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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
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.