Carbon dioxide (CO2) is a colorless, odorless, non-flammable gas that is a product of cellular respiration and burning of fossil fuels. It has a molecular weight of 44.01g/mol (NIOSH 1976). Although it is typically present as a gas, carbon dioxide also can be a solid form as dry ice and liquefied, depending on temperature and pressure (Nelson 2000).

CO2is present in the atmosphere at 0.035% (Aerias 2005; CCOHS 2005). In terms of worker safety, Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit (PEL) for CO2 of 5,000 parts per million (ppm) over an 8-hour work day, which is equivalent to 0.5% by volume of air. Similarly, the American Conference of Governmental Industrial Hygienists (ACGIH) TLV (threshold limit value) is 5,000 ppm for an 8-hour workday, with a ceiling exposure limit of 30,000 ppm for a 10-minute period based on acute inhalation data (MDPH 2005; NIOSH 1976). A value of 40,000 ppm is considered immediately dangerous to life and health based on the fact that a 30-minute exposure to 50,000 ppm produces intoxication, and concentrations greater than that (7-10%) produce unconsciousness (NIOSH 1996; Tox. Review 2005). Additionally, acute toxicity data show the lethal concentration low (LCLo) for CO2 is 90,000 ppm (9%) over 5 minutes (NIOSH 1996). See Table 1 for a listing of regulatory agency standards for acceptable CO2 concentrations in the workplace. CO2 is a good indicator of proper building ventilation and indoor air exchange rates. Consequently, it is measured in buildings to determine if the indoor air quaity is adequate for humans to occupy the building [e.g. laboratory fume hoods] (MDPH 2005).[1]

Standards of CO2 in workplace

U.S. standards of CO2 in workplace


  1. BLM. Standards of CO2 within the workplace.