Covid-19: why the mask alone is not enough to protect you

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Due to the Covid-19 epidemic, putting on a mask before leaving home has become a true reflex. And for good reason: this barrier gesture has become mandatory. However, researchers have just shown that it is not enough on its own: if the use of a mask allows to limit the risks of contamination, it must be combined with social distancing to be fully effective.

Although this measure is essential to limit the risk of contamination by Covid-19, it is not enough. This is demonstrated by a new study in the journal Physics of Fluids, which highlights the importance of social distancing.

As part of this work, American researchers tested the effectiveness of five types of masks: a classic fabric mask, a two-layer fabric mask, a two-layer wet fabric mask, a surgical mask, and an N95 mask, that is, the American equivalent of the European FFP2 mask used by medical personnel. To do this, they used an air generator that could mimic human coughs and sneezes. The objective? Encourage a situation in which two people stand face to face at a short distance.

The scientists found that each mask significantly reduced the number of droplets that spread. But they also noticed that at distances of less than 6 feet or 1.8 meters, enough droplets to cause Covid-19 contamination had passed through several of the tested masks. If the N95 mask had stopped, for example, 100% of the drops, the classic fabric mask had allowed about 3.6% to pass through. "Wearing a mask offers substantial but not complete protection," said Krishna Kota, a co-author of the study.

Findings that prove, if necessary, the importance of social distancing in addition to the use of a mask. "One mask certainly helps, but if people are very close to each other, there is always the risk of spreading or contracting the virus. It is not just the masks that will help. It is the two masks and the distancing," said the scientist.

Therefore, the study authors recommend "minimizing or avoiding face-to-face or head-on human interactions, if possible." It is also essential to respect barrier gestures, such as hand washing or ventilation, to limit the risk of contamination.

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