I stumbled across this, and thought it was worth sharing. My military scout swimmer's vest has a Schrader valve underneath the CO2 cartridge detonator. The valve functions as a one way valve, so that in the event of a cartridge detonator failure, the CO2 is retained inside the vest and would not leak out. This is a handy piece of information, especially if you have a vintage BCD that has the fitting for the cartridge detonator, but not the detonator itself. All of these brass fittings are threaded on the inside, and they can all take a Schrader valve. I checked my Aqualung horsecollar, Nemrod vest, and my Stebco Mae West.
Observe:
Pretty cool, right? You can run a vest with a busted or missing cartridge detonator like this. It also minimizes failure points.