surgical masks.

'The visors have large gaps at the bottom and sides, while valve masks limit the inflow of air during inhalation, but freely allow air to flow during exhalation. The inhaled air is filtered, but the exhaled one penetrates the mask unfiltered," Verma stressed.

However, according to the researchers, "even the best masks have particle leaks to some extent. It is therefore important to observe the physical distances while wearing the mask."

Source: RES- ICM