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A new study claimed that wearing a used mask may be less effective in protecting against the Corona virus than not wearing it at all.
The researchers looked at three-layer surgical masks, which are very common among healthcare professionals.
And they found that when new, these masks can filter nearly three-quarters of the fine particles in the air that are primarily responsible for infection.
But when used more than once, it filters out only a quarter of the tiny droplets, because the masks become contaminated with each use.
The team, from the University of Massachusetts Lowell and the University of California Baptiste, say the results provide evidence for why mask shape should be considered when examining protection and designing new masks.
Associate author Dr. Jinxiang Shi, associate professor of biomedical engineering at UMass Lowell, said it’s natural to think that wearing a mask, regardless of whether it’s new or old, should always be better than nothing. Our results show that this belief is true only for particles larger than five microns, but not for fine particles less than 2.5 microns in size.
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Three-layer masks are among the most recommended by health professionals to protect you and others from “Covid-19” infection. The inner layer is made of absorbent material, the middle layers act as a filter, and the outer layer is made of non-absorbent material.
In the study, published in the journal Physics of Fluids, the team developed a computer model of a person wearing a folded surgical mask.
They then looked at the behavior of aerosols, liquid droplets, and small particles that could remain in the air.
The model tracked where the spray landed on the mask and face, and whether it reached the nose or lungs.
The tool showed that when people wear masks, it changes the way air flows around the face.
The researchers found that air does not enter through the nose and mouth at specific points, but over the entire surface of the mask at low speeds.
They then looked at the filtration efficiency of the three-layer masks. And they found that when it is new, it can filter 65% of the particles, but when used, it can filter only 25%.
This means that a mask, when new, provides good protection, but wearing it multiple times can be worse than not wearing it at all.
The researchers believe this is because the pleats in the surgical mask affect airflow patterns and, when used repeatedly, change shape and reduce their effectiveness.
For future research, the team hopes to study how different shapes of the mask affect protection.
Source: Daily Mail
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