Carbon Dioxide Concentration - Comfort Levels

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Indoor comfort and air quality includes parameters like

• temperature
• odor
• high or low levels of gases

Since CO2 is exhaled by people at predictable levels the content of Carbon Dioxide in the indoor air can be used as a significant indication of air quality.

Fresh supply air correlates to the indoor level of CO2 as:

• 15 cfm ventilation rate per occupant - aprox. 1000 ppm CO2
• 20 cfm ventilation rate per occupant - aprox. 800 ppm CO2

• ppm - parts per million

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.

• Carbon Dioxide Emission from the Human Body vs. Activity

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

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Unit Converter

Temperature oC K oF

Length m km in ft yards miles naut miles

Area m2 km2 in2 ft2 miles2 acres

Volume m3 liters in3 ft3 us gal

Weight kgf N lbf

Velocity m/s km/h ft/min ft/s mph knots

Pressure Pa bar atmosphere mm H2O kg/cm2 psi inches H2O

Flow m3/s m3/h US gpm cfm

11.6.8

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