system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Would there be any side effects if human started breathing 100% O2?

So when we inhale, we not only breath in O2, but also nitrogen and Co2 (Oxygen 21%, Nitrogen 79% and Carbon dioxide 0.04%). What would happen if a human being would only breath in 100% Oxygen? Can person survive in such environment?
gpt
There is a thing called oxygen poisoning which is the result of too much oxygen in the lungs. However if you lower the pressure you end up with just as much oxygen as in normal atmosphere. This is used in some space capsules and in space suits.