Re: Oxygen makes things burn brightly
"As pure oxygen is toxic above 0.5 atmospheres, it seems unlikely it was both "pure" and "high pressure"...."
I think it was both, an initial 100% oxygen at slightly higher than atmospheric reducing to 100% at ~1/3 atm. for almost all of the flight. I think after the fire they changed to using oxygen/nitrogen.
I didn't downvote BTW - you are quite correct about oxygen tox.