COVID Notes #8 (Special Masks Edition)

CARDIFF, UNITED KINGDOM - APRIL 03: A box of N95 surgical face masks on April 03, 2020 in Cardiff, United Kingdom.The Coronavirus (COVID-19) pandemic has spread to many countries across the world, claiming over 70,00... CARDIFF, UNITED KINGDOM - APRIL 03: A box of N95 surgical face masks on April 03, 2020 in Cardiff, United Kingdom.The Coronavirus (COVID-19) pandemic has spread to many countries across the world, claiming over 70,000 lives and infecting over 1 million people. (Photo by Matthew Horwood/Getty Images) MORE LESS
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This is an uncharacteristic post. But I realize that a lot of people are looking for information like this. So I am sharing what I’ve learned on this topic.

For all the polarization and argument over masking, there’s much less discussion or guidance about what kind of mask you should wear. At the beginning of the pandemic any mask was better than none. High quality masks needed by health care workers and first responders were in short supply. But that hasn’t been the case for a very long time. High filtration masks are widely available at relatively low cost. And you should be wearing one.

Cloth masks are better than nothing. But that should not be your standard. Even if you’ve got it hostage-taking tight around your face it’s still providing much less protection than a real filtration mask. Surgical masks are fine. But a high filtration mask provides a much higher level of protection than those too. You now have the ability to give yourself a high level of protection even if you’re somewhere where others aren’t masking or aren’t masking well.

What’s A Good Mask?

The American standard for a high filtration masks is the N95. But that’s a NIOSH standard of filtration, not a specific mask. So they come in various shapes and styles. KN95s are a similar standard from China and the KF94 is a similar standard from South Korea. The KN95 is a good mask. The problem is that the market is flooded with counterfeits. So it’s hard to know whether you’re getting a mask that actually provides the level of protection you need. I generally warn people off these just because of the counterfeiting issue. But if they’re real KN95s they’re good too.

The South Korean KF94 masks are manufactured in South Korea. For whatever reason there doesn’t seem to be the same problem of counterfeiting. If they say Kf94 and they are made in South Korea you can be confident they’re legit. They create a small open space in front of your face which makes them feel more comfortable for many people. Obviously, the comfort aspect is largely subjective. It can depend on the size and shape of your face. KF94s are my go to, basically all I wear at this point. They seem like a really good mix of filtration, fit and comfort. That’s my experience and that of many other people. But again, the comfort aspect is subjective.

There’s also a European standard called the FFP2, which is comparable to the N95. But for whatever reason you seldom see them for sale in the US.

I’ve heard various things on the comparative effectiveness of these different standards. It seems fair to say that the official versions of these (not counterfeits) are at least in the same ballpark of effectiveness if they may vary on exact filtration levels. An N95 is still treated as the gold standard. But I don’t know how much that higher rating is backed up with real world tests or just branding.

Recently I have found the Aura N95 mask sold by 3M. It’s the most comfortable n95 mask I’ve found and for me it provides a good seal. (I have a relatively large head so that plays into it – no jokes, please.) At the risk of stating the obvious, when I refer to ‘comfort’ obviously I don’t mean, “Man, I love wearing this mask!” I’m referring to something you can wear consistently and effectively over time.

As I noted above, N95 is a standard rather than a particular mask. So as long as it’s an N95 from a reliable vendor it’s really a matter of finding one that is comfortable enough to wear as long as you need to wear it and one that seals well and consistently.

A key player on this is Abraar Karan, a physician affiliated with Brigham and Women’s Hospital in Boston and Harvard Medical School. He’s become a major evangelist for high filtration masks and is part of the #BetterMasks initiative. You can follow him on Twitter and I link to an article by him in the resources below.

How Do I Know It’s Working?

To provide robust protection the mask has to have a good seal to your face. Otherwise air isn’t going through the mask and filtered. It just goes around it.

How do you know it’s a good seal? Good question!

This is one of the harder things to get good information about. I have links below to various CDC pages that provide guidance but I have found them less user-friendly than they should be. So here are some starters to know you’re on the right track.

If you wear glasses and they’re getting fogged up that’s a pretty good indication that you don’t have a good seal. The air you’re exhaling is going out around the mask and going up behind your glasses.  That’s air going out but it’s probably a good indication the incoming air is also going around rather than through your mask.

Try this.

Check the mask to see if it seems clearly seated against your face. 

Inhale and exhale and see if you can feel exhaled air coming around the edges of the mask. 

Try to do a negative and positive pressure test. If you are pushing air through the mask, rather than around it that will create negative (inhale) and positive (exhale) pressure on the mask. When you inhale, if you’re exerting some negative pressure, you should be able to see a bit of inward buckling on the mask. Because again, it is being pulled inward by the negative pressure created by your inhalation. 

How to make sure you’re mask is fitted well is one of the most difficult things to get good information about. (As I said, there’s a CDC link below which covers it but I find it hard to follow.) There are lots of CDC articles about how you really need an official fitting. And you probably do by some standard – especially if you’re working in a health care setting. But who of us has the ability to get an official fitting? So these are just some basics that should help. If you find expert guidance that is clear and works for you, definitely go with that.

My experience is that for the best seal you really need to have a mask with the double straps that go over your head rather than the kind that go around your ears. But it’s up to you where to draw that line on effectiveness and comfort. At a minimum, if you need to be around someone you know has COVID, for that I would definitely try to use one of those double strapped masks.

What I generally tell people is to use either the KF94 (ear loops) or the Aura 3M n95 (two straps). To me those are a good mix of high filtration and comfort.

More reading? The first place I’d go is the StatNews article at the top of the resource list. I have other links below on how to choose and use masks and where to buy them.


Along with vaccine rollouts, the U.S. needs a National Hi-Fi Mask Initiative, StatNews, By Abraar Karan, Ranu Dhillon and Devabhaktuni Srikrishna, January 7th 2021.

CDC: NIOSH-approved N95 Particulate Filtering Facepiece Respirators, September 2021.

CDC: Documents on Fit Testing.

CDC: User Seal Check.

Wirecutter: Where to Buy N95s, KN95s, and Surgical-Style Masks in 2021. December 3rd, 2021.

Project N95: Site that vets merchants selling masks to make sure they’re genuine, not counterfeit, etc.

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