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 American Conference of Governmental & Industrial Hygienists ACGIH) Ceiling (max. value, 15 min.) - 200 ppm (229 mg/cu. m)
MI Occupational Safety & Health Administration (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)
American Society of Heating, Refrigeration & Air Conditioning Engineers (ASHRAE) -
Indoor air (leakage at a heat register) - 9 ppm
American Gas Association -
Indoor air (leakage at a heat register) - 15 pm
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.