you see the problem with this is that we can say that the auditorium has an increase in CO2% and still consider O2 % to remain the same. This is a false position IMO. If ambient air has and increase of 10 % CO2 in a air gas population of 100% what gas is being reduced? Oxygen% must be effected by the increase in CO2. The reason we are gasping for air is because there is a lack of oxygen to breath IMO.