According to the study, surgical masks stop more than 90% of the droplets produced by the word. The homemade masks in cotton are less effective.
The surgical masks stop more than 90% of the droplets emitted by the speech, according to a comparative study of 14 types of masks, which concludes that the bandanas and the cache-collar fleece are the least effective.
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For this experiment published by Science, Advances on 7 August, researchers from the american university of Duke, have made to talk about several of the participants hidden in a dark room to a laser beam, the scene being filmed (people kept saying : “Stay healthy, people”, “take care of yourself”). The number of spatters and droplets passing through the beam has been analyzed by computer.
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bandanas reduced the droplet 50%
not surprisingly, the masks to the hospital staff N95 (u.s. standard, equivalent to FFP2 in Europe) are the most effective, reducing the transmission of droplets of greater than 99.9%, in relation to a person speaking without a mask.
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Follow the medical masks three layers, which reduce more than 90%, and just behind the masks of polypropylene, and cotton/polypropylene. For the homemade masks in cotton, the reduction ranged between 70% and 90%, depending on the number of layers and pleating. The bandanas were to reduce the droplet of 50%.
The cache-collar in polar fleece, to avoid
The worst of the 14 masks tested was a cover-up collar in fleece, of the type of those used by the riders : this fabric has in fact increased the number of droplets, probably because the material dividing large droplets into smaller.
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“Covid-19”, the new coronavirus
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masks for professional medical N95 with a valve round were finally much worse than the N95 without valve and comparable to the masks of cotton, because the valve to help precisely to evacuate the exhaled air ; these masks are sold as “breathable”, but the authorities and experts advise against it because if they protect the wearer, they spread more easily contaminated air exhaled by a person.
