# B — Certification marks and hazardous-area classifications: cross-market equivalences

For B, stated equivalent is IIC (partially IIB+H₂); applies to is Hydrogen, butadiene, verified against its source on 2026-08-11.

- **Designation:** B _(verified: appears in the quote below)_
- **Stated equivalent:** IIC (partially IIB+H₂) _(verified: appears in the quote below)_
- **Applies to:** Hydrogen, butadiene _(verified: appears in the quote below)_

## What the source says

> B | IIC (partially IIB+H₂) | Hydrogen, butadiene | <0.50 mm

## Source

- https://exknowledge.com/pages/nec-500-vs-atex-iec.html

Last verified: 2026-08-11. Review by: 2027-08-11.
Part of [Certification marks and hazardous-area classifications: cross-market equivalences](https://referencesource.org/certification-standards-equivalence/).