Gents, Thanks again!

Spare Air ( designed for divers for out of air emergencies. HEED helicopter emergency egress device. For getting out of submerged aircraft, extrapolated by me to submerged vehicles. Attached to my vest. Rip shears and window punch secured on drivers side visor and vest. Thanks for the tip on exhaling completely on assent. I didn't know that. See ignorance can kill you.

Unworkable? Please elaborate. As above, always looking for better options. Thanks again.