What you need to know about 13 common mask types
Every day, we seem to have more scientific data about what type of actions best protect us (and others) from COVID-19. When scientists look at the effectiveness of masks, they consider both the safety of the wearer and those around them. Some of the latest insights are from an August 2020 study by researchers from Duke University’s physics department, who looked at the capacity of 14 face coverings and a no-mask control to minimize transmission of respiratory droplets when the wearer was speaking.
The researchers used a simple, low-cost measurement of the effectiveness of different facemask types, and focused primarily on the effectiveness of the testing method, rather than the impact of specific masks in avoiding COVID-19 infection. The study used a proven optical measurement method: an enclosure into which subjects could speak, outfitted with a green laser light that illuminated droplets and a cell phone camera that allowed the team to capture video and count droplets via a simple algorithm.
The tests looked at droplet transmission only when the subject was speaking and not other methods of transmission such as coughing or sneezing. The study had a sample size of only one for all masks, and only four for some of the masks (very uncommon in scientific research), and the team stressed that “inter-subject variations are to be expected, for example due to difference in physiology, mask fit, head position, speech pattern, and such.”
More research on this topic is necessary to definitively say which masks are most effective, particularly in the realm of cloth and other types of homemade masks. However, Stacker has found this study to be a useful jumping-off point for discussing 13 common masks and other covering types used by Americans across the country. The masks tested in the Duke University study are organized in this story from least protective to most protective, according to the study’s results. Our slideshow excludes the no-mask control from the study.
Continue reading to learn more about the latest research on this topic.
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#13. Fleece gaiter
Gaiters have become increasingly popular as a face covering during the pandemic. But despite their stylish look, and capacity for warmth in winter, neck fleeces, aka gaiters, were shown in the Duke study to separate large droplets into smaller ones that remain airborne longer.
But another study from a mechanical engineering professor at the University of Wisconsin–Madison noted that gaiters with both a nose piece and an elastic cord to create a more-snug fit actually performed better than other options.
Until we have more data, you may want to save gaiters for snowboarding, skiing, and surviving brisk wintry days, unless you’re laying one over a more-protective face covering.
The study found that double-layer bandanas, though better than nothing, only filtered about 50% of droplets. WebMD called them a “last resort.” This option might make sense if you run out of the house without your usual face covering, but have a bandana handy.
Knitted masks performed more poorly in terms of droplet transmission than any other option except the no-mask control and bandana and fleece gaiter coverings. One option is to knit or crochet a mask, then add a polypropylene layer inside to up the protection level.
#10. 1-layer pleated cotton
Though one-layer pleated cotton masks performed better than several other options, another study noted that more layers equal more protection from droplets, with a researcher recommending that “you probably need at least three layers.” Scientists also note that gaps between the mask and the face decrease the capacity of the mask to prevent COVID-19 infection, so choose a mask where the elastic creates a snug fit. If it doesn’t, one option is to fold over a bit of the elastic so it does, then stitch into place.
#9. Maxima AT
The single-layer Maxima AT mask used in the study is constructed with one layer of breathable polyester fabric. Its effectiveness landed near the middle of the grouping.
#8. Olson-style cotton
The “Olson-style” mask is a two-layer cotton mask that’s contoured rather than pleated, with elastic loops that go over the ears. This is one of the most popular designs used by DIY mask creators, and patterns are now readily available.
#7. Valved N95
Because valved N95 surgical masks allow outward airflow from the wearer to others in his or her vicinity, protection exists primarily for the wearer. Because of this, several airlines are now banning customers from wearing this type of mask. Fitted N95 masks without a valve do a better job of protecting everyone.
#6. 2-layer pleated cotton
Two-layer pleated cotton masks are one of the most common options from DIY makers. Scientists have reported that tighter weave, aka thread count, cotton does a better job of filtering droplets. Studies have shown that multiple layers improve effectiveness, but that mask fit and user behavior also factor into the equation. NIOSH (National Institute for Occupational Safety and Health) reported “difficulty achieving a proper fit” for respirators (not masks) with earloop designs, preferring those with headbands.
Because of the effectiveness of polypropylene in trapping droplets, the swath option was one of the more successful ones in protecting the wearer and those around them. But a proper fit is key: Those who choose this type of protection need to take care to avoid gaps between the covering and the face. Fabric construction is also important: Polypropylene spunbond has a filtering efficiency of up to 6%, better than many other materials.
One of the benefits of polypropylene, used for the study’s two-layer apron-style masks, insertable filters, and the previously-mentioned swaths, is that the material has an electrostatic charge that traps droplets. Other materials do not retain that charge when you exhale.