# Mesityl oxide; 4-methyl-3-pentene-2-one — US workplace chemical exposure limits: federal OSHA vs Cal/OSHA, side by side

For Mesityl oxide; 4-methyl-3-pentene-2-one, pel (ppm) is 15; pel (mg/m³) is 60; stel (ppm) is 25; stel (mg/m³) is 100, verified against its source on 2026-08-05.

- **Substance:** Mesityl oxide; 4-methyl-3-pentene-2-one
- **PEL (ppm):** 15
- **PEL (mg/m³):** 60
- **STEL (ppm):** 25
- **STEL (mg/m³):** 100

## What the source says

> 141797 | | Mesityl oxide; 4-methyl-3-pentene-2-one | 15 | 60 | | 25 | 100

## Source

- 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/).