Allowable Exposure Levels to Carbon Monoxide

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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.