Face masks for DEFCON

Testing which ones work well.

Next month will be the annual DEFCON hacker/cybersecurity convention in Las Vegas, the biggest of its kind. They won’t be checking vaccine status, but they will be requiring masks. Since Omicron variants like BA.5 are highly infectious, people are likely to care about efficacy of masks, in contrast to past events where people primarily cared about compliance. Therefore, I did some simple testing of the efficacy of masks, to help give some perspective on the topic.

The TL;DR is that if you care about efficacy:

• Throw out your cloth/surgical masks and use N95 instead — the difference is huge.

• Get one that seals (fits) your face with no gaps — almost certainly a behind-the-head mask instead of behind-the-ears.

• Get one that fits comfortably for long term use.

• You are probably going to limit your choices to what’s socially acceptable (disposable N95 rather than plastic).

I recommend you start with something NIOSH N95 certificated like 3M Aura N95 and move on from there until you find one that seals comfortably on your face. You will probably have to try out multiple masks, so do this with friends, with each buying different mask (often $30) for trials, then pass them around to so that each person can try multiple masks. Finding the best fit/comfort can be difficult.

Methodology

The standard for medical use, for maximum efficacy, is a fit tested N95 elastomeric respirator.

Their requirements aren’t just the type of mask but also regular checks to see if it fits without any gaps. Small gaps that let air in lead to big differences in efficacy.

The fit tests work by spraying either saccharine (sweet) or bitrex (bitter) in aerosol form into a hood around your head. If you can taste it through your mask, then the mask isn’t working.

You can watch the training videos on YouTube to see how this works.

I bought two of these mask fit test kits. They cost around $350 each. I first tried the sweet version, but wasn’t sensitive enough (I drink too much diet Coke desensitizing me, probably). I had to switch to the bitter version.

I followed their instructions, specifically testing:

• deep breaths

• turning head side to side and up and down

• bending over

• talking

At the end of their tests, I added more more step:

• smiling, grimacing, and winking

Only one of my masks survived that last test, so I shoved a pen between it and my face as the last step, to force a failure. In other words, all masks were tested until they failed, even if they passed the standard tests.

Note that this is a qualitative not quantitative test. It’s testing whether or not I can taste the bitrex, and not a measure of how many particles get through. It’s pretty binary, I either tasted it or I didn’t, with only a small differences in the number of sprays it took. I couldn’t measure the masks by the amount they let through.

This is not scientific. It’s more about providing context and information. You’ve likely already made your choice, this helps understand the choice.

The masks

I tested a variety of masks. A sample of each type is shown in the picture. The testing hood and sprayer is at the top of the picture.

I’m going to describe them clockwise, starting with the one labeled “For Compliance”:

• the typical cloth mask that most people wear, for compliance and fashion rather than for effectiveness (I got this custom made because I’m a troll)

• surgical mask

• typical KN95/KF94/N95 disposable mask, with bands that go around the ear

• real NIOSH N95 disposable mask (3M Aura N95 based on this thread), with bands that go behind the head

• elastomeric respirator, quarter-mask (FloMask Pro based on this thread)

• elastomeric respirator, half-mask

• elastomeric respirator, full-mask

• a MicroClimate AIR2 — which isn’t a medical thing at all, but since I’ve gone this far, yolo…

The word “elastomeric” means a soft plastic seal that goes around the edge of the plastic mask/respirator. They aren’t disposable but take disposable filters. The AIR2 cost $300, but the rest of the masks cost in the $30 price range (either for a box of disposables, or a plastic mask with some disposable filters).

I tried more masks than pictured here. The above list is just the categories you have to choose from. Once you pick a category, you’ll have to find one the fits (no leaks) and is comfortable for many hours of wear. Different people will find different models fit better.

For efficacy, the minimum is really the NIOSH N95 (or equivalent). This means something that filters small particles but also bands that go around the head.

People are really confused by this. The think they have N95 masks, but they don’t. If it loops around the ears, it isn’t. Almost everyone is wearing masks with bands around the ears, and almost nobody is wearing masks with bands around the head, so they don’t even know what I’m talking about. It looks something like this:

Some disposable masks are behind the head, all the plastic masks are that way, too.

The results

The results were rather binary.

• The first two masks (the compliance cloth mask and surgical mask) were complete failures. One spray and I immediately tasted the nasty bitter flavor. I could tell no difference between these masks and no mask.

• My KN95 (around the ears) mask actually worked well, but primary due to the shape of my head, most wouldn’t perform this well.

• For the rest of the masks (around the head), if they had a seal problem, I could detect that within a few sprays of the atomizer.

• For the ones with no seal problem, no amount of spraying resulting in tasting the bitter compound (I did at least 30 for each one, or 50 if I was trying real hard to break it). I tried real hard. If it’s N95 filter material, and there’s no gaps, you are good to go.

• I did an extended test, smiling and scrunching my face. Most all the masks failed this test. I don’t know if the problem is my face or whether it’s a common issue for all masks. Just try to keep smiles to a minimum, I suppose.

I notice something wrong with these results. An N95 means blocking 95% of particles, not 100%. That means I should taste in 20 sprays what the cloth mask allowed through in 1 spray. I tasted nothing, no matter how many sprays I did.

I even ripped off the hood and put the atomizer directly against a couple of the masks and sprayed 20 times into the N95 material and I could still detect nothing. I sucked hard trying to pull that stuff through the masks and it didn’t work!

For my tests, therefore, the N95 materials were all 100% effective (as long as no gaps in the seal). I don’t know what this means, because they shouldn’t be 100% effective.

Maybe it’s due to particle size. The covid particles can be as small as 0.06 microns, the N95 is rated for 0.3 microns, and my test particles range in size from 0.3 to 5.0 microns. Since it’s electrostatic charge doing the work, for all these particle sizes, it might not matter. Or maybe it does.

The consequence of this test is that if it’s not some sort of N95/HEPA material, it’s worthless (well, worth less — not completely ineffective, but so far down the effectiveness scale that it doesn’t matter). The simpler masks were indistinguishable from no mask at all, and the N95/HEPA masks (when sealed) where indistinguishable from perfect.

Again, I stress this is not scientific. Other (better) tests show a range of things. This link by better scientists comes to much the same conclusion: anything less than N95 sucks. Thus, I’m not too far off.

So a NIOSH N95 (around-the-head) is the lower limit. As described above, these can be:

• disposable

• elastomeric quarter-mask

• elastomeric half-mask

• elastomeric full-mask

For efficacy, my test doesn’t show any differences among them. Some elastomeric masks have “P100” filters, in theory filtering at 100% instead of 95% efficiency.

When I put on the elastomeric masks, breathing seems harder. But I don’t think this is actually true, since the surface area of the disposable filters is actually greater than disposable masks.

So you can pick anything here that #1 gives a seal without gaps and #2 is comfortable.

Since you aren’t going to spend $350 on fit test kits for the home, you can’t test the seal very well.

But I found it pretty obvious which masks had a good seal and which didn’t. When you do tests, like moving your head around and talking, poke at the seals with your fingers to see any gaps. I also find that simply exhaling works — if things billow outward, it’s a good sign there are no gaps.

The FloMask quarter-mask made me worried, because the bottom kept sliding around while talking, so I thought there might be problems. But the fit testing showed it still worked.

For peer pressure reasons (so that people don’t look at you funny), you’ll probably want a disposable mask like the 3M Aura N95 or an elastomeric quarter-mask (like the FloMask). The half-mask looks like some creepy WW I gas mask, and the full-mask looks like a Contagion or Outbreak movie.

Finally, let’s talk about that MicroClimate AIR2. It’s not a medical thing and comes with HEPA filters instead of N95, though as far as I can tell, they are roughly the same sort of thing (almost all 0.3 micron particles). It weigh 2 pounds (including battery) and has a little fan sucking air in through one filter and out the other. This constant airflow means breathing is more comfortable, and the face plate doesn’t fog up.

It’s clearly the winner in all sorts of fit tests, because it goes around the neck and is the easiest to breath through. However, it had one fatal flaw for me: when my forehead itched, I couldn’t scratch. The fabric on the side is stretchy enough for most scratches but I couldn’t figure out how to scratch my bald forehead.

Conclusion (real life edition)

If you don’t care about efficacy, then of course you can skip all this.

Otherwise, the three things:

• get at minimum a NIOSH N95 — something with bands around-the-head rather than around-the-ear

• really really make sure it fits without gaps, do your best

• you’ll have to try multiple products until you find one that fits your face comfortably without gaps

I recommend you start with disposable masks, like 3M Aura N95. Look for anything NIOSH N95 certified on Amazon.

Note that when you go on Amazon and purchase them, you may end up in the woodworking section rather than the medical section. As far as I can tell, they are all the same for our purposes. Some of the medical ones also protect you from hazards like blood spraying into your mouth during surgery (like this slightly different model).

If you can’t find workable disposable masks, then move up to the elastomeric masks. They are also pretty cheap, in the $30 range. They are weird looking, and I struggle with the way they interfere with eyesight, but I find some of them comfortable.

The elostomeric quarter-masks are pretty comfortable and socially acceptable, at least, won’t cause small children to flee. The only one I looked at was the FloMask Pro. It also has the option for P100 filters instead of N95. All such quarter-masks are going to move around on your chin, which I found annoying — but they appear to still keep a seal.

Conclusion (DEFCON edition)

In addition to the above notes:

• Nobody likes unsolicited mask advice. I mention this because most everyone at DEFCON is going to be wearing the sorts of masks this blogpost says are ineffective (well, dramatically less effective). I’m certainly going to silently judge them :-), but in all seriousness, it’s okay that people disagree, and it’s a struggle to find comfortable fits.

• On the other hand, do bring extra disposable masks, for your friends (or strangers) that are struggling to find the exact model with a good comfortable fit. If they ask.

• DEFCON is a very hands-on community, from lockpicking to packet-sniffing to soldering. So maybe splurge and buy one of those $350 test kits and invite people ‘round to test their masks.

• Most importantly, don’t be embarrassed wearing one of those elastomeric respirators that look like gas masks. This is DEFCON, cosplay the shit out of them!!!

FAQ - some answers to questions

Q: Foldable vs cup vs that 3m halfway thing?

If it has straps that go around the head (rather than around the ear), it doesn’t matter. All the matters if it’s N95 material and has a seal against your face without gaps, especially when you are talking.

Q: Is a gas mask with appropriate filter better?

Actual “gas” masks filter gases. You’d need to look at their “particle” rating, like “P95” for blocking 95% of small particles.

You are probable thinking of the elastomeric respirators anyway (pictured above), some of which come with P100 filters instead of N95 filters. Technically, a P100 filter will be better, but overwhelmingly the most important issue is to have a seal against the face, so I wouldn’t worry about it.

Q: What’s up with that space helmet thing in the picture? Can you hold a lecture while wearing it and have the audience hear you?

I don’t really know what it’s supposed to be for. I just added it to my test because I always take that one extra step. It’s a MicroClimate AIR2. The “fog resistance” really works, which is surprising, the face plate never fogs up because of the fan exchanging the air. The air exchange makes this the easiest mask for breathing.

If I could figure out to scratch my forehead when it itches, I’d like to try it out on airplanes. It seems kinda perfect for situations like that.

The vents are angled so you can have a conversation, but I don’t think a lecture would work. You could try AirPods, speaking out to speakers, but I’m not sure if the fan noise would get in your way.

Q: N95 or KF94?

Any of the small particle filters work with grades of around 95%.

What matters is the fit around your head so there are no gaps. That probably rules out KF94 with straps around-the-ears. You really want around-the-head. That’s why we stress NIOSH N95 — the NIOSH certification includes mandating around-the-head.

Q: How well can you be heard?

I didn’t test masks for that. I talked into the mask, to test the seal, but I didn’t measure how muffled it was.

Q: Which will make me look like a cyberpunk badass?

The elastomeric half-mask looks most like a gas mask, and it the one of the DEFCON picture. You can probably dress it up a bit more for extra punk. As long as there’s no gaps, it’s as good as anything else.

Q: Which one is tight enough on exhale that it won’t fog up my damn glasses?

If it’s fogging your glasses, it’s got a gap, and needs to be thrown away. The elastomeric ones seem to have the best fit around the nose.

Q: How can be people assure that what they are getting is legit, and one of the many fake scams on Amazon?

I don’t know. I suspect moving up to quality masks (NIOSH certified printed on the mask) is a good start. Also, “Sold by Amazon” or “Sold by <manuf>” matching the manufacturer’s name printed on the mask is probably also safe.

Q: Is the 3m N95 versus P 100 cartridge difference enough to be warrant upgrading?

In theory, it should stop a lot more, but I couldn’t see it in my tests. The tradeoffs are that it’s harder to breath through, though in my brief test, it didn’t really seem harder. I’d certainly pick it if I could just on general principles that going from 5% to near 0% particles is a good idea.

Q: How much of a difference on fitment does the W clip versus the V clip make? See standard 3M n95 verse cool flow.

I have no clue, sorry, I didn’t get that far in details. I suspect that each type of clip will make differences for different people.

Q: Does the fabric matter more than how it’s worn?

In my tests:

• bad fabric (not N95) was instantly detected in the first puff of the atomizer

• bad fit took around 3 puffs of the atomizer

But I suppose that depends upon the size of the gaps.

Q: Tell me about Bane. Why does he wear the mask?

He had the problem fixed years ago and just wears the mask because he’s emo.

Q: What's the comfort level of the best performing one? What's the comfort level of the least performing one? Should we compromise on performance for comfort? And if so, how much?

In my test, “performance” is fairly binary. I either tasted none of the Bitrex after 50 puffs, or I tasted it after a puff or two. there is a ton of selection out there for finding one that fits. Of course, getting them to try on is hard without buying one of each.

If it’s bad performing, it’s slightly better than nothing at all. That’s what I reserve my custom “For Compliance” mask for: situations where I don’t think it’s a problem and they make me wear a mask — any mask — anyway.

Q: Reasonable thoughts about reusability of masks

I have no clue. I googled and could find no answer. The best answer is “depends on the environment” when gases or dust make them smelly or hard to breath through.

Q: I was always curious about the effect of adding the pm2.5 carbon filters to masks

Makes no difference for particles, only odors (gases).

My custom “For Compliance” mask in the picture above comes with a pm2.5 insert. It was like not mask at all.

Q: Does wearing a bird mask along with an N95 give you any extra protection?

Maybe from monkey pox, because every will want to stay away from you.