# Group B — North American vs IEC/ATEX explosion protection designations

For Group B, category is gas group; iec / atex designation is IIC (partially IIB+H₂); basis or note is MESG <0.50 mm, recorded from its source on 2026-08-06.

- **Category:** gas group _(our reading, not quoted from the source)_
- **North American designation:** Group B
- **IEC / ATEX designation:** IIC (partially IIB+H₂) _(verified: appears in the quote below)_
- **Basis or note:** MESG <0.50 mm

## 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: 2026-08-06. Review by: 2028-08-05.
Part of [North American vs IEC/ATEX explosion protection designations](https://referencesource.org/ex-classification-system-crosswalk/).