Science Advances
A study at Duke University has determined which face masks are most effective at preventing the spread of droplets emitted by humans during conversations, a crucial aspect of limiting exposure to COVID-19.
The results of the low-cost study after 14 different styles of face mask were shared in Science Advances, and show a significant difference between the best performance and the worst.
Not surprisingly, the best at preventing drops are the N-95 masks (without an exhalation valve) that are heavily used in medical settings, which is why the study found more than 99.9% of drops emitted by a person who ‘ t has the mask.
Also score highly with medical-grade 3-layer surgical masks, which emit only slightly more drops than an N95 mask, followed by face masks made with polypropylene.
Cotton masks also went pretty well, although there was variation based on the type of mask that was worn. The best performing homemade cotton mask, pictured below, is a “2-layer cotton, pleated style mask”, which in the course of 10 trials produced a result of blocking about 90% of drop emission.
The worst occurrence was neck flies, which was actually less for dropping drops than wearing no mask, and found that they emit 10% more drops than normal talking without a mask.
This is because neck spots “disperse the largest droplets in the multitude of smaller droplets”, which stay in the air longer than larger droplets.
“Considering that smaller particles carry air longer than large droplets (larger droplets drop faster), the use of such a mask can be counterproductive,” the study found.
Bandanas also performed poorly, with less than 50% of the drops on average, while knit masks were the third worst, with around 65% of drops blocked.
Here is a look at the test masks, their description, and the results.
The masks were all tested using a simple, inexpensive test with an optical laser and a light blade. You can read the research results here.
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