Personal Planning
Considering a Gas Mask? Be Sure It's a Good Fit

I am living proof that gas masks work. I strapped one on recently in the third-floor conference room of Geomet, a Germantown-based "health and personal safety" company. And then I chopped up a raw onion with a paring knife.

In the face of the bulb's chemical onslaught, I didn't shed a single tear. Nor did I detect a whiff of the onion's distinctive tang. If terrorists attack with diced onions, a gas mask will protect you.

Of course, VO -- Vidalia onion -- isn't what people are worried about these days. VX is. And GB, HD and other frightening combinations of the alphabet. Because of that fear, some consumers are curious about gas masks, or what are more broadly known as respirators.

The federal government does not endorse the idea of civilians donning gas masks. The answer to the very first question on the Web site's FAQ section states: "The use of gas masks and hoods by the public during a chemical threat is not recommended due to legitimate safety concerns."

Those safety concerns are not trivial. Use a gas mask incorrectly and you can be killed by your own fumblings long before al Qaeda has a chance to get you.

This is not to say that the Department of Homeland Security is totally anti-mask. The Web site does mention that "filter masks" can help keep out germs from a biological attack or debris from an explosion, and it says that "something over your nose and mouth in an emergency is better than nothing."

The Filter Mask

That "something" starts with cheap, disposable filter masks found at hardware and paint supply stores. These respirators are rated by the size of particle they protect against and the durability of the filter material. A mask rated 95 means it will stop 95 percent of particles that are 0.3 microns in diameter or larger. The other particle size ratings are 99 (filters out 99 percent of the 0.3-micron particles) and 100 (filters out 99.97 percent, an efficiency comparable to a HEPA filter).

The most common mask is an N95. The N means that the material it is made of is not oil-resistant. A P rating means it is oilproof; an R rating means it is oilproof but can be used a maximum of eight hours.

The anthrax spores in the letter mailed to then-Senate Majority Leader Thomas A. Daschle (D-S.D.) were 1.5 to 3 microns in diameter, so an N95 can safeguard against the disease. (Smallpox, on the other hand, is smaller than 0.3 microns.) In his book "When Every Moment Counts," Senate Majority Leader Bill Frist (R-Tenn.) recommends that N95 masks be included in every disaster supply kit. They start at about $1.

If you decide to get an N95 mask, be sure it has a moldable metal noseband and crimp it when you use the mask. It will help create a better seal.

Some masks have plastic valves to release your expelled breath so the respirator doesn't get too hot and your glasses don't fog.

Some N95 masks are called "harmful dust respirators." Stay away from what are called "comfort" respirators, masks designed to wear while you're raking leaves or sweeping the floor. (A crude rule of thumb: A mask that is held on by a single elastic strap is less likely to be an N95 than one that has two straps.)

And if you're stuck without a mask, you can follow the advice on and breathe through fabric, such as a folded-up cotton T-shirt or diaper.

Half Masks

Next up in price are what are known as elastomeric respirators. These are typically half masks that cover the nose and mouth and can be fitted with different filters. A P100 or HEPA filter strains out particles, including the sort of radiological particles scattered by a "dirty" bomb. Various types of charcoal filters can neutralize small amounts of certain industrial chemicals, such as ammonia and pesticides.

Prices start at about $10. They won't stop the nastier nerve gases, but if you're several miles from an overturned chlorine tanker and a cloud is coming your way, they do afford some protection. Since the mask doesn't cover the eyes or rest of the skin, you can still get a dose of chemicals that way, but they do protect the lungs, the primary route of attack with gas.

Manufacturers of N95 masks and half masks are quick to point out that their products were not designed with chemical, biological or radiological attacks in mind.

Masks, Escape Hoods

Most gas-mask manufacturers and retailers agree with Homeland Security Secretary Tom Ridge that gas masks don't belong in the hands of the public. Experts say they are too difficult for civilians to fit and use properly. Most can't be worn with glasses or by men with beards.

The alternative is the escape hood -- basically a plastic bag with a rubber neck dam and a particle/chemical filter. Unlike a gas mask, which requires that straps be carefully adjusted so there's a leakproof seal between face and mask, an escape hood pretty much seals automatically around the user's neck after it's pulled on.

ILC Dover, the company that makes spacesuits for NASA, has introduced a civilian escape hood. Called the SCape, it's packed in a container about as long and a little wider than a box of tissues. It costs $199.

The SCape is what's called a "positive pressure" unit. A tiny motor is activated when the hood is pulled from its box. The motor sucks air through a set of filters and into the hood.

Other civilian models include the Gas Mask Hood by Mine Safety Appliances, one of the leading respirator manufacturers, and Survivair's Quick2000, the type purchased for federal workers on Capitol Hill. They're each about $180. Both of these hoods require wearers to draw in the air themselves through the filter -- fine for normal people but a potential hardship for those with respiratory problems.

Hoods can be used only once.

These devices join products that have been marketed to frequent travelers in recent years: smoke hoods. Smoke hoods are specifically designed to protect against deadly carbon monoxide during a fire. They don't protect against nerve gas.

No mask or hood lasts forever. Its filter will eventually get clogged.


Respirator companies don't make products in sizes that will fit children. You may be able to find N95 respirators sized for smaller adults. The challenge will be fitting it to a child's face to keep out contaminated air.

Some escape-hood manufacturers make products just for children. ILC Dover says its Baby SCape hood fits children ages 3 and younger. Safer America, a New York store, sells several hoods and suits for children, toddlers and babies, at $295 to $500.

With their smaller lungs, children may have trouble pulling air in through a filter. Most children's hoods or masks are supplied air, meaning a motor blows air into the unit.

ILC Dover also makes a clear plastic, air-filtering container into which owners can insert a dog or cat in a kennel. The Pet Shield is $350 for animals up to 50 pounds, $450 for those 50 to 100 pounds.

Where to get them: Locally, Geomet Technologies Inc. distributes a wide range of gas masks and escape hoods: or 301-428-9898. Safer America is at or 877-774-4055. MSA sells its Gas Mask Hood through; information is at, or call 888-672-4692. ILC Dover sells through its Web site:, or call 800-631-9567. The Quick2000 is available through Survivair:, or call 888-274-8535.

How a Masks Works

All respirators stop working eventually, though in the case of half-masks and military-style gas masks, filter canisters can be replaced. To understand why, it's useful to know how respirators work in the first place:

An N95, P100 or HEPA filter acts like the colander you dump boiled pasta into: It simply allows small things through while stopping big things. Those big things include dangerous spores and debris. The small things are molecules of air.

Activated charcoal, the magic ingredient in masks that neutralize nerve gas and harmful chemicals, works in a different way. Imagine a river that widens into a huge lake before narrowing and continuing its flow. The lake is speckled with millions of tiny inlets. That's a piece of activated charcoal. Now imagine millions of speedboats racing down the river. The boats are the molecules of a dangerous chemical. Instead of continuing its journey to the sea, each speedboat docks in a different inlet as it enters the lake.

As long as there are more inlets than boats -- or more pores in the charcoal than chemical molecules -- the wearer is safe.

But no filter lasts forever. A particulate filter will eventually become so clogged with particles that oxygen won't penetrate it. Bad news for the wearer. And an activated charcoal mask will eventually lose its chemical-cleansing abilities, allowing untreated air to enter. Bad news for the wearer if that air contains something dangerous.

A hood or mask could stop working in less than 20 minutes, depending on how contaminated the air was. The batteries in powered-air units typically conk out after about four hours, though the filter may have been overrun long before then.

-- John F. Kelly
Washington Post Staff Writer