The video shows why valve masks should not be used

The use of masks serves to prevent the spread of covid-19, but for months it has been known that not all protect in the same way and even some are harmful, such as valve masks.

The World Health Organization and the Centers for Disease Control and Prevention have expressed their opinion against the use of these valve masks. While they protect those who use them, they leave those nearby in danger.

Now, a new study published in the scientific journal Fluid physics visually shows how these masks put others at risk.

I study

Researchers from the National Institute of Standards and Technology (NIST) used various fluid dynamics techniques to show three different scenarios with air emitters. One person with a mask with a valve that exhales air, another person with an N95 mask without a valve and the third without a mask.

“These videos show how the valves allow air to escape from the mask without filtering it, which defeats the purpose of the mask,” says Matthew Staymates, engineer at NIST.

The experiments performed show that aerosols come out of the person’s mouth when he is not wearing a mask. The same is true, albeit in a more targeted way, when using valve masks.

Furthermore, the results of these experiments confirm that an N95 respirator without an exhalation valve is effective in blocking most of the droplets from penetrating through the mask material.

The recommendations

The authors point out that valve masks should only be used in some cases. In dusty places, where it is very difficult to breathe, as well as in hospital environments, where already infected patients are treated.

On the other hand, researchers recommend not using masks that do not fit the face, as they allow air to escape through the openings, which reduces their effectiveness.

“I don’t wear a mask to protect myself. I use it to protect my neighbor, because he could be asymptomatic and spread the virus without even knowing it, ”Staymates reiterates. “But if I’m wearing a mask with a valve, I’m not helping.”

Other studies

In a September report in the US journal Physics of Fluids, researchers from Florida Atlantic University used horizontal and vertical laser beams to observe how tiny droplets of distilled water and glycerin spread from a manikin’s head.

The visor initially blocks the passage of droplets, but “the ejected droplets can move around the visor relatively easily and spread over a large area,” the researchers said.

Meanwhile, with the valve mask, “a large number of drops pass through the valve without a filter. This makes it ineffective in stopping the spread of the virus if the person wearing the mask is infected ”.