The best face mask is one that fits

February 1 (Vox) – My favorite face mask is a sleek black cloth number — it goes with everything, it doesn’t chafe my face, and it’s sold in a relatively affordable three-pack, so I always have a backup. I have a whole collection of cloth masks, like you probably do too, cobbled together at random, in bright colors and patterns, generally homemade by an assortment of people in my life.

Yet, as we’ve slipped into allowing our face coverings to project our tastes while they protect us, there’s another element of style that’s often forgotten: fit. And fit is incredibly important when it comes to how effective our masks are.

Tons of celebrities have been seen out with their masks underneath their noses. Notably, members of Congress who promote masking up have been seen pulling up their sliding masks in public.

Cloth masks sometimes lend themselves to poor etiquette: Rep. David Cicilline (D-RI) slipped his down to sneeze into his hand on C-SPAN, which is, to put it plainly, horrifying. House Speaker Nancy Pelosi is known to have masks that match her outfits but was once photographed in a conversation with George Floyd’s brother, mask hanging down below her mouth. And soon after his inauguration, President Joe Biden’s mask slipped down his face in the midst of signing an executive action related to Covid-19. It happens to the best of us. Walk around anywhere in pandemic America, and you’ll surely encounter people fiddling with their masks.

But in order to truly protect you, cloth masks need to have a snug fit. And wearing a well-fitted mask might be more important than it’s ever been in the pandemic. As previously reported by Julia Belluz for Vox, a more contagious new variant of Covid-19, known as B.1.1.7, that’s now spreading around the world, should make us even more cautious about our risk of exposure to the virus, especially in indoor spaces.

Mask fit really matters

Proper mask-wearing remains a key factor in preventing the transmission of the coronavirus. A mask slip can leave the wearer extremely vulnerable, as the nasal passage is a common entryway for the virus to get into the body. According to a study in Nature Medicine, the virus attaches to certain proteins found in the nasal passage. There are actually more of these proteins in the nose than in the lungs, making an exposed nose a serious threat. You don’t want any viral particles getting to your nose, so it’s imperative that your mask has a tight fit.

Cloth masks are still fine for the general public to use, experts tell me, so don’t feel like you have to run out and buy a medical-grade mask like an N95. We think about what our masks look like every day, but we are largely ignoring the importance of the proper fit. There’s not enough emphasis on what makes a mask well-fitted and effective — we’ve gotten distracted with design, when really we need to be worrying about how comfortable our masks are and whether or not they are secure enough to rely on.

The Respiratory Protection Engineering Task Force, a research group based out of Cambridge University, investigates the efficacy and improvement of civilian face masks and fabrics. “What we found through our research is that the actual filtration material is not as important as fit. In order to get any benefit from a high filtration material, you have to have fit,” Eugenia O’Kelly, a PhD student who heads the group, said. O’Kelly emphasized that without highly specialized machinery, there is no way to be 100 percent sure your mask fits, but did have tips for improved fit and protection.

According to her team’s tests, double masking can be helpful. “Keep in mind, you do not end up numerically doubling your protection by layering masks. I have seen a lot of this type of ‘math’ online, but unfortunately, this is not how depth filtration works,” she said. But doubling up can ensure you get a better seal around the nose and mouth than one mask alone that might be a bit too loose.

O’Kelly says there are two methods scientists use to find out if a mask fits. “You can have quantitative fitting and qualitative fitting. In quantitative fitting, you are measuring the amount of particles inside and outside of the mask,” she said. Most surgical masks don’t fit tightly enough, or are made of material without sufficient filtration, so they won’t pass.

Quantitative fitting can be expensive because it requires specialized hospital equipment. “More common is qualitative mask fitting,” she said, for which her team is experimenting with using aroma diffusers as a test. If you are wearing a mask and can taste the particles through it, it’s a sign that your mask is ill-fitting.

In order to identify if your mask is good at protecting others, O’Kelly recommends avoiding masks with the following characteristics:

Thin material: If you can see any gaps between the fibers when you hold it to the light, that is a sign that viruses can get through.

Single-layer: If your mask only has one (or even two) layers of fabric, the filtration is probably not high. The best masks have multiple layers or have a pocket to insert a filter, such as a PM 2.5 or HEPA filter.

Poor fit: Fit is very important in a mask’s success, as you can read about in this recent study. You may not be able to get a mask that fits you perfectly, but the more and larger the gaps you see, the poorer the fit is. This may be more important when protecting the wearer than others.

Discomfort: If the mask is very uncomfortable, you may be less likely to wear it correctly, and more likely to touch the outside of the mask or adjust it while out and about.

So how should a mask fit? “The mask should be a good fit over the nose and mouth, but not overly tight to impair breathing. It is not intended to filter out all the air one breathes, but intended to hold back droplets from our mouth from spreading in the air,” George Abraham, the chair of the American Board of Internal Medicine’s Infectious Disease Board, tells me.

There’s not a lot we can do to prevent a mask from falling down — except maybe try to find a mask that fits better.

O’Kelly also recommends doing a fit check, although there is no reliable way to currently assess the fit of fabric masks. “Move your hand around the edges of the mask where it makes contact with your skin and see if you can feel any air. If you feel the air, there is a gap,” she said. But just because a mask has a gap does not mean it’s totally ineffective. It just means it’s not providing the maximum level of protection possible. According to O’Kelly, a fabric mask with fit issues can protect the user from over 50 percent of particles, and well-constructed fabric masks with gaps still can filter over 75 percent of particles.

In a Consumer Reports article, William Schaffner, a professor of medicine in infectious diseases at Vanderbilt University School of Medicine, recommends tightening your mask if it slips off your nose. You can adjust the strings and make sure there isn’t any space for air on the sides. Our best bet is selecting a mask that fits properly: snug around the nose and mouth without gaps at the sides. A mask with a wire nose bridge can help your mask mold to your face. The Respiratory Protection Engineering Task Force’s studies have found that a metal nose band can improve fit. However, in less structured or elastic masks, that nose band can also harm performance, so the user has to make a judgment call.

But shouldn’t we just get N95s?

As comforting as it might be that cloth masks are sufficient, the United States is far behind countries like Austria, where the government provides FFP2 masks to citizens, and Taiwan, where the government has been providing citizens with high-quality masks that are probably going to fit better than some of the cloth masks in circulation. Why can’t the same happen here in the United States?

The argument for the government to supply masks is not new. It might do Americans well to have better PPE, but there are a lot of caveats that come with the use of heavy-duty masks like the N95. In an email, Abraham told me that it would be difficult for the government to make sure that everyone had an effective N95. “The wearer needs to be ‘fit-tested’ so that the mask being used is not leaking but forms a good seal on the face, or else the ability of the mask to filter is lost,” he wrote. “As a practical reality, that is not consistently possible with the general public.”

There are ways to test the N95 — “you could place both hands around the rim of the mask, once on the face, and blow hard into it. If you feel air on your hands, you know the mask is not a tight fit,” Abraham explains. But according to experts, it is also not 100 percent accurate.

The N95 masks are a must for health care workers because they’re great for long exposure situations, but they might be excessive for short-term use, according to Abraham. An N95 mask might be more appropriate for a long plane ride, for example, instead of a quick run to the grocery store. “The use of the mask would be inconsistent, without doing a fit check every time,” Abraham said, and it would be “cost-prohibitive and accomplish little.” The government couldn’t regulate the N95 use of every civilian, and the respirators would be rendered useless if not properly fitting.