A place for liquid CO2 to expand into a gas to keep the liquid out of your gun.
on hot water dispensers, a separate chamber into which expanded water flows as it is heated (and from which it is subsequently drawn out again during activation).
A device that lets CO2 expand to a consistent gas state instead of a liquid form. When CO2 is charged into a canister it becomes a liquid. CO2 gas delivers much better performance than it's liquid form.