As I said in my original post:Â* The pilot was either lighting up or the
regulator gave a blast of oxygen, maybe while he was taking a drag.Â* The
mask did not combust spontaneously and I never said such.

If I had to guess, I'd say he was lighting up and, just after removing
the mask, there would be pure oxygen within the mask.Â* It would be easy
to light.

On 10/2/2019 10:17 AM, wrote:
On Wednesday, October 2, 2019 at 4:38:10 PM UTC+1, Dan Marotta wrote:
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.


An oxygen mask that combusts on exposure to oxygen would be a bit of a design flaw! There will have been something else that ignited before the mask. In the context of medical or general aviation oxygen use I would be far more concerned about oxygen exposure to petroleum based products (e.g. vaseline, Vicks, Chapstick on the face) than smoking

https://www.thoughtco.com/flammability-of-oxygen-608783

--
Dan, 5J