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Occupational Safety & Health Administration, USA (OSHA) (for
industrial situations)
Permissible Exposure Limit (PEL, by TWA) - 50 ppm, 8 hrs.
Old PEL Standard (by TWA) - 35 ppm, 8 hrs.
Threshold Limit Value (TLV, by TWA) - 25 ppm (29 mg/cu. m)
(recommended by Amer. Conf. of Governmental & Industrial Hygienists
ACGIH)
Ceiling (max. value, 15 min.) - 200 ppm (229 mg/cu. m)
MI Occup. Safety & Health Admin. (MIOSHA)
PEL (Industry, by TWA) - 35 ppm, 8 hrs. (38.5 mg/cu. m)
PEL (Construction, by TWA) - 50 ppm, 8 hrs. (55 mg/cu. m)
Ceiling (max. value) - 200 ppm (229 mg/cu. m)
Environmental Protection Agency, USA (EPA)
Domestic, outdoor air, all ages (TWA) - 9 ppm*, 8 hrs.
Domestic, outdoor air, all ages (TWA) - 35 ppm, 1 hr.
World Health Organization (WHO)
Domestic, outdoor air, all ages (TWA) - 9 ppm*, 8 hrs.
Am. Soc. of Heating, Refrigeration & Air Cond. Engineers (ASHRAE)
Indoor air (leakage at a heat register) - 9 ppm
American Gas Association
Indoor air (leakage at a heat register) - 15 ppm
TWA - Computed by making measurements at intervals over 8 hours,
then adding the sums of the concentrations and the intervals,
and dividing by 8 hours (480 min.).
* Based on several published studies of people with coronary
ischemic disease showing ECG changes during moderate exercise
when breathing concentrations of CO giving 3% COHb.
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