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What would happen if the atmosphere was around 90% oxygen?

Question by .: What would happen if the atmosphere was around 90% oxygen?
Could we breath? If not, what would happen and why?
What else needs to be in the atmosphere to make breathing possible?

Best answer:

Answer by charcinders
The planet would be swept by huge fires. Things that normally don’t burn like metals and animal tissue become flammable in high concentrations of oxygen.
Flammability is what keeps the oxygen level at a value of about 21%. If plants make more oxygen there are more forest fires which use up the excess oxygen.
In 1967 three astronauts testing an Apollo capsule on the ground were killed by a fire which raged through the capsule in a matter of seconds. They were using a 100% oxygen atmosphere.

Apart from the fires we could survive in pure oxygen because we don’t need anything else in the air to keep us alive. Eventually it would have harmful effects because it is a reactive gas and our bodies are not designed to handle it in high concentrations.

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