search widget
Hartford and Ratliff Co. has certified technicians to take care of your AC installation near Novi MI.
Hartford & Ratliff Co., Inc.
The Original Hot Water Specialists Since 1955

(248) 471-3110
For Parts: (800) 466-3110
Hartford and Ratliff Co. has been a trusted Air Conditioning contractor in Farmington MI since 1955.
Hartford & Ratliff Co., Inc.
For Parts: (800) 466-3110

Allowable Exposure Levels to Carbon Monoxide

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.
24 Hour Emergency Service  •  Call Us Today  •  (248) 471-3110  •  or  •  Schedule Service Online
24 Hour Emergency Service
(248) 471-3110
Schedule Service Online
We service most AC brands and models near Farmington MI.
Hartford & Ratliff Co., Inc.
Farmington, MI 48336
Phone: (248) 471-3110
Toll Free: (800) 466-3110
Follow us on Facebook for AC repair near Farmington MI.
For AC repair in Farmington MI, find us on Google!
Read our blog for helpful Air Conditioning maintenance tips.