The primary component of a respirator is the facepiece.  The facepiece is typically where a respirator attaches to the user, although there are also other connections such as hoods, helmets and mouth-bits that provide protection to the user by isolating them from the surrounding atmosphere.

The type of facepiece used affects how well the respirator seals against the user’s face which, in turn, dictates the amount of inward leakage in negative pressure phases (when the user during the breathing cycle).