My idea.. =)

[figgie]

Well... that's not entirely correct, there's no firewall between nitrous bottles and you, but that's a special case.

Nitrous by itself is not combustible.

Don't believe me? Take a Plain old NOS bottle and pipe it and then put a light at the other end. Turn on Nitrous, watch as nothing happens. For Nitrous to work it has to see the 1000+ degree tempratures that are in the cylinder

 

[jetjock]

Yep, it's just an oxidizer. No more flammable than oxygen.

 

[IJ.]

A leak without a firewall would help owning a 7M