Hypothetically, if a person is breathing an atmosphere for a long period of time, that has too much carbon dioxide in it, enough that would normally cause lethally low blood oxygen levels, but the same atmosphere also has way too much oxygen in it, is it even theoretically possible for too much oxygen to balance/counteract too much carbon dioxide?

I tried internet searching this several times with different keywords and arrangements, I got no relevant results. All I can find are results about CO2 poisoning OR O2 poisoning NOT both at the same time.

I also searched the stack-exchange network, I can't find anyone asking this before.

1 Answer 1


CO2 is a simple asphyxiant, which means it's only toxic when it's displacing oxygen. And since your question proposes that the O2 level is being supplemented, then if the percentage of O2 in the air remains about its normal level of 21% and the other gases are inert, such as CO2, nitrogen, argon, etc, then it will be harmless.


What are the health effects of carbon dioxide? CO2 is considered to be minimally toxic by inhalation. The primary health effects caused by CO2 are the result of its behavior as a simple asphyxiant. A simple asphyxiant is a gas which reduces or displaces the normal oxygen in breathing air.

  • This answer was helpful and the link too, yes and thank you. It looks like I forgot to mention that the hypothetical atmosphere I'm thinking of would be anywhere from 10s of times Earth atmospheric pressure, to 1,000s of times atmospheric pressure. My hypothetical is a person is breathing 100+ or many many more times the amount of O2 per cubic meter of air with the resulting extreme oxygen toxicity being counteracted/balanced by a CO2 level such as a 1/4th CO2 to O2 ratio. I probably forgot to account for some physics principles too. Maybe with a blower/mixer to stop gas separation? Commented Jan 6, 2023 at 0:53
  • @TheTranscendentian Well, glad to hear it was helpful. An upvote and accepting the answer would be appreciated. In the future, hypothetical questions like this are probably better directed to WorldBuilding.SE.
    – Carey Gregory
    Commented Jan 6, 2023 at 1:09

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