[radlad]

> The CO₂ while on the flight was in the 3000's range.

I always assumed they intentionally messed with oxygen in the cabin to "relax" travelers.

Anecdotally, I have often experienced a sedative effect on airplanes that I do not ever experience in land vehicles.

[mlsu]

In general, anecdotes about "they raise the oxygen levels in [x] to induce [y]" are completely false. I've heard this about airplanes and casinos.

For one, it's really difficult/energy intensive to increase the level of oxygen in a space. Second, it's very very difficult to purify oxygen -- because oxygen oxidizes stuff. Even if you could do that, raising the level of oxygen is extremely dangerous, because it radically increases flammability of things and makes fire much worse. For an example of this: Apollo 1.

[tesseract]

Well, there's less of it, since typical airliner cabin pressure is equivalent to being at 8000ft altitude or so. Do you typically spend long durations driving in the mountains?

[weaksauce]

the oxygen levels in airplanes are not high because they only pressurize the cabin to be about a 7000' pressurization. that's roughly equivalent to a lot of mountain town altitudes... think flagstaff.