How does the lungs know which is O2 and CO2? We breathe a ton of different gasses daily but what happens to the other gases other than O2 and CO2 when inhaled?

Question

How does the lungs know which is O2 and CO2? We breathe a ton of different gasses daily but what happens to the other gases other than O2 and CO2 when inhaled?

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Answer 1

The human body does not monitor CO2 directly. It measures pH, which CO2 affects. It doesn’t monitor oxygen levels at all, which is why nitrogen gas is so dangerous: as long as you are breathing out CO2, you’ll feel fine – even if you aren’t getting any oxygen. There are many stories of people walking into a room filled with nitrogen and working happily for 4 minutes until they pass out and die.

Burrowing animals like rabbits and rats do actually monitor oxygen directly.