Excess oxygen is actually harmful to humans, but all the climate warnings are about losing oxygen, not nitrogen edit: but when we look for habitable planets, our focus is ‘oxygen rich atmosphere’, not ‘nitrogen rich’, and in medical settings, we’re always concerned about low oxygen, not nitrogen.
Deep sea divers also use a nitrogen mix (nitrox) to stay alive and help prevent the bends, so nitrogen seems pretty important.
It seems weird that our main focus is oxygen when our main air intake is nitrogen. What am I missing?
edit: my climate example was poor and I think misleading. Added a better example instead.
When scuba diving recreationaly, Nitrox tanks actually have higher concentrations of oxygen, leaving less “space” for nitrogen and other gases.
Normal air tanks are filled at 21% oxygen. A nitrox tank will have more than 21%. The ones I use have 32% oxygen, wich helps when being at depths between ~20m and ~40m
I know that technical divers do use other gas concentrations, and they even change the nitrogen in the tanks for other inert gasses. But I’ve no idea of which gasses they use.
The most famous is Heliox, 98% helium and 2% oxygen iirc.