Hydrogen cyanide — workplace exposure limit
What is the pel (ppm) for Hydrogen cyanide — workplace exposure limit?
For Hydrogen cyanide, pel (ppm) is 10; pel (mg/m³) is 11; cas no. is 74-90-8, verified against its source on 2026-08-05.
Hydrogen cyanide | 74-90-8 | 10 | 11 | X |
— osha.gov, retrieved 2026-08-05
10
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
- Hydrogen cyanide verified
- CAS No.
- 74-90-8 verified
- PEL (ppm)
- 10 verified
- PEL (mg/m³)
- 11 verified
- Ceiling
- C per dir.ca.gov
- NIOSH REL (ppm)
- ST 4.7 per cdc.gov
- NIOSH REL (mg/m³)
- 5 per cdc.gov
What cdc.gov says
NIOSH REL ST 4.7 ppm (5 mg/m3) [skin]
— 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 10, as of 2026-08-05.
Hydrogen cyanide | 74-90-8 | 10 | 11 | X |
https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000TableZ1
dir.ca.gov says pel (ppm) is 4.7, as of 2026-08-05.
74908 | S | Hydrogen cyanide | 4.7 | 5 | C
https://www.dir.ca.gov/title8/5155.html
PEL (mg/m³)
osha.gov says pel (mg/m³) is 11, as of 2026-08-05.
Hydrogen cyanide | 74-90-8 | 10 | 11 | X |
https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000TableZ1
dir.ca.gov says pel (mg/m³) is 5, as of 2026-08-05.
74908 | S | Hydrogen cyanide | 4.7 | 5 | C
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/npgd0333.html