Escape respirators, which also are known as escape hoods, come in two types. One type, called a self contained escape respirator, consists of a hood with a tightly fitting neck piece and a contained source of breathing air. The hood provides a barrier against contaminated outside air, and the user breathes air from the attached source. In the other type, called an air purifying escape respirator, a filter canister is mounted on the hood. The user breathes outside air through the canister, which filters out harmful contaminants before the air is breathed.