# Benzene — workplace exposure limit

For Benzene, niosh rel (ppm) is TWA 0.1; cas no. is 71-43-2, verified against its source on 2026-09-08.

- **Substance:** Benzene _(verified: appears in its own passage below)_
- **CAS No.:** 71-43-2 _(verified: appears in its own passage below)_
- **NIOSH REL (ppm):** TWA 0.1 _(verified: appears in the quote below)_

## What the source says

> NIOSH REL Ca TWA 0.1 ppm ST 1 ppm

## Where each value comes from

This source states these in separate places, so each value is shown with the passage that states it.

### Substance

> CDC - NIOSH Pocket Guide to Chemical Hazards - Benzene

### CAS No.

> CAS No. 71-43-2

## Source

- https://www.cdc.gov/niosh/npg/npgd0049.html

Last verified: 2026-09-08. Review by: 2027-09-08.
Part of [US workplace chemical exposure limits: federal OSHA, Cal/OSHA and NIOSH, side by side](https://referencesource.org/workplace-exposure-limits/).