FacepieceThe body of the mask. A full facepiece covers the eyes, nose and mouth.
EyepieceThe clear window to see through. Early gas masks had round lenses of glass or mica.
Head harnessThe straps that hold the mask on. They adjust so the mask presses evenly on the face.
Seal, valves and canister 4
Face sealThe soft edge of the facepiece. It presses on the face all the way round.
Inhalation valveA flap that lets clean air in. It keeps breathed-out air from going back into the canister.
Exhalation valveA one-way valve for breathed-out air. It lets air out and stops outside air leaking in.
CanisterA container with a filter that cleans the air. It screws onto the port on the cheek.
How this list was compiled: Read 2026-10-01. (1) Wikipedia: Gas mask, https://en.wikipedia.org/wiki/Gas_mask (a sealed cover for nose and mouth that may also cover the eyes; adjustable straps; lenses to allow vision; filter containers screwed onto inlets); Respirator, https://en.wikipedia.org/wiki/Respirator (a facepiece held to the head with straps or a harness; a full facepiece covers mouth, nose and eyes and seals all round the face; inlet valves and exhalation valves; canister or chemical cartridge); Elastomeric respirator, https://en.wikipedia.org/wiki/Elastomeric_respirator (one-way valves let exhaled air out; filters in cartridges or canisters; soft seals). (2) United States federal rules, read at Cornell Law School's Legal Information Institute: 42 CFR 84.110 (a chin-style gas mask is a full facepiece, a canister usually attached to the facepiece, and connections), https://www.law.cornell.edu/cfr/text/42/84.110 ; 84.118 and 84.119 (full facepieces and eyepieces), https://www.law.cornell.edu/cfr/text/42/84.119 ; 84.120 (inhalation and exhalation valves), https://www.law.cornell.edu/cfr/text/42/84.120 ; 84.121 (adjustable head harnesses that give an even pressure on the face), https://www.law.cornell.edu/cfr/text/42/84.121 ; and 29 CFR 1910.134 (a canister or cartridge is a container with a filter, sorbent or catalyst that removes contaminants from the air passed through it; a tight-fitting facepiece forms a complete seal with the face), https://www.law.cornell.edu/cfr/text/29/1910.134 Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry; no maker's mask, nothing traced. Licence: own work
How it works
These are the parts of a gas mask of the chin style: a full facepiece with one canister. The canister is drawn unscrewed so the valve behind it shows.
Read the full guide
The mask
The facepiece covers the eyes, nose and mouth, and its soft edge seals against the face. The wearer looks through the eyepiece. The straps of the head harness hold the mask on and adjust for an even fit.
The path of the air
Air comes in through the canister, a container with a filter, and passes the inhalation valve into the mask. Breathed-out air leaves through the exhalation valve, which lets air out and none in.
Follow the air to remember the parts: canister, inhalation valve, facepiece, exhalation valve.
Questions and answers
What are the main parts of a gas mask?
The facepiece, the eyepiece, the head harness, the inhalation and exhalation valves, and the canister that holds the filter. Federal rules in the United States describe a chin-style gas mask as a full facepiece with a canister attached to it.
What does the canister on a gas mask do?
It is a container with a filter, a sorbent or a catalyst inside. Air is drawn through it on the way into the mask, and it removes particular contaminants from that air.
Is a gas mask a respirator?
Most gas masks are respirators. Respirator is the wider word: it covers everything from a paper dust mask to a full-face mask with canisters.