N95 Fit Test: Fill & Download for Free

A randomized study found that non-fit-tested N95 masks actually performed better. That’s strange, right?It’s particularly strange if we consider people’s strong claims about needing to fit test N95 masks. In the LA Times, a doctor claimed masks might be “worthless” without a fit test.An answer here on Quora makes an even stronger claim—that without training, they are worse than a piece of old cloth.My Face in a Fit TestFirst things first: here’s what mask fit tests are.The white tube pulls air from inside the mask, and the blue tube pulls air from outside the mask. The machine on the other end tests for particles down to .01 microns. The coronavirus is about .10 microns, so we’re talking truly tiny particles.Importantly, this happens while a real person (me!) is wearing the mask. That way we can know how well the mask is filtering the air, even after taking into account air leaking into the mask.The two masks I tried blocked more than 99% of particles.The third mask on the right is an old mask that I had worn for 11 days while biking in the sweaty Beijing summer. Even that old mask still blocked 98% of particles. (I give more data from long-term tests of masks here: Data Shows N95 Masks Can Last Longer Than Once Thought)But fit tests like this are helpful because sometimes people discover mask models that don’t fit them well. That happened to my friend Anna.On her face, the 3M 9211 only captured about 93% of particles.So the fit test helped her find a mask that blocked about 6% more particles on her face.Therefore You NEED a Fit Test?Entirely reasonable adults look at data like this and conclude that you NEED a fit test. For example, a group of entirely reasonable adults called the “United States Occupational Safety and Health Administration” requires workers who wear masks to get a fit test every year.Other reasonable adults take this logic a step farther. When wildfires were choking California, a Sacramento fire station started handing out N95 masks to help people protect themselves.Not long after, public health officials told them to stop handing out masks.Public health experts came up with lots of reasons, one of which was that masks need to be fit tested in order to be effective.Another headline at the time claimed N95 would actually harm people.The argument here is NOT that fit tests are helpful. That’s a no-brainer. But rather, the argument is that you NEED a fit test, or it’s basically useless (or even harmful).The Randomized TestBut what happens if we irresponsibly give people masks without a fit test? Scientists did just that!Researchers randomly assigned 949 doctors and nurses in Beijing to wear fit-tested or non-fit-tested N95 masks for 4 weeks during the winter flu season. Then they tracked how many of them got respiratory infections like the flu.Ideally, we’d want to compare masks to people wearing NO mask. But the ethics board wouldn’t let them assign some nurses to not wear a mask. So they did the next best thing: they tracked infection rates in hospitals where nurses don’t normally wear masks. After four weeks, here’s what they found.Fewer people wearing N95 masks got sick, similar to other studies. But here’s the real surprise: the non-fit-tested masks prevented infections just as well as the fit-tested masks! And if you look at the raw numbers, the non-fit-tested masks had slightly fewer infections (although the difference is not statistically significant).What Happens When You Give Masks to DummiesA very reasonable skeptic would point out that these are nurses—trained professionals. Even if these particular masks weren’t fit-tested, professionals already know how to wear masks. But if we were to give masks to untrained, regular people, it wouldn’t work.There’s data on that too! Researchers in Australia gave surgical and N95 masks to parents whose children were sick with the flu. Then they tracked how many parents got the flu.Remember, these are just regular parents, not professionals. NONE of the parents were fit tested.Yet the masks still prevented infection, even without a fit test, even without serious training. Another group of researchers found similar results with parents in Germany.Bottom line: Non-fit-tested N95 masks are effective in preventing infection—far from useless.Breathe safe!CaveatsJudging from comments on my prior writings, this data will anger some readers. And to those readers: yes, fit-tests are still a good idea! For people who have access to a $10,000 fit-test machine, by all means, get fit-tested.And it’s important to note that the recommendations for fit testing probably make more sense for industries that require people to use dangerous chemicals.I would sure as hell want a fit-test before my employer sends me to work with chemicals.And there are good reasons to screen for fit. Anyone with a beard will likely not pass a fit test.But let’s not confuse “it’d be nice to have a fit test” with “it’s useless without a fit test.”

No…Look, I won’t berate civilians for not understanding this, but you are all on the cusp of pissing me off. Please read why, and then pass this knowledge to your friends.The N95 mask first and foremost needs to be the proper size and fitted to you. I’ve been fitted yearly and I know my size (medium). I’ve tried being fitted with a small and large but they just don’t work. While they feel like they have a proper seal, there are tiny unsealed areas against my face in those sizes that render the mask useless for it’s superior protection. At that point I might as well just use a regular surgical mask.The N95 mask needs to be worn properly in order to be effective. I’ve seen civilians wear it upside down, with straps hanging down in front of them, or with straps placed wrongly on the head. None of you know what you’re doing. And if you are going to readjust your mask to momentarily breath better or cough, then why are you wearing it at all?The mask isn’t a magic save all device to protect you. If you need to wear an N95, you should be double gloved, wearing a full body protective suit, and eye protection. Wow, you wore a mask but you still failed due to touching any and everything around you to include yourself…We have an ongoing supply issue. The people who need the N95 are the healthcare workers working in close proximity to actual COVID19 patients. It’s utterly wasted on Karen sitting alone in her SUV on her ride to work at the office (where no one else is likely sick).Really, you’re just screwing over the people that need those masks. Unless you are fit tested, and have a real reason to wear it, and the threat is present at the time of wearing it all you are doing is wearing an expensive piece of filtered cloth that may not even be providing you with protection.Update: As has frequently been pointed out, I am apparantly not answering the question appropriately. The question assumes every worker in the United States has a mask and by extension has been fit tested, as well as being trained on its proper use. Ok, let’s run with that. (Giggling at the notion that all of that somehow changes the answer)There are 157,000,000~ Americans in the workforce. So each of them has 1 single-use mask that lasts 2 hours. Awesome… The average worker works an 8 hour shift, each of them needs 3 additional masks after that first mask just to complete 1 shift. Additionally, if you soil a mask (gets dirty, wet, or overly saturated with moisture) then that mask needs to be replaced, even if you only wore it for a minute.In a single week we need to have 3,140,000,000 masks of various sizes delivered to the right workers in the various sizes, assuming none of them have to use more due to becoming soiled…Now, do people understand why I might be getting frustrated? Stop trying to get around me on this, there are more things at play than what you understand. You can claim to have 2 PHDs in any other field, but if it’s not in this field those degrees mean nothing.

There’s a surprising amount of good, randomized data on this question—so much that it shocks me to see that the mainstream narrative is that masks are NOT about protecting the wearer:All the big organizations—WHO, CDC, ECDC have been saying this, yet not citing evidence.Maybe they’re citing intuition? It certainly is intuitive. Surgical masks are not tight-fitting.It’s not just intuition. It’s data. Researchers have tested using mask fit-tests, like the one I’m doing here. This setup tests what percentage of air is going through the mask versus leaking around the sides while a person is actually wearing the mask.Those fit tests routinely find that surgical masks score lower than N95 masks. For example, doctor and Quora writer Richard Saint Cyr MD fit-tested a surgical mask against five N95 masks. Most of the N95s managed to get more than 90% of air through the mask (rather than leaking around the sides), whereas the surgical mask only got 63%.But that’s just one person. When researchers fit-tested surgical masks on 21 people, they found a median fit effectiveness of 80%. That’s lower than a study of N95s that found 99.5% fit effectiveness.Bottom Line 1: Surgical masks don’t fit as well as N95 masks.Yet Surgical Masks Still Prevent InfectionsI find that people have an odd all-or-nothing image of how disease works. The logic works like this: if some intervention isn’t perfect, it’s worthless. Can you spot that logic in these examples?An infectious disease expert at the University of Texas said that touching a mask could make it useless.Similarly, the Los Angeles Times printed an opinion letter claiming that N95 masks are “worthless” without proper fit testing.There’s some truth to these claims. We shouldn’t be touching our masks, and it’d be great if more people could personally fit-test masks like I did. (Unfortunately, that fit-test machine costs $10,000.)Tests of Imperfect MasksSo how perfect do masks have to be to have a meaningful effect on preventing infection? Can those 80% surgical masks prevent people from getting sick?But there’s a problem. If we want to test whether masks work, we need to randomize some people to not wear a mask. But it’s hard to find studies with a “no mask” comparison group because how are scientists going to force people to be around sick people without a mask?But wait! There is a way. When people in our own families get the flu, some people (most people?) don’t wear masks. Thus, researchers could defensibly randomly assign people to wear masks or not.And that’s exactly what researchers in Australia did. They gave surgical masks to parents taking care of their children, who were sick with the flu.Then they tracked how many parents got the flu. One important thing to note: the sick children didn’t wear masks. It was only the healthy parents. So this is a test of protecting healthy mask-wearers, not of keeping sick people’s germs in.When the data came in, 16% of unmasked parents got sick, compared to 8% in the surgical mask group.Perhaps not surprisingly, the masks only worked for people who actually wore them. There was no benefit among people who often forgot or just gave up on wearing the mask. So yes, masks are useless if people don’t wear them. Shocker!But here’s the far more interesting conclusion from that study:Bottom line 2: Masks work, even if they don’t fit perfectly, even if they’re worn by us regular, unprofessional, non-fit-tested dummies.It Gets Crazier: Surgical Masks Reduce Infection as Much as N95 MasksThe data is even wilder than that. What I didn’t tell you was that home study also tested N95 masks. They randomly assigned some parents an N95 mask like the one I’m wearing here.(OK, they used “P2 masks,” but P2 and N95 masks are essentially the same thing.) We know N95s fit better, so they they prevented infection even better than surgical masks, right?The mighty surgical mask! Surgical masks prevented infection as well as N95 masks. That is genuinely surprising.Well That’s Because Those Dummies Didn’t Know How to Wear N95 MasksN95 masks are fairly sophisticated. Professionals like nurses and engineers who work with dangerous chemicals are required to do fit-tests every year.Fit-tests are important, right? These parents were non-professional, un-fit-tested mask n00bs.So let’s bring on the professionals! Researchers have tested the same thing with nurses—people who are specifically trained to wear masks. Researchers in California randomly assigned 2,862 nurses to wear surgical masks or N95 masks.Then they tracked who got infected with the flu.There was no statistical difference in infection rates. If anything, the surgical mask group was infected slightly less.And lest any readers out there think this is something about careless Americans, a study with Canadian nurses found the same thing.Bottom line 3: Several randomized studies have found that surgical masks prevent respiratory illness as well as N95 masks.OK, I’ll Believe You on Surgical Masks, But These Cloth Masks Are JunkThese studies are all with medical-grade masks. So maybe skeptical readers out there will grant me that it works for surgical masks, even though they don’t seal completely. But most people during the coronavirus are just wearing flimsy cotton masks.And here’s where we get to the edge of knowledge. The data for homemade masks is the weakest.Because homemade masks weren’t on scientists’ radars for the last 50 years, we don’t have good randomized studies tracking infection with homemade masks. Thus, the evidence we’ve got is mechanism data—do masks filter viruses?Years before the COVID crisis, researchers tested homemade cloth masks by shooting viruses (yes, real viruses!) at homemade cloth masks and seeing what percentage the masks could block.And the data proved the skeptics right—the homemade masks didn’t capture as many viruses as the surgical masks. But they did manage to capture just over 50% of the virus particles.So DIY masks capture some virus particles, but these flimsy cloth masks are too leaky, right?Wrong! Another team of researchers in the Netherlands (again, pre-COVID) fit-tested homemade cloth masks. This team used cotton dish towels, rather than the cotton T-shirts the other team used. Here’s what their fit test looked like.That researcher looks extremely enthusiastic, but I’m pumped about this data because it gets at the debate America is having right now. Remember, this is about keeping tiny particles out of the lungs of a healthy, uninfected person. It’s a flimsy cotton mask tested while an actual person is wearing it (actually, while 28 adults wore the masks).Not bad, dish towel! Again, the homemade mask kept fewer particles out than the professional masks, but still much better than nothing. (You’ll notice yet again that the surgical masks averaged around 80% on fit effectiveness—lower than N95 masks).Bottom line 3: Homemade cloth masks capture a significant percentage of virus particles, even while real people are wearing them and even after taking into account leakage.So yes, even imperfect masks can have a meaningful effect on preventing respiratory infection. We just need to wear them.Breathe safe!P.S. Fit-Test or Bust?Remember that claim that masks need to be fit tested or they’re junk? Researchers tested that too! They randomly assigned nurses to get fit-tested for N95 masks or just receive N95 masks without a fit test. And it turns out, infections were just as low in the non-fit-tested group.P.P.S. Do Masks Make People Feel Invincible?Have you ever heard people argue that masks are actually dangerous because they make people overconfident and therefore take more risks?Researchers just tested that. The data showed the opposite: masks made people slightly more cautious.