Allowable (Legal) Limits for Carbon Monoxide
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)
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.
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
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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.
