I am trying to optimize my indoor CO2 levels.

I bought a monitor, which seems to be fairly accurate: When I air my flat thoroughly, for 30min with fans running, I am able to achieve about 450 ppm CO2, which is about the level of the atmosphere.

I have read, that even a slight increase in Co2 to about 1000 ppm (which can be found indoors quite often) can result in 15% reduced brain performance.

I wonder, what is the bottom level of CO2, below which the body starts to perform worse, instead of better?

Before the industrial revolution, the CO2 level was half of what it is now. Does this increase already have a detrimental health effect?

If we could choose the optimal CO2 level for maximum brain performance, what would it be?

I am aware, that it would not be practical, to try to reduce the Co2 levels indoors below the outside level of 400 ppm. But I am trying to decide, if it makes sense, to try to achieve an avg. of 500, or if it would not make a big difference if it is say 800 on avg.

Source: https://ehp.niehs.nih.gov/doi/pdf/10.1289/ehp.1510037

  • 2
    If you're asking what level of CO2 in external air is "too low", there isn't one. Have you searched to find out why excess external CO2 can impair cognitive performance? Answering that question may help you understand.
    – De Novo
    Feb 10, 2019 at 4:47
  • 2
    I agree with @DeNovo regarding lack of prior research. I also have doubts about the cited study. It was extremely low power (24 subjects sampled over 6 days), and differences in cognitive function on the order of 61% and 101% are hard to believe.
    – Carey Gregory
    Feb 10, 2019 at 5:34
  • Well in trimix diving they don't worry about Co2, so I guess it's not absolutely needed. I do know that Co2 is what makes you feel the need to take a breath when freediving. Feb 10, 2019 at 9:40
  • 2
    CO2 is a byproduct of cellular respiration. If you are biologically alive, you're producing CO2 constantly that needs to be expelled. That is the CO2 your body is sensing, not atmospheric CO2.
    – Carey Gregory
    Feb 10, 2019 at 17:27


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