You are correct.Â* Oxygen doesn't burn.Â* But it really supports combustion!

When I was in AF flight school (early 70s, so everyone smoked), they
warned us about smoking with a mask dangling along side one's face.
Seems one fighter jock had his mask catch fire (maybe while lighting up,
maybe due to a cabin depressurization causing the O2 system to go into
pressure mode, who knows?).Â* The point was that he suffered serious
burns to his face.

Personally I never felt the need to smoke during a 2-hour flight with a
pressure demand mask and regulator.

On 10/2/2019 12:09 AM, wrote:
Many moons ago when I was a junior hospital doctor in a chest ward the preferred oxygen mask for low concentration O2 was the "Edinburgh mask" which had a circular hole in the front with the O2 nozzle entering at its lower circumference. Some of the chest patients loved it because they could smoke through the hole. As was demonstrated to me by a marginally less junior doctor, if you held the lit cig tip directly in the O2 outlet flow it just glowed brighter. Oxygen doesn't burn, it burns.

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Dan, 5J