And, the other component on a breathing loop is the carbon dioxide absorbent canister.

And a tear gas canister the size of a Pepsi can goes by my head. Whoosh!

The simplest heat engine, or hot air engine, of all time would be this take a box, a steel canister, with a piston.

(c) Respiratory protection specify appropriate types of respiratory protection based on the hazard and potential for exposure, including air purifying respirators and the proper purifying element (cartridge or canister) or breathing apparatus and

And one of the designers ran out of the room and grabbed a white board marker and a film canister which is now becoming a very precious prototyping medium and a clothespin. He taped them all together, ran back into the room and said, You mean, something like this?