Coronavirus: the classification of masks according to their effectiveness.

COVID – In your masks, brace yourself, wear? While indicators have been on the rise for several weeks for coronavirus contamination, particularly in Île-de-France, many municipalities have decided to reimpose the use of masks in public spaces, including in public areas. streets.

This time, there is no shortage, but on the contrary a certain variety: from the surgical mask to the tissue passing through the “Do it yourself“The French already accustomed to protecting themselves indoors can choose. But be careful, not just any piece of fabric will work: as a study by researchers at Duke University (USA) has just shown, a wrong choice could even increase the risk of transmitting the virus (see the video at the top of the article)!

Published in the magazine Scientific advances On August 7, the study compared the effectiveness of 14 different masks, among which is undoubtedly yours. N95 mask, surgical mask, cotton mask of different sizes and shapes, but also bandana and plush neckband, two accessories that are easy to put in front of the mouth. And the results cast a cold snap on these makeshift barriers.

The N95 champion all categories

The scientists maintained two criteria to measure the effectiveness of the masks: the number of postilions that cross the fabric barrier and their size, while a guinea pig utters a phrase. The sentence here is “Stay healthy folks”, or in French “Stay healthy”.

On these two criteria, the N95 respirator mask comes off unsurprisingly with the gold medal. Less than a thousandth part of the postilions manage to cross the barrier of the mask, during the whole time that the sentence is pronounced. The second place is undoubtedly for surgical masks that, properly placed, filter 99% of the projections. Then, way back, come washable masks, whether they’re store-bought or made at home.

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These range from a comfortable 95% filtration, for reusable masks with three layers of cotton-polypropylene-cotton, to 66% more fragile for knitted wool masks. Your reusable mask is likely to be found in this area, as are the DIY “barrier masks” recommended by AFNOR. These figures show, if necessary, that it is not enough to have a mask, but that your neighbor must also wear it so that the risk of transmission is minimal.

At the bottom of the ladder, the bad pupils are the famous scarf and the very useful fleece neck warmer. The first offers a filtration rate of 50%, with a particularly porous barrier at the beginning of the sentence, when you blow with special force against the cloth while speaking. So it offers limited protection, making it acceptable protection in the absence of anything else (especially when masks weren’t available), but should be replaced as soon as possible.

The choker, the disaster

The use of the neck strap is much less defensible, even when no other option is available. If the accessory seems naturally indicated, since it is sometimes put in the mouth to protect itself from the cold, it is not. Duke University measurements indicate that the garment does not decrease the number of postilions in the air … but increases.

How is it possible? Synthetic fiber, the researchers say, splits up the particles if they are not filtered. As a result, where cloth masks allow a small number of postillions of all sizes to pass through, the neckband blocks the “big ones” … leaving a third more than when speaking without protection.

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Fine particles and lots of it, this is really not good news, as we have learned from studies in recent months on the transmission of SARS-CoV-2 in the air. The smallest particles are in fact the lightest and therefore the ones that stay in the air the longest. However, if the question of aerosol transmission arises, then it is tested for contagion by droplets. Therefore, we will keep the wool collar warmer to protect your neck, which is not crazy after all.

See also in The HuffPost: Why Sports Wearing a Mask Is Not Recommended

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