The Compass DeRose Guide to Gas masks

This page was written by Steven J. DeRose in early 2003, and was last updated on 2003-04-12.

This page discusses the different kinds of gas masks, from mil-spec NBC protection on down to what you can throw together in a minute from common materials. I believe gas masks are a worthwhile investment, so long as you understand their limitations (especially that for civilians their best purpose is to buy time to escape), take the time to learn to use them properly, and try to keep them near enough to be useful (like, say, in your car).

(under construction; and I am *not* an expert on this)

The types of masks discussed below are organized from best to worst. Remember that masks are not just useful in terrorist attacks -- if you have a road or a train track within a few miles, you could encounter accidental chemical spills of almost anything.

You can also use a full-fledged NBC mask for workshop protection. They'll certainly do a fine job on non-lethal dusts, and they'll give you eye and face protection much better than hardware-store goggles. They'll also steam up a lot less. And using them this way will keep you in practice. Weigh that against the added wear and tear on the mask. Then again, since the probability you'll use your mask for real is pretty low, getting some use out of it (and saving the cost of non-lethal irritant masks) could be a plus.

Positive-pressure breathing apparatus

This involves air tanks rather than filters. The chance you'll have this around when you need it is slim: too expensive, heavy, requires training, and doesn't last long. But, as I say in many places, if you're stuck you use whatever you have. The only likely way you'll have an item in this category is if you're an avid scuba diver, or a medical professional. In either case, I assume you know how to use it better than I do.

Note: I can't help but picture the James Bond scene where he uses air from the tires of his sunken car, to breathe until the killers watching are certain he must have drowned. I once figured out how much time you could get that way, and the scene wasn't unreasonable; but wheels aren't portable, and they don't buy you very long at all, so don't bother trying this one at home.

Real NBC gas masks

Some basic rules about gas masks, before you go out and buy one:

• Make sure it uses 40mm NATO standard filters. Anything else is probably way obsolete, and you won't find in-date filters for it anyway.
• Make sure you can change filters without leakage in a hazardous place (even though you should be long gone from the area before it's time to change the filter).
• Avoid surplus masks or filters. You don't want to worry if there's a tiny crack in the faceplate seal, or if the gaskets have harderened a little and don't quite seal, or the exhaust valve sticks so you end up getting air in through it, or whatever. If you're going to buy a mask at all, there's no point in buying a cheap one.
• Most adult masks don't fit kids, though smaller sizes are available if you look around. Smaller kids may not be able to manage the continuous extra effort needed to breathe, and may not be able to remember that they mustn't take the mask off even when it gets uncomfortable. Special infant and small child versions exist, with big hoods and battery-powered fans to do the work.
• Make sure you over-learn how to put the mask on -- practice so that you can do it even with your eyes closed, and still get the fit and seal right. Be able to get the mask on in 10 seconds flat (and hold your breath while you do it!). If and when you really need to use it, you'll be stressed out, in a hurry, and in tough conditions. Try to get a friend who's been trained (military, fire/rescue workers, etc.) to go over it with you.
• Know how to test for fit and leaks, and do it every time you put the mask on, even for practice. Be especially careful if you wear glasses or have a beard -- my mask leaks badly if I don't take my glasses off. If you need your glasses, figure out a way to keep them on without the side-pieces (which are generally what make the mask leak). At least, be ready to break off the side pieces and tape your glasses to your face.
• Have extra NBC cartridges, and make sure they're in date. Don't unseal them until you need to use them (I presume they would start neutralizing whatever pollution is drifting around, and by the time you need them they might be useless). If you have to practice get an extra cartridge and use the gas mask when you'd use a dust mask around the house to get used to it. Seal the cartridge in a ziploc bag when not in use; it might help it last longer.
• Stay relaxed when wearing a mask; you'll use way less air, so the filter will last way longer.

A decent mask will probably cost around $100. Filters aren't cheap either. As with other equipment (or stocks for that matter), if you want one, buy it before it becomes obvious that you should, or you won't be able to get one. If you're buying for a group (like your family), get all the same kind.

Most filters claim to last 8 hours -- reality depends on how much of what stuff they have to neutralize. Some chemicals like diphosgene use up masks' filtering capacity far faster than others. How many you want is anybody's guess.

Semi-real ("Non-lethal environment") masks

During "duct tape week" I saw a woman at a hardware store buying several painter-style masks -- they're designed to keep out paint fumes, asbestos, fiberglass dust, and so on. Don't think for a moment these are anything like as good as a real military-style gas mask. But they can protect against some things. Depending on what comes at you, and how much, they could save your life... or not.

In this regard, remember that chemical leaks from train or truck crashes happen much more frequently than terrorist chemical attacks. Many such chemicals can be neutralized by these masks, giving you time to escape.

Big hardware stores carry these, and they typically cost $20-30. Replacement cartridges cost almost as much. They come in many varieties. Every company seems to have incompatible filters, and there are many filter types for particular uses. MSA has a good brand reputation.

Allergy Be Gone sells a variety of cartridges for a "6000 Series" mask, that protect against various things: organic vapors, acid gasses, Ammonia Methylamine, Formaldehyde, Mercury Vapor, Chlorine.

These masks do not cover the whole face, just the nose and mouth, which means they will not help you enough against eye irritants (of which there are many). If you get them, practice putting them on, and know how to test the seal (basically cover the air intake and then try breathing in -- if you get anything, it's not sealed. Also, just to remind yourself that they aren't real, try generating some nasty smoke, like from a campfire, or from cutting wood with a dull power saw blade. I discovered by accident that these masks do nothing for that.

How masks work

A mask has to make a tight fit all around, so when you breath in you only get air that comes through the filter. They generally have a full-face plastic front, a soft rubber edge, and 5 or 6 straps to hold them on. There are separate one-way valves to let out exhaled air. The filter is a separate piece, and may have several parts:

• Plain old filter paper to catch dust, like a car air filter only better.
• Activated charcoal is usually in there, because it absorbs a lot of different chemicals. It's used in water filters, air cleaners, and so on.
• Some masks have special chemicals intended to react with particular agents. For example, I'd bet the "acid vapor" hardware-store masks have some base in there to neutralize the acid. But since you'll seldom know what you'll be facing ahead of time, why bother (unless you live near a specific chemical hazard)?

Makeshift or expedient "masks"

In emergency preparedness circles, stuff you throw together at the last minute from whatever you have available, is called "expedient" protection. In a pinch, get anything you can between you and the contaminated air. Even a coffee filter, gauze pads, or some cloth will catch some portion of dust. If the dust is dangerous, breathing less of it is better.

• An extra NBC filter could be used as an expedient mask simply by sticking the threaded connector in your mouth and taping, clipping, plugging, or holding your nose shut. Probably a useful hack if you've got one mask, one extra filter, and one maskless friend; or if your level of concern and budget combine to make this the best you can afford.
• "Tuberculosis" masks physicians wear when dealing with TB patients -- a Nurse Practitioner friend tells me these have much better filtering than typical surgical masks. GIven recent cases of lethal pneumonias getting onto airplanes, this might be a good thing to wear on long flights.
• Surgical masks -- I think these are slightly better than dust masks, but not much better. Should stop large bacteria and dusts; probably won't do much for viruses, or anything for chemicals. Medical masks are available many places, including the Medical Supply Company.
• Nuisance dust masks (the cheap paper ones from hardware stores) -- will take out some dust (which could inlcude some radioactive dusts). This is certainly is better than nothing. Don't think of these as protection, though.
• Wet cloth over nose and mouth -- a few poisons dissolve in water. Don't count on this for much, but if it's all you've got, you might as well try it. I've heard this works fairly well against chlorine.

With all the "masks" in this section, adding a pair of swimming goggles is a good idea. Some toxins can be absorbed through the eyes easier than through the skin; and closing off your nose (heck, use a clothespin if you have to) is a lot safer than trying to remember never to breath through it. But none of these will do much; in a pinch they may be better than nothing; or they may just be equal to nothing, depending on the situation. Get a real mask well ahead of time, and keep it where you can get to it fast a large percentage of the time.

Back to home page of Steve DeRose or The Bible Technologies Group. or The Bible Technologies Group Working Groups. Or, contact me via email (fix the punctuation).