[last updated May 2nd, 2024]

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What’s a respirator?

Short version: it’s like a mask, but better. *Much* better.

Let’s put the headline news up front: if you maintain an airtight seal at all times, a P100 respirator blocks 99.97% of incoming viral particles. [source]

Yeah. 99.97%. That’s a *lot*.

(Specifically, we are going to be talking about what’s called “elastomeric” respirators. These have a base unit made of plastic and silicone, with attachment points on the cheeks for swappable filters.)

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What are your credentials? / Why did you write this? / Why is this important to you?

I’m an immune-disordered person who’s found it absolutely life-changing to have a high-grade prosthetic immune system, and I want to share that joy with others.

My reasons aren’t everyone’s, though. Maybe you have diabetes, or permanent throat damage from acid reflux, or one (or more) of the many other conditions that can make respiratory illnesses more dangerous; maybe you don’t personally, but you have close friends or family who do and you want to be a firebreak for them; hell, maybe you have a phobia, I won’t judge. Your lungs are your own, and you get to decide what goes in them.

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99.97%?! What’s the catch?! There’s gotta be a catch, right?

A few catches, but generally nothing dealbreaking.

The filtered air is very dry if you’re using nuisance-vapour filters (more on that below) and very humid if you’re using particle-only filters. For a while there, I was working 4 – 5 hour shifts for 2 – 3 straight days a week with a nuisance-vapour respirator and no water breaks, and that’s *doable* but dehydrating.

The 99.97% figure is for *incoming* air. Most models of elastomeric respirator do not, by default, filter outgoing air. However, there are several mitigating factors:

• Since you can’t spread a disease you don’t catch, protecting yourself *is* protecting others.
• Some newer respirator models, such as the MSA Advantage 900, have filtered outflow, though I have not had a chance to try any of these myself (edit: see the postscript for more info).
• Other models, such as the 3M 7502 that I use, have a right angle in the valve. The original point of this is to direct your breath downward so that it doesn’t fog up your glasses (and it *is* very helpful for that!), but the right angle also catches some of the droplets. To improve it further, I tape a layer of cloth over the valve. (Two layers of cloth causes too much breathing resistance to be feasible; I’ve heard of people clipping out pieces of N95 to use for this, but found it to be likewise too high-resistance.)

Elastomerics generally muffle your voice somewhat more than masks do: you’ll have to speak louder and probably be more careful with enunciation than usual, and talking on the phone will be very difficult. Some of the newer models (such as the abovementioned Advantage 900) have speech diaphragms to help with this: you can hear what that sounds like here.

They cost more up-front (about USD$30 for a base unit and USD$11 per pair of filters, depending on what kind of filter you buy), but they last for such a long time (more on that later) that in the long run it’s actually very economical.

Some people think they look funny, though people in 2019 would have told you masks looked funny too.

(If any of these *are* dealbreakers for you–for example, if you’re a call-centre worker–you might want to look into disposable N95s that have integrated silicone seals. I haven’t tried them myself, but I’ve heard some intriguing things about SoftSeal.

If you’re going for a job interview or similar and desperately need to not look the least bit weird, I recommend Good Manner KF94s. I *have* tried those: they run rather large, but the “kid” size fits me fairly well and is good as masks go. I keep a couple in my bag as a backup: the flatpacking is handy for this.

If you can afford to look *very slightly* weird, tape around the edges of the KF94 with paper medical tape to prevent leaks. White tape on a white mask can blend in somewhat.)

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So why aren’t more people using respirators already?

Often it’s because people don’t know about them. Cloth masks were supposed to be a stopgap measure until we had a chance to manufacture more of the various higher-quality forms of respiratory protection, but a lot of people stuck with what was first done and didn’t hear about news of changing availability. Respirators do *sometimes* go out of stock still, but they’re very often available now.

Also, the kind of respirators we’re discussing in this post are aimed at construction workers, which means people looking for “medical” masks tend to overlook them. But a particle is a particle, and there’s no reason you can’t use construction respirators against germs. In fact, in some ways they work even *better* against germs than they do against construction fumes.

(Things *have* improved somewhat since I wrote the first edition of this guide: I’ve encountered a couple of people wearing elastomerics in the wild, and I’ve been seeing more pro-elastomeric articles lately (including in the New York Times).)

I first wrote this guide before COVID-19 vaccines were widely available, but–especially in this vaccinated age–many people find that their cost-benefit analyses don’t come out in favour of masking at all: they’re not in any high-risk categories, their close contacts aren’t in any high-risk categories, and they don’t find their remaining amount of danger to be worth concern. If that’s you, that’s fine, but consider keeping an elastomeric base unit and a couple pairs of filters in the back of your closet as insurance for the *next* time a novel pandemic arises: there were many before COVID-19, and it’s a safe bet there will be many after.

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What do I need to know about how to wear them?

First, check the fit. Take off your glasses if you have them, then put the base unit on and adjust the straps until the seal is airtight without being painful. You won’t be able to get an airtight seal if there’s facial hair in the way: if you value leaving your facial hair unshaved, consider using a thattha.

To confirm that the seal is airtight, there are two methods.

• If the filters are *not* attached (or if you’re using filters that are designed to allow inflow tests: more on this later): cover the attachment points with your palms and try to breathe *in*. If you can’t, the seal is airtight. (Except for the attachment points themselves, of course: *those* are big gaping holes in your seal if they don’t have filters on them. But we’ll be fixing that soon.)
• If the filters *are* attached: cover the valve at the bottom with your palm and try to breathe *out*. If you can’t, the seal is airtight.

(You’ll want to confirm the seal every time you put the respirator on.)

Next, take a pair of filters and put them onto the attachment points. (This is much easier to do if you’re not wearing the respirator while you’re doing it.) Attachment methods vary between models, but for the 3M “bayonet” respirators we’ll be primarily discussing here (as they’re what I have experience with), they screw into place. Be sure to screw them on very tightly, otherwise they might fall off. (I didn’t screw them on tightly enough my first time, and it was pretty scary when one of them fell off in the middle of a crowded restaurant. But now that I’ve gotten them on correctly, they stay put.)

Now you can wear it. If you have glasses, take them off first, then gently rest them on top of the respirator’s nose once you’ve put it on. Check the seal as above to make sure it’s airtight.

After every few hours’ worth of wear, wipe down the silicone (the part that sticks to your face and forms the seal) with some mild cleaning solution to keep the skin oils from building up. You can also wipe down the outside if you are concerned about fomites, but note that of the two styles of filter (more on that later) you can *only* wipe down the plastic “box” cartridges, *not* the pink “pancake” cloth circles. Here is the official manufacturer’s guide on cleaning these respirators: note that “quat” is janitorial jargon for the type of cleaning solution that Lysol wipes are dipped in.

(Bonus tip: if you’re having trouble sourcing disinfectant wipes, look for bottles of “quaternary ammonium” *next* to the barren disinfectant-wipe section at the grocery store, put it in a spray bottle diluted to the level stated on the bottle instructions, then heavily spritz a paper towel with it. Voila, a disinfectant wipe!)

According to the CDC, the filters last somewhere between a month and a year depending on how much you need to conserve resources and how well you can avoid getting them wet or dirty. The main limiting factor on longevity is that the filters get clogged with fumes and dust from the construction work: if you’re not *doing* construction work or similar fume-heavy activities, they can keep going for ages. If you can still breathe through it and the filter hasn’t been wet, you’re good. (I usually replace mine every 4 – 6 months, but I keep my old filters in reserve in case of wildfires.)

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What’s this about different kinds of filters?

I’ve used three different types of 3M bayonet filters over the years, and they each have their pros and cons.

2097: “pancake”-style filters, with a nuisance-vapour layer.

• Pros: The filtration on these is so good that they induce complete anosmia while you’re wearing them, which (if you had a sense of smell to start with) makes them deeply reassuring right down to your subconscious: you can viscerally *sense* them working. (Note that a given pair will wear out somewhat after 2 – 4 months of use: after that you start being able to smell gases, though not particles.) The air isn’t muggy like particle-only filters can be. They’re cheap, at about $12 a pair.
• Cons: No water resistance, so you’ll have to be very careful to avoid rain and other splashes: pocket umbrellas help, but only so far. (I work at a restaurant where my duties include rinsing dishes with a dishwashing sprayer, and it was a pain.) They filter out ambient water vapour while the nuisance-vapour layer is still working, making the air very dry. They’re pink, which some people feel strongly about. Anosmia has its downsides.

7093: “box”-style filters, particle-only.

• Pros: They’re water-resistant: they’ll still be ruined if submerged, but they’re designed to let you take decontamination showers with them on, which makes them very good for rain. You can squeeze them shut to test your seal against incoming air. They muffle your voice slightly less than pancake filters do (though it’s still muffled overall). If you want to retain a sense of smell, these are great for that: they let through all sorts of scents, while still being just as effective against germs. They don’t filter out ambient water vapour. They’re purple and grey, not pink.
• Cons: Not subconsciously reassuring at all: I bailed on them after two days because I was tired of having to constantly override the visceral sense that they weren’t working. (I now keep them in reserve in case I encounter a situation where I actually *want* to have a sense of smell.) Ambient water vapour added to the water vapour in your breath (not all of which leaves through the valve) can make the air feel muggy. A bit more expensive than 2097s, about $16/pair.

7093C: box-style filters with nuisance-vapour filtration (and also hydrogen-fluoride filtration, but that’s not relevant here).

• Pros: Enough scent-blocking to make you aware that they’re doing stuff. Like the 7093s, they’re water-resistant, allow for inflow testing, and have noticeably less muffling.
• Cons: Not *complete* anosmia, although you may consider this a pro. While they’re mostly yellow and grey, there is some pink. Expensive, at about $30/pair.

I personally wear 7093Cs these days because I wanted both water-resistance and scent-blocking and decided I was willing to pay an extra ~$35/year for them, but the others each have their place.

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Where can I get them?

Depends on where you live, but there are usually three general categories: Amazon, hardware stores, and industrial-supply stores.

Amazon has a reputation for mixing together instances of the same item from different sellers: this means that if *any* seller is selling counterfeit (and counterfeit 3M filters are known to happen), *every* buyer gets a crapshoot. Exercise caution if buying from Amazon, and consider preferring 2097 filters because the total scent-blocking means it should be extremely obvious if the filters aren’t as good as they should be.

Hardware stores don’t always have the best selection, but they can work well.

If you ask 3M where to buy their products, they will direct you to industrial-supply stores. Many of these sell only in bulk, but some offer smaller packages, plus you may be able to split, say, a 12-pack with some friends. I currently buy my filters from Canadian industrial-supply stores SPI Health and Safety and International Safety (depending on who’s got them cheaper at the moment), which are both stores that 3M links to.

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Anything else I should know?

While we’ve focused on their benefits against germs here, elastomerics are also great against smoke: I’ve met Californians who kept them on hand *primarily* for wildfire purposes.

They’re usually overkill against pollen, but if you’re wearing one anyway it will keep hayfever at bay, and if you’re spending extended periods of time exposed to pollen you’re very sensitive to, a P100 can give you the extra edge you need when lesser masks aren’t quite enough.

If you’re at especially high risk (whether a particularly fragile body, a particularly dangerous situation, or some of each) and find that your cost-benefit analyses come out in favour of “full-face” respirators that cover the eyes (as opposed to the “half-face” respirators we’ve been talking about, that cover only the nose and mouth), consider instead combining a half-face respirator with goggles for more flexibility. I keep a pair of goggles on hand (these ones fit over the top of glasses) in case of having to treat sick people or go out in a plume of wildfire smoke: more mundanely, they’re also handy for preventing onion tears.

You can drink things by lifting the bottom of the respirator up, sticking a straw through the gap, and putting the respirator back down when you’re done taking a sip. (I actually find this easier than drinking with a mask on, especially since I usually have to tape my masks shut.) I’ve started keeping a metal straw in my bag for this.

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Getting a respirator has been amazing for me, and I hope it can help you too. If you found this useful or know someone who would, please let people know.

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Thanks to The Prepared, nuclearspaceheater, and andmaybegayer for their inspiration and information. I couldn’t have done this without them.

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Postscript, 2024-05-02:

Last year, I bought an MSA Advantage 900.

Upshot: if I were doing it again now that the 3M Secure Click speech-diaphragm respirator is available in Canada, I’d probably go for that instead. The Advantage 900 is a valuable part of my toolkit, but it has some pretty strong downsides. I would not recommend it to most people, and it should definitely never be the only respirator you own.

That being said, I think you should consider having some speech-diaphragm respirator on hand so that you can talk to people during the next pandemic without it being a pain. Even if you’re normally fine with just using disposable N95s for speech-heavy usecases, it is much, much more feasible to have a year’s worth of elastomeric-respirator filters on hand than it is to have a year’s worth of N95s on hand.

In 2020, elastomerics were entirely sold out by late January. If you learned about the threat of COVID-19 from Siderea’s locally-famous post “So Maybe We’re Having a Pandemic” (January 30th, 2020), you were both relatively early to preparing and already too late.

So, then, if you want to have a speech-diaphragm respirator during pandemics, you should aim to get one before the next pandemic starts. There is no reason to think that the supply chains will be there for you when you need it, and every reason not to think so.

As for a more detailed review of the MSA Advantage 900:

Pros:

• The speech diaphragm really is incredible. As I said in the initial post linked above, “I can explain complicated things to customers now! I can attend social gatherings in a P100!”
• I said in my initial post about it that the light blue “looks a bit nicer”, but I was seriously underestimating how much difference looking a bit nicer makes. I’ve gotten maybe one or two instances of street harassment in seven months, whereas it was happening once or twice a month with the 7502 (more often the less common masking-at-all became).
• I got used to the particle-only filtration a lot faster than I was expecting.
• It doesn’t have a valve: the 99.97% filtration also applies to your own breath on its way out and not just outside air on its way in. This makes it good for circumstances where you’re not very confident you’re not sick (such as when you’ve only just left quarantine), or when you know you’re sick but you still have to interact with people to receive medical care etc.

Cons:

• It’s expensive. I paid CAD$127 (about 94 USD) for one base unit + one pair of water-resistant filters + shipping.
• It’s much less comfortable than the 3M 7502. Less so if I put it very high up on my nose, but it still leaves a welt on my nose-bridge.
• The seal-testing system doesn’t work very well.
• The combined head/neck strap system makes it hard to repeatedly lift and lower the mask without careful repositioning. The 3M 7502 is, therefore, much easier to eat through.
• The filters for this respirator model don’t have an option to filter gases. This makes them less than ideal for smoke (though still pretty helpful, since most of the badness of smoke is particulate), and generally narrows the circumstances under which they’re useful.
• While the lack of valve can be beneficial, it also presents serious problems. Particle-only filter + valveless base unit = lots of water buildup. Like, there is a substantial puddle in the bottom of my mask after a couple hours. After about 4 hours, I can feel it spraying on me when I talk. I have to be careful not to lie on my side, lest I tip the puddle into a filter and cause it water damage. It’s so humid that, if my body is already feeling fragile for other reasons (past reasons have included “significant-but-not-normally-enough-on-its-own-to-cause-nasal-symptoms level of pollen exposure” and “prodromal COVID-19†”), it can actually fuck up my sinuses pretty badly. Carry pseudoephedrine in your bag, if you’re going to use this respirator on a regular basis and live in a place where pseudoephedrine is legal.

†I held out for two weeks with a COVID-positive housemate! …he was contagious for three weeks.