We’ve all learned by now that wearing a mask is one way to help stop the spread of COVID-19 around the world. But the message should be expanded a bit more. It is not useful just to wear the mask: you have to wear it well adjusted to the face to be effective.
Properly fitting the mask can protect users from approximately 96% of the aerosol particles believed to spread the coronavirus, as long as both people are, according to a new study from the US Centers for Disease Control and Prevention. wear a mask . If one does not use a mask, the user who does wear it will be protected from 64.5 to 83% of potentially virus-carrying particles.
Masks are really effective
“The bottom line is this: Masks work and work best when they fit well and are worn correctly,” says CDC Director Rochelle Walensky emphatically.
That message is becoming increasingly important as more transmissible coronavirus variants, including those first detected in South Africa and the United Kingdom, are beginning to spread more widely across countries around the globe.
Many studies have already shown that masks reduce the amount of saliva particles that can jump towards other people when someone breathes, speaks, coughs or sneezes. Still, photos and videos show that air and droplets often escape from the top, sides and bottom of masks that do not cover us well.
Several recent studies have shown that certain fairly simple measures to improve the fit of the mask to the face also reduce aerosol emissions, such as the use of ear protectors, mask adjusters, or placing a cloth mask over a surgical mask .
The effect of tight fitting mask
In one study, researchers placed two mannequins facing each other almost 2 meters apart. A mannequin served as the source, “exhaling” through an aerosol tube particles of salt water of a size that could carry the coronavirus. The other mannequin was the receiver. The experts measured how many drops of saline solution reached the mouthpiece of the receiving manikin that represented his nose and throat. In some experiments, they put surgical masks on just one of the manikins. In others, both wore masks. They tried two scenarios to make the mask fit better: knotting the ear muffs close to the mask and tucking in the ends to eliminate side gaps; and wear a cloth mask over the surgical one.
In each of the tests, the results were compared with the possibility of not wearing a mask.
When the recipient wore a mask that did not fit well, that was too large or baggy , the number of drops that reached their throat was reduced by only 7.5%. When the source was the one wearing the mask, the receptor’s exposure was reduced by 41.3%. And when both manikins wore masks, the particulate exposure was 84.3% lower than without a mask. And when both mannequins wore the masks well knotted and tucked in, the protection was even stronger: exposure was reduced by 95.9%.
Wearing a cloth mask over the surgical procedure further improved the fit. When only the receiving phantom wore a double mask, 83% of the particles were protected. And when both mannequins wore double masks, 96.4% of the particles were blocked.
These data show that “it is the fit of the mask that really matters, and there are many different ways to improve it,” says David Rothamer, a mechanical engineer at the University of Wisconsin-Madison School of Engineering, co-author of one of the papers. .
Why does the double mask work better?
The medical mask material is electrostatically charged, which can repel microbes as well as filter out particles. The cloth mask helps reduce the gaps around the sides and top of the surgical mask. According to experts, the order of the double mask does not have to be important : we can wear the cloth underneath and the surgical one on top.
Referencia: J.T. Brooks et al. Maximizing fit for cloth and medical procedure masks to improve performance and reduce SARS-CoV-2 transmission and exposure, 2021. Morbidity and Mortality Weekly Report. February 10, 2021. doi: 10.15585/mmwr.mm7007e1
D.A. Rothamer et al. Strategies to minimize SARS-CoV-2 transmission in classroom settings: Combined impacts of ventilation and mask effective filtration efficiency. medRxiv.org. January 4, 2021. doi: 10.1101/2020.12.31.20249101
M. Gandhi and L.C. Marr. Uniting infectious disease and physical science principles on the importance of face masks for COVID-19. Med. Vol. 2, January 15, 2021, p. 29. doi: 10.1016/j.medj.2020.12.008
