CSLB C-20 HVAC ContractorControls, Electrical and SafetyMedium
Per Cal/OSHA regulations, what is the permissible exposure limit (PEL) for carbon monoxide as an 8-hour time-weighted average?
- A100 ppm
- B9 ppm
- C25 ppm
- D50 ppm
Show answer & explanationAnswer & explanation
Correct answer: C. 25 ppm
Cal/OSHA sets the permissible exposure limit for carbon monoxide at 25 ppm as an 8-hour time-weighted average (TWA), which is stricter than the federal OSHA PEL of 50 ppm. Technicians working around combustion appliances must be aware of this stricter California standard.
Why the other options are wrong
- A. 100 ppm is far above any recognized occupational exposure limit for CO.
- B. 9 ppm is closer to some indoor air quality guideline values, not the Cal/OSHA PEL.
- D. 50 ppm is the federal OSHA PEL, which California has replaced with a stricter limit.
Cal/OSHA CO PEL
Cal/OSHA establishes a permissible exposure limit of 25 ppm for carbon monoxide as an 8-hour time-weighted average, stricter than the federal 50 ppm PEL.
- California PEL: 25 ppm (8-hr TWA)
- Federal OSHA PEL: 50 ppm (8-hr TWA)
- CO is colorless, odorless, and produced by incomplete combustion
Memory trick: California cuts it to twenty-five.