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.
My climate example was poor, I’m sorry. A better example of what I mean is that when we look for habitable planets, our focus is ‘oxygen rich atmosphere’, not ‘nitrogen rich’, though most of our breathable air is nitrogen and too much oxygen will actually kill us.
I suppose because we don’t really use the nitrogen - it’s inert, unlike oxygen which is part of vital respiration. I’m no expert but it’s conceivable some other mix of gases could work as the inert portion besides nitrogen, but oxygen is required. Seems like it would take a lot of luck to find the right concentration though.
Calling it “inert” is misleading. It’s involved in all kinds of chemical reactions that are essential for life (and lots of non-biological reactions, too). It’s only inert in the sense that most living things can’t use it directly from the air and rely on nitrogen-fixing plants and bacteria to make it into molecules we can use.
Sure, I understand it’s one of the 3 basic plant fertilizers and plays a role in human biology. I’m referring nitrogen as a gas and its role in human respiration. It’s commonly referred to as an inert gas. I think that mainly refers to respiration and combustion.