Another carbon dioxide question:

When I studied in Germany, there was a time when I lived in a students' dormitory and we had a very small telephone niche on our floor with a door to close in order not to disturb other students by loud talking.

Once after about half an hour of vivid talking with the door closed I felt as if I was going to faint.

I think the air volume in there was only about half as big as in a normal phone booth (their outer measures are 100x100x220 cm in Germany), but the door was less tight.

But I also know that "feeling as if" and really fainting are a long way from each other. I think there are no cases reported of sobre people fainting in phone booths.

How long can one remain concious with, say, two cubic metres of air? Or with one? Or do they have some secret airing system in there?

(good thing everyone has mobile phones now)