I was wondering if it were possible for human life to survive with slightly more oxygen and slightly less nitrogen. I know a user called @Lars asked a similar question, but it didn't give a clear answer to mine.
So, on Earth, the atmosphere is about 78% nitrogen, 21% oxygen and 1% other stuff. But what would happen if there was a planet where oxygen was around 30% of the atmosphere, and nitrogen was around 69%?
Would humans, animals and plants still be able to survive with the same techniques and adaptations, or would we have to develop new ones? Would a relatively small change (compared to @Lars's) affect life as we know it?