>>Are you saying that the a higher CO2 level in a crowded room
>>does NOT cause drowsiness?
That is correct. As CO2 concentrations go up there is a marked increase in
respiratory minute volume, which does NOT occur in the crowded lecture
room. Therefore, increased CO2 levels are NOT a factor in "lecture room
The crowds do cause increases in temperature and humidity, along with
(mild) decreases in oxygen concentration and other, purely psychological,
effects which tend to cause the drowsiness.
BTW, if the lecturer is at all competent, there is no drowsiness.
A. M. Revzin Ph.D.