• Live.Last minute on the coronavirus

  • Phase 3 Results Pfizer Claims Its Covid-19 Vaccine "90% Effective"

If in recent months you have gotten on a plane with a mask with a valve, you have probably been asked to change it for another that did not have it incorporated.

The reason is the same for which it has been banned in communities such as Madrid and Galicia and its use is only recommended to some health professionals.

Masks with an exhalation valve protect those who wear them but not the rest of the population

since they let the droplets that are produced when breathing and speaking escape more easily, so they are not effective in preventing the spread of the virus.

This is confirmed by a study published this Tuesday in the specialized journal

Physics of Fluids

.

The results are accompanied by several videos produced by the National Institute of Standards and Technology (NIST) that show the difference between wearing an N95 mask (equivalent to the European FFP2) with or without an exhalation valve.

"When you compare the images from the two videos, the difference is striking.

They show how the valves allow air to escape from the mask without being filtered, thus defeating the objective of wearing a mask,

" says study author, engineer Matthew Staymates. .

In countries like Spain and Greece, the use of a mask is mandatory in any public space, whether indoors or outdoors.

In others it is not compulsory in the street but it is in closed places, in some in a generalized way and in others in certain places, such as means of transport or health centers.

In the US, the Centers for Disease Control and Prevention (CDC) recommend wearing it on public places to slow the spread of the virus.

Valve masks, however, do not serve that purpose.

"The valve is basically a little flap that opens when you exhale, letting the air out without seeping through the mask material," says Staymates, who compared different types of masks and materials in a makeshift lab.

To show how the exhalation valve works, he devised an artificial exhalation system that mimics the exhalation flow pattern of a person and a mist generator inside the head of a mannequin that produced droplets similar to those we produce when we breathe and speak. .

The most effective masks

"Our current knowledge is that Covid-19 is transmitted in part through respiratory droplets, so valve N95s are not good for pandemic control," says the American engineer.

In contrast,

valveless N95 masks blocked most droplets.

"

The valve of the masks helps not to accumulate humidity and they can be more comfortable but do not protect more

than equivalent masks that do not have a valve", points out Jesús Miguel Santamaría, director of the Institute of Biodiversity and Environment of the University of Navarra .

As this professor in Analytical Chemistry points out in a telephone conversation, unrelated to the US study, the valves are usually on the front or side of the mask so droplets are projected when breathing and speaking and can facilitate infection. people if the user of the mask is infected: "It seems appropriate that its use is not allowed indoors," he says.

However, he emphasizes that

with all masks

, whether surgical, FPP1, FPP2 (N95) or hygienic

, part of the exhaled air escapes to the outside

, usually through the sides: "

All of them release particles that may contain the virus,

that's why it is important to put them on correctly and that they fit very well to the face, avoiding space on the sides ", he recommends.

Although we have become accustomed to wearing them and their use is mandatory in our country, the chemist warns of the misuse that is being done in Spain and the low quality of some of the masks that are sold: "Personally, I would prefer to go by plane with a person that takes a mask with a valve to another that wears a mask of poor quality, "he says.

After testing hundreds of models and brands in his laboratory at the University of Navarra, he recommends the use of good quality surgical masks in addition to FFP2: "

If they fit the face well and are of quality, surgical

masks

protect almost as much as a FFP2

and in both directions, that is, they protect you and protect others if you are infected. "

The researcher

advises against the use of hygienic cloth masks

: "I see many errors, even in politicians, who wear them by design, but most cloth masks have very little filtering capacity and do not protect you. Of course, a doctor should never wear them, "he says.

SELFISH MASKS

Fernando Simón, director of the Center for Coordination of Health Alerts and Emergencies of the Ministry of Health, has referred to the FFP2 masks, both with valve and without valve, as "selfish masks": "The problem with the valve is that the air that exhales the person who wears it concentrates it in a specific point and that can cause that at some point, someone who is exposed to the air that comes out of the valve can become infected. But if a person is sure that they are not infected and are vulnerable , you can consider the use of FFP2, better without a valve, "he said during one of his press conferences.

"If there is no other option, the use of these masks may be useful but it is not ideal from a population point of view, because what interests us is that anyone who could be infected does not transmit the virus, and that is why we have to look for altruistic masks, the one that prevents you from infecting others. "

According to the criteria of The Trust Project

Know more

  • Science and Health

  • Coronavirus

  • Covid 19

Research Antibodies against Covid protect for at least seven months

Pandemic The mathematics of Covid: what real probability do I have of getting sick?

P & RHigiene, 'micro hugs' and bubble meetings: how to avoid Covid infections among family members

See links of interest

  • News

  • Translator

  • Programming

  • Films

  • Topics

  • 2021 business calendar

  • Girona - Las Palmas