The best and the worst face masks, according to scientists
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By KIRSTEN FLEMING and CATHERINE KAST
We all need to wear masks in public spaces to prevent the spread of COVID-19 — but not all of them are created equal.
Duke University researcher Dr. Martin Fischer has developed a simple test to measure which masks keep you safe, and which are just for show.
The experiment, published in the journal Science Advances, tested 14 different types of masks. It was inspired by a request from Fischer’s co-worker Dr. Eric Westman, who works with Cover Durham, an initiative to distribute reusable face coverings to those in need.
Westman asked if someone at Duke could come up with a way to gauge the power of different masks — in order to assure him that the ones he received as donations were good enough to be handed out.
To test the coverings, scientists outfitted a black box with a laser and a cellphone camera and had four testers try out the more than two dozen distinct options donated to
Cover Durham.
Wearing each mask, a tester would speak in the direction of the laser beam inside the box, saying the phrase “Stay healthy, people” five times.
A camera recorded the amount of respiratory droplets set off by the speech, and an algorithm determined how many droplets had leaked through the face covering.
“This was about setting up a simple measurement technique that can be reproduced,” Fischer told The Post.
And while he doesn’t advocate for any specific mask, Fischer — who wears a basic cotton version himself — says the overarching point of the study is that many of the varieties are pretty effective.
But, he found, you would be better off wearing a real mask than something that makes you look like a bandit trying to stick up a bank in the Wild West.
Here’s a breakdown of face coverings Fischer and his team put through the paces, from the strong, sealed medical N95 mask to the flimsy neck gaiter.
14 NECK GAITER The stretchy gaiter tested here (a style beloved by runners) was better than forgoing a mask completely, but was shown to break the larger particles into smaller ones, allowing them to slip out of the sides more easily.
5 COTTON MASK WITH TIES
The next six cotton masks all performed around the same level, which Fischer said shows variables matter. “It depends how loud you speak, and how well it fits around your face,” or if facial hair causes a looser fit, he said.
13 BANDANA Adored by celebrities such as Johnny Depp and Kristen Stewart, the folded bandana has become a chic covering option, but it’s basically useless, multiple studies — including Fischer’s — have found.
7 VALVED N95
N95 masks with exhalation valves are designed to protect the user from breathing in harmful materials not necessarily the other way around, which may have contributed to its performance.
2 SURGICAL MASK This disposable surgical mask was the second most effective variety, ranging from zero to 0.1 in terms of the particles spread from speaking while wearing one.
12 KNITTED
A mask made from what appears to be a T-shirt knit (Fischer was keen to point out the researchers are not textile experts) had more variability of droplet projection than other styles.
10 SINGLE-LAYER COTTON This one-layer mask performed better than one with two layers, which should serve as a reminder of the variables in the experiment and in life, said Fischer.
1 MEDICAL N95 MASK No wonder the fitted “3M 1860 Surgical Mask and Particulate Respirator” is worn by health-care workers: It was the most effective of the bunch on the study’s logarithmic scale.
9 ‘MAXIMA AT’ MASK
A pleated cotton variety from North Carolina-based company Hudson’s Hill was essentially tied with the similar-looking single-layer cotton mask to the left.
6 TWO-LAYER COTTON WITH TIES
Right behind the green tie mask was another cotton version with two layers, and straps that went across the bottom and tied behind the ears.
4 POLYPROPYLENE APRON MASK This mask made with two layers of the synthetic material was just marginally worse than the one made with both cotton and polypropylene.
3 POLYPROPYLENE AND COTTON The synthetic material polypropylene, laid in between two layers of cotton, was the third best.
8 HAND-SEWN COTTON
This cotton mask was sewn using the popular “Olson” pattern, which is available online.
11 PLEATED TWO-LAYER COTTON This two-layered cotton pleated style mask, performed just slightly worse than its other similar styles.