Also this is the inflater on the buddy commando slim-line BCD which I think is the AP jacket breathing valve/inflator which allows the user to breath in air from the BCD bladder.
Is this a typo? You do not want to breath in air from a bladder. That air tends to have all sort of pathogens in it. You blow air into a bladder to inflate it if there is a failure in the inflation system when at the surface.