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Why are we so concerned with oxygen production yet we never hear about nitrogen production, though we actually need 78% nitrogen vs 21% oxygen to survive? (lemmy.ca)
submitted 1 year ago* (last edited 1 year ago) by LillyPip@lemmy.ca to c/askscience@lemmy.world
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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.

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[–] Brokkr@lemmy.world 1 points 1 year ago

New comment based on your edits.

When we breath, we use the oxygen, but we do not use the nitrogen. The nitrogen can actually be replaced with another inert gas and the "air" is breathable. Thinking about diving specifically, nitrox is actually an oxygen rich (nitrogen poor) mixture. More extreme mixtures use helium in place of some nitrogen (and sometime oxygen depending on the depth).

In your body, the amount of oxygen in our blood is critical for survival. Having a lot of nitrogen is actually not good. Too much is what causes the "bends", again related to diving.

When looking at exoplanet atmospheres, we look for oxygen rich because it likely indicates water. We believe that planets with a high amount of water are more likely to support life similar to ours. It is possible that another form of life exists that doesn't need oxygen or water, but we know for certain that oxygen and water can support life.

[–] sexy_peach@feddit.de 0 points 1 year ago (1 children)

It's about CO2 concentration, not about oxygen production.

[–] LillyPip@lemmy.ca 0 points 1 year ago* (last edited 1 year ago) (2 children)

That makes sense, thanks, since our threshold for co2 is less than 0.5%.

I may have worded my question poorly; I’m more asking why low oxygen is a problem vs low nitrogen. In retrospect, my climate focus may be distracting. It was what made me wonder about this in the first place, but the medical and scuba points are much more relevant. That has little to do with co2 (I think?) and more to do with the relative compounds in our air.

I’m still confused why we hear about oxygen but never nitrogen. Another example: when we look for habitable planets, the focus is ‘oxygen rich atmosphere’, but not ‘nitrogen rich’.

[–] sexy_peach@feddit.de 1 points 1 year ago

Maybe nitrogen could be replaced with other gases, but we need oxygen in our lungs and bloodstream to survive. So maybe it's more important for our survival?

[–] xantoxis@lemmy.world 0 points 1 year ago* (last edited 1 year ago) (1 children)

As someone else pointed out, nitrogen is non-reactive. Almost any gas would work, as long as it was plentiful enough to maintain the necessary air pressure, and non-reactive. You don't need nitrogen to live; you just need oxygen. Just, not so much that you get acute oxygen toxicity, which mainly happens with pure oxygen at regular atmospheric pressure for extended periods of time. There are even applications where pure oxygen is administered to people, usually at lower than atmospheric pressure.

Nitrogen is a filler gas. It's there to take up space and keep the air molecules bouncing around at the appropriate pressure. (Or perhaps it would be more accurate to say our lungs require a certain pressure because this is where we evolved; that pressure happens to be maintained mostly by nitrogen.)

We aren't exploring other planets in person yet, but if we were, we'd need to filter out all the bad shit in the air, keep the oxygen, and maintain the normal pressure. If we were lucky enough to encounter an atmosphere with oxygen, a non-reactive filler gas, and no toxins, we might be able to just breathe it; or to breathe it after compressing it to the appropriate pressure. Nitrogen wouldn't need to be there at all.

The confusing thing about the scuba application is that nitrogen isn't in the mix because you need the nitrogen. It's there because it reduces the pressure of toxic gases to a threshhold you can survive.

[–] LillyPip@lemmy.ca 0 points 1 year ago (1 children)

Thank you for your detailed response. That explains things very well. I don’t know a lot about chemistry, but is oxygen specifically required for cell metabolism or could that be replaced with a similarly reactive gas, too?

[–] ASeriesOfPoorChoices@lemmy.world 1 points 1 year ago

This is why:

A) in spaceships, you can have 100% oxygen environments, at low pressures

B) scuba divers replace nitrogen with helium for deep dives (trimix) - and reduce oxygen.

As for replace oxygen: yes, but that would kill us very quickly.