[ErroneousBosh]

> The article references a study where the CO2 proportion going from 0.04% -to 0.25% causes mental problems. In other words, a difference in 0.21% of the air.

I'm finding that pretty difficult to believe, to be quite honest with you.

And before you say "aha, carbon dioxide brain fog!" consider that I'm about a mile from the sea with a 40mph onshore breeze. This air is about as oxygenated as it gets.

[anon7000]

It makes a lot of sense actually. You get severe symptoms when CO2 makes up only a couple % of the air. And can become fatal at like 5%. There’s not like a hard line where you suddenly die, it’s a gradual thing. It very much makes sense that we’d notice minor symptoms at a few thousand PPM when it only takes like ten thousand to feel it severely.

[Hikikomori]

I got a monitor as we had an old apartment with bad ventilation. When I started feeling it I would check and it was always around 1200ppm and would open a window for a bit. Outside air is around 420ppm, but that's not the problem, enclosed and badly ventilated rooms are if you spend a few hours in there.

[Terr_]

1% (10,000 ppm) is enough for the person to become aware something is odd through drowsiness or an elevated heart rate.

I don't think it's too far-fetched for a quarter of that to cause subconscious cognitive effects, that could be measured in tests.

[ErroneousBosh]

The air in your lungs sits around 40,000ppm or 4% carbon dioxide.

In every breath you remove about 25% of the oxygen from the air in your lungs, which is why mouth-to-mouth resuscitation works, at all. Most of the oxygen is still in there.

To be clear, that 25% represents a change in oxygen level from around 21% to around 16%, so the few tenths of a percent change in carbon dioxide just isn't a huge amount.