# Calcium oxide — US workplace chemical exposure limits: federal OSHA vs Cal/OSHA, side by side

For Calcium oxide, cas no. is 1305-78-8; pel (mg/m³) is 5, verified against its source on 2026-08-05.

- **Substance:** Calcium oxide
- **CAS No.:** 1305-78-8
- **PEL (mg/m³):** 5

## What the source says

> Calcium oxide | 1305-78-8 | - | 5 | - |

## 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.

### PEL (mg/m³)

osha.gov says pel (mg/m³) is **5**, as of 2026-08-05.

> Calcium oxide | 1305-78-8 | - | 5 | - |

Source: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000TableZ1

dir.ca.gov says pel (mg/m³) is **2**, as of 2026-08-05.

> 1305788 | | Calcium oxide | -- | 2

Source: https://www.dir.ca.gov/title8/5155.html


## Source

- https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000TableZ1
- https://www.dir.ca.gov/title8/5155.html

Last verified: 2026-08-05. Review by: 2027-08-05.
Part of [US workplace chemical exposure limits: federal OSHA vs Cal/OSHA, side by side](https://referencesource.org/workplace-exposure-limits/).