We all need to wear masks in public spaces to prevent the spread of COVID-19 – but not all of them are created equal.
And not much was known about how effective each was at stopping respiratory drops.
That is, until Duke University researcher Dr. Martin Fischer came up with a simple test to measure it.
The experiment, published Friday in the journal Science Advances, tested 14 different types of masks and was inspired by a request from Fischer’s colleague Dr. Eric Westman, who works with Cover Durham, an initiative to distribute reusable face masks to those in need. Westman asked if anyone at the school could assure him that the masks he received as donations were effective.
To test the coverings, scientists visited a black box with a laser and a mobile camera and four testers had to try the 14 donated options. Wearing each mask would speak to a tester in the direction of the laser beam in the box and said the sentence “five stay healthy, people”. A camera recorded the number of respiratory drops put through the speech, and an algorithm determined how many drops were leaking through the face mask.
“It was about setting up a simple measurement technique that could be reproduced,” Fischer told The Post.
And while he does not advocate for a specific mask, Fischer – who even wears a basic cotton version – says the overarching point of the study is that many of the varieties are quite effective. But it’s better if you’re wearing a real mask than something you look like as a bandit trying to stab a bank in the Wild West.
Here’s a breakdown of face masks that Fischer and his team put through the paces, from the heavily sealed medical N95 mask to the flashy neck gear.
The best
1. medical n95 masks
It is no wonder that the invented “3M 1860 Surgical Mask and Particulate Respirator” is worn by health care professionals: It was the most effective of the bundle on the logarithmic scale of the study.
2. surgical mask
This disposable surgical mask was the second most effective variety, ranging from zero to 0.1 in terms of the particles scattered by speech when wearing one.
3. polypropylene and cotton
The synthetic material polypropylene, laid in two layers of cotton, was the third best.
4. polypropylene front mask
This mask made with two layers of the synthetic material was just less than it was made with both cotton and polypropylene.
5. cotton mask with ribbons
The next six cotton masks all performed around the same level, which Fischer said shows that variables matter. “It depends on how loud you speak, and how well it fits in your face,” or if facial hair causes a looser fit, he said.
6. two-layer cotton with ties
Right behind the green band mask was another cotton version with two layers, and straps that went over the bottom and tied behind the ears.
7. valved n95
N95 masks with exhalation valves are designed to protect the user from breathing harmful materials, not necessarily vice versa, which could have contributed to his performance.
8. hand-sewn cotton
This cotton mask was sewn with the popular “Olson” pattern, which is available online.
9. Mask ‘MAXIMA AT’
A pleated cotton variety from North Carolina-based company Hudson’s Hill was essentially tied with the equivalent-looking single-layer cotton mask to the left.
10. cotton with one layer
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, Fisher said.
11. pleat two-layer cotton
This two-layer cotton pleated style mask, performed just a little less than its other similar styles.
12. cut
A mask made from what appears to be a tee-shirt knit (Fisher was happy to point out that the researchers are not textile experts) had more of the variability of drop projection than other styles.
13. bandana
Complemented by celebrities like Johnny Depp and Kristen Stewart, the folded bandana has become a chic cover option, but it’s basically useless, multiple studies – including Duke’s – have found.
The worst
14. neck gaiter
The hair tested stretchy gaiter (a style preferred by circles) was worse than the mask completely before going, and it was shown that the larger particles became smaller parts so that they could slide out of the sides more easily.
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