Some people run to the local Army-Navy surplus store and buy a mask secure in the knowledge that they will be safe in the event of an attack.
Looking at the movies you get the impression that there's nothing more to gas masks than pulling it over your face and you're safe. The reality, however, is altogether different. Gas masks are complex pieces of equipment. To use them inappropriately is potentially more dangerous that the chemical they're supposed to protect you from.
Having many years experience with Chemical & Biological weapons, I'll attempt to lay aside the myth of the gas mask and put you in a position to make a reasoned decision on whether you should use them or not.
This is the million dollar question. Most experts would advise that stocking up on gas masks for the whole family is not worth it. An appropriate gas mask will protect you from breathing in most chemical or biological agents, BUT there are some things to bear in mind before you run out to buy one:
A gas mask will be effective IF you're wearing it before exposure to the agent or immediately upon exposure. If you're inexperienced in the use of gas masks, or if you take to long to find it, you may be putting your life more in danger than if you simply moved quickly to escape the cloud. Of course there's every chance that you will not know what kind of poison is in the air and may not have the appropriate filter in your mask. This may lead to a false sense of security.
In the case of a biological attack masks are of little use. In most cases a biological attack will go undetected for at least several days making the gas mask virtually redundant.
It's also worth bearing in mind that gas masks are quite expensive. You can expect to spend about $200 for an effective mask. Then you need to decide if (1 you're going to carry the mask with you everywhere you go which would be uncomfortable, impractical and probably not too popular an idea with the kids or (2 you're going to have one mask for home, one for work, one for the car, and so on which would be very expensive.
In the case of a biological attack, breathing through a doubled-up t-shirt will greatly increase your chances of survival in an emergency situation. Unfortunately, this method isn't effective against most chemical agents.
I would suggest that a gas mask, used properly, would be useful in the event of an attack (provided you know how to use it and you're aware of the attack in time to put it on). However, I would not feel compelled - despite current threats - to rush out and invest large amounts of money in them.
Gas mask filters have a limited life-span. Most of them have just a few hours of active use (depending on the amount of dangerous substance being filtered and the relative air humidity). At this point the filter needs to be changed. Never buy a second-hand mask as you will not know how much life the filter has left in it.
You'll need precise instructions on using your gas mask. There's more to it than just pulling it over your face. Inappropriate use may be more dangerous than the substance you're trying to protect yourself against. Ideally you should get some training on the correct use of gas masks and both you and your family should practice using them regularly.
You should be clean-shaven when putting on your gas mask. A beard (or even stubble) may enable the poisons to infiltrate the mask.
If you've had no training in the use of gas masks, there's one important point to remember - take the plastic seal off the filter before putting the mask on. During Operation Desert Storm (1990) eight people lost their lives because they forgot to remove the seal (they thought they were being poisoned, when in fact it was the mask that was smothering them).
Some gas mask filters have larger intake openings designed for people with lung/breathing problems.
Increasingly, gas masks are available in various sizes - even for children and babies. If you're buying gas masks for your family, then be sure that each one has a perfect fit. Some masks are equipped with drinking systems, and masks that enable easier speech (via 'voice-mitter') are also available.
Don't buy masks via mail-order or over the Internet as you can't be sure that they'll fit properly. Always buy them in person from a professional who knows what he/she is talking about. Be sure to get a mask fitted for everyone in the family. To my knowledge, there are currently no gas masks available for pets...
Bear in mind that, while gas masks are effective against most chemical and biological agents, they do not assure protection against everything. Be sure to get a gas mask that is certified to be effective against chemical and biological weapons agents.
Generally, for biological agents to be effective, they need to be between 1 and 5 microns in diameter. For this reason, regular surgical masks, which are relatively cheap, would protect you against almost all biological threats. Protection against chemical agents, however, requires a gas mask.
If you have a baby or a young infant who is reluctant to put on a gas mask during an attack, then don't waste time struggling. Strive instead, to get both yourself and the child to a safe place as quickly as possible. It's for this reason also, that it's vital that you practice proper gas mask usage with your family -- particularly young children.
There are a number of important points to bear in mind when buying a gas mask:
While there have been some advances lately in the production of gas masks for women, children and people with smaller faces, a lot of the masks on the market are designed with the adult male (military) face in mind.
Be sure to buy a mask that fits perfectly otherwise it will only give you a false sense of security (there's no point in a filter that keeps out bacteria at 0.3 microns if you've got 1mm of space between your face and the mask (which is why you have to be clean-shaven before putting on the mask). Of course, you would need to have a mask fitted individually for every member of your family.
Make sure that your gas mask is certified against chemical and biological warfare agents. But, bear in mind that no matter how good the gas mask is, the filter will not protect you against everything. You may need to get different sets of filters with your mask to have the broadest protection possible. Be sure to discuss this issue thoroughly with potential suppliers before buying.
Don't buy your gas mask from surplus 'Army-Navy' type stores. The gas masks you'll find here have most likely been used in military exercises, may be out of date and very possibly contain flaws in the structure (small cracks or holes in the rubber). If you are buying a mask, buy one from a reputable manufacturer and buy it in person with every member of your family available for a fitting.
The best masks are those with HEPA filter* (ideally coupled with chromium-free impregnated carbon, that filters both inorganic warfare agents like cyanide, chlorine and phosgene, as well as organic agents like VX, sarin, tabun, mustard gas and lewisite). Some gas masks can even protect you against acid gases and ammonia.
Appropriate protective clothing can prevent exposure through the skin.
Protective suits usually come with built-in boots and hood. They can protect against liquid and vapor chemical warfare agents, as well as against biological warfare agents.
Several sizes exist, including those for children.
Protective boots are usually designed especially to accommodate the extra bulk of a protective suit, and remain relatively easy to put on even if you're wearing protective gloves. Protective boots are usually knee high and have a high chemical resistance.
Protective gloves are extremely solid, they can be as thick as 25mm and have a particularly long chemical resistance, resisting most toxic/hazardous chemicals.
Like gas masks, I would need to question the practicality of buying protective suits. Obviously, you wouldn't be able to carry one around with you everywhere you go (you're kids would definitely draw the line on that one!), and the cost of keeping a suit everywhere is prohibitive.
And, like gas masks, you would need to know about the attack in time to get the suit on. And again, you may be putting yourself in danger as you struggle to put on the suit when you could, instead, be making sensible efforts to escape the gas cloud.