Re: air CON
large amounts of people in any space that's not getting active air replenishment is going to raise CO2 content to uncomfortable levels very very fast. And I think the poster above got his percentages off by a factor of 10. Acceptable levels are anything below 600 ppm, which is about 0.06%. Discomfort and drowsiness sets in at 0.1 to 0.25% (1000-2500 ppm), anything above that is going to cause more serious health effects.
(Source)
Normal CO2 Levels
The effects of CO2 on adults at good health can be summarized to:
normal outdoor level: 350 - 450 ppm
acceptable levels: < 600 ppm
complaints of stuffiness and odors: 600 - 1000 ppm
ASHRAE and OSHA standards: 1000 ppm
general drowsiness: 1000 - 2500 ppm
adverse health effects may be expected: 2500 - 5000 ppm
maximum allowed concentration within a 8 hour working period: 5000 - 10000 ppm
maximum allowed concentration within a 15 minute working period: 30000 ppm
The levels above are quite normal and maximum levels may occasionally happen from time to time. In general - ventilation rates should keep carbon dioxide concentrations below 1000 ppm to create indoor air quality conditions acceptable to most individuals.
Extreme and Dangerous CO2 Levels
slightly intoxicating, breathing and pulse rate increase, nausea: 30000 - 40000 ppm
above plus headaches and sight impairment: 50000 ppm
unconscious, further exposure death: 100000 ppm
Carbon Dioxide Standard Levels
The recommendations in ASHRAE standard 62-1989 are
classrooms and conference rooms 15 cfm per occupant (person)
office space and restaurants 20 cfm per occupant
hospitals 25 cfm per occupant
1 cfm (ft3/min) = 1.7 m3/h = 0.47 l/s