This is a NASA review of the scientific understanding of oxygen toxicity circa 1964. There's a difference between pure oxygen at low pressure (as experienced by

This is a NASA review of the scientific understanding of oxygen toxicity circa 1964. There's a difference between pure oxygen at low pressure (as experienced by astronauts) and pure oxygen at high pressure (as experienced by SCUBA divers). See page 7 (pg 20 of the pdf) Another link has an interesting review of how Apollo 1 ended up with a pure oxygen atmosphere, even though NASA had originally specified a mixed-gas atmosphere: > "NASA changed its mind on the dual-gas system because weight was increasingly becoming an issue. The spacecraft was getting heavy, too heavy to launch to the Moon with the Saturn V, and shaving pounds off the top of the stack was ideal: every pound removed at the top translates to tens of additional pounds of thrust at the moment of launch. And so NASA zeroed in on the crew cabin environment as a place to save weight." - https://www.discovermagazine.com/the-sciences/why-apollo-had-a-flammable-pure-oxygen-environment https://www.discovermagazine.com/the-sciences/why-apollo-had...