Instead of an oxygen tank, get a 'window breaker'

Some cars can be ordered with fire extinguisher, so yeah, mount it properly and it should by fine.

But can you please share with us why you would put in an oxygen tank?

just an sudden idea, since im asking about fire extinguisher already, as well as ask oxygen tank too.

Remember to get the right type of fire extinguisher. Not all are the same, and they have expiry date as well.

Fire extinguisher and life hammer to cut seat belt and smash glass

http://www.lifehammer.com/

Oxygen tanks when damaged tend to go boom.

What ever happened to just a plain old first aid kit?

If ur going as far as O2 tank, dun forget d mask, regulating valve, pipes etc. Or mayb u can add a satellite phone with some spare battery n a heart resuscitating machine.