COVID-19: US study shows fleeces and bandanas make bad masks


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In scientific jargon, “We have demonstrated a simple optical measurement method to assess the effectiveness of masks in reducing respiratory droplet transmission during regular speech. Our measurement setup is inexpensive and can be designed and used by non-experts, allowing rapid evaluation of mask performance during speech, sneezing or coughing. ”

The 14 masks tested included a fitted N95 respirator, an N95 valve respirator, surgical masks, several types of cotton masks, a poly / cotton blend mask, a knitted mask, a bandana and a fleece.

The results showed that no droplets entered the fitted N95 respirator. The surgical mask was the second best. Cotton masks worked to varying degrees with the N95 valve mask being among the best cotton masks.

Knitted masks did not perform well, but using a bandana was worse The fleece used as a mask was actually worse than no mask at all because the droplets were broken down by the fleece and spread out more .

“We noticed that speaking through some masks (especially the fleece of the neck) seemed to disperse the larger droplets into a multitude of smaller droplets, which explains the apparent increase in droplet count compared to no mask in this case, ”the report says.

The relatively poor performance of the N95 valve respirator – given that the fitted N95 respirator had perfect results – was attributed to the exhalation valve, which opens for a strong flow of air to the outside.

“Although the valve does not compromise the protection of the wearer, it can decrease the protection of those around the wearer. In comparison, the performance of the fitted, valve-less N95 mask was much better, ”the report states.

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