Surplus gas masks are available from a wide variety of firms that specialize in army surplus equipment. There are army surplus retail outlets and literally hundreds of internet websites. The main reason people purchase gas masks of any type is usually that they feel a need to protect themselves against the possibility of a terrorist attack.

The most important feature of any gas mask should be its effectiveness against the most commonly anticipated terrorist weapons. You can discover more info about gas masks on the internet.

Next, you must research the history of the exact model of gas mask you are thinking about purchasing. It will take some time but it will make a difference. You simply must research its history and discover what that flaw was, because if it defeats the very purpose you are using it for, then perhaps you shouldn't buy it. 

However, you may discover that it functions just fine, except under extreme heat or some other situation that still makes it worthwhile for your purposes. Finally, you must check the filtration system thoroughly before you purchase surplus gas masks. 

The army surplus stores give detailed information on military gas masks, gas mask manufacturers, and the history of the gas mask.