I believe you may be incorrect, the fraction is not the problem [1]. Apollo also ran with pure O2, even after an early accident under higher pressure [2]. > In

I believe you may be incorrect, the fraction is not the problem [1]. Apollo also ran with pure O2, even after an early accident under higher pressure [2]. > In such applications as extra-vehicular activity, high-fraction oxygen is non-toxic, even at breathing mixture fractions approaching 100%, because the oxygen partial pressure is not allowed to chronically exceed 0.3 bar (4.4 psi). 1. https://en.m.wikipedia.org/wiki/Oxygen_toxicity https://en.m.wikipedia.org/wiki/Oxygen_toxicity 2. https://www.popsci.com/why-did-nasa-still-use-pure-oxygen-after-apollo-1-fire/ https://www.popsci.com/why-did-nasa-still-use-pure-oxygen-af...