The scientist trying to stop you falling asleep at conferences

That might explain why some classrooms and meeting rooms consistently cause headaches, nausea or migraines, even before the sometimes boring or worrying content of the meetings is taken into account.

that explains why I was soo sleepy at major conferences- and it was not me or the paper presenters_ it was the CO2

This is something that we should also check in examination halls.

Look folks, we've all been in those rooms and I bet we've all nodded off at one time or other. I recall attending a lecture in a 250 seater room which had been in use all day and you could cut the air with a spoon. There are two issues one is ventilation and the other is temperature. Organisers should become more aware of the problem. Is there a cheap, portable CO2 monitor available somewhere? If not, there's an opportunity for someone.