CO2 acceptance and comfort levels
Indoor air quality includes
- temperature
- odor
- high or low levels of gases
Since CO2 is exhaled by people at predictable levels
the content of Carbon Dioxide - CO2 - in air may be a significant indication of air quality.
A measure of CO2 indicates the amount of fresh air supply:
- 15 cfm ventilation rate per occupant corresponds to 1000 ppm CO2
- 20 cfm ventilation rate per occupant corresponds to 800 ppm CO2
Normal CO2 Levels
The effects of increased CO2 levels on adults at good health
can be summarized:
- normal outdoor level: 350 - 450 ppm
- acceptable levels: < 600 ppm
- complaints of stiffness and odors: 600 - 1000 ppm
- ASHRAE and OSHA standards: 1000 ppm
- general drowsiness: 1000 - 2500 ppm
- adverse health effects expected: 2500 - 5000 ppm
- maximum allowed concentration within a 8 hour working period: 5000 ppm
The levels above are quite normal and maximum levels may occasionally happen from time to time.
Extreme and Dangerous CO2 Levels
- slightly intoxicating, breathing and pulse rate increase, nausea: 30,000 ppm
- above plus headaches and sight impairment: 50,000 ppm
- unconscious, further exposure death: 100.000 ppm
Carbon Dioxide Standard Levels
The recommendation in ASHRAE standard 62-1989 are
- classrooms and conference rooms 15 cfm per occupant
- office space and restaurants 20 cfm per occupant
- hospitals 25 cfm per occupant
© The Engineering ToolBox 2005
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