Carbon monoxide — workplace exposure limit
What is the pel (ppm) for Carbon monoxide — workplace exposure limit?
For Carbon monoxide, pel (ppm) is 50; pel (mg/m³) is 55; cas no. is 630-08-0, verified against its source on 2026-08-05.
Carbon monoxide | 630-08-0 | 50 | 55 | - |
— osha.gov, retrieved 2026-08-05
50
The most of this substance workplace air may legally contain, averaged over an 8-hour shift — OSHA's permissible exposure limit (PEL), in parts per million, from the agency's own table row quoted below. Where federal OSHA and Cal/OSHA disagree, both limits are stated, each with its own agency's table row as evidence. NIOSH's number, where there is one, is shown separately: it is a recommended limit, not a legal one, and it is often the strictest of the three.
- Substance
- Carbon monoxide verified
- CAS No.
- 630-08-0 verified
- PEL (ppm)
- 50 verified
- PEL (mg/m³)
- 55 verified
- Ceiling
- 200 ppm per dir.ca.gov
- NIOSH REL (ppm)
- TWA 35 per cdc.gov
- NIOSH REL (mg/m³)
- 40 per cdc.gov
What cdc.gov says
NIOSH REL TWA 35 ppm (40 mg/m3) C 200 ppm (229 mg/m3)
— cdc.gov, retrieved 2026-09-08
Sources disagree
More than one authority states this, and they do not state the same thing. Both are reproduced with the source each came from — deciding between them is yours, not ours.
PEL (ppm)
osha.gov says pel (ppm) is 50, as of 2026-08-05.
Carbon monoxide | 630-08-0 | 50 | 55 | - |
https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000TableZ1
dir.ca.gov says pel (ppm) is 25, as of 2026-08-05.
630080 | | Carbon monoxide | 25 | 29 | 200 ppm
https://www.dir.ca.gov/title8/5155.html
PEL (mg/m³)
osha.gov says pel (mg/m³) is 55, as of 2026-08-05.
Carbon monoxide | 630-08-0 | 50 | 55 | - |
https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000TableZ1
dir.ca.gov says pel (mg/m³) is 29, as of 2026-08-05.
630080 | | Carbon monoxide | 25 | 29 | 200 ppm
Sources
- osha.govhttps://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000TableZ1
- dir.ca.govhttps://www.dir.ca.gov/title8/5155.html
- cdc.govhttps://www.cdc.gov/niosh/npg/npgd0105.html