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

For Group C, category is gas group; iec / atex designation is IIB; basis or note is MESG 0.50–0.90 mm, recorded from its source on 2026-08-06.

- **Category:** gas group _(our reading, not quoted from the source)_
- **North American designation:** Group C
- **IEC / ATEX designation:** IIB _(verified: appears in the quote below)_
- **Basis or note:** MESG 0.50–0.90 mm

## What the source says

> C | IIB | Ethylene, ethyl ether | 0.50–0.90 mm

## 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.

### Basis or note

exknowledge.com says basis or note is **MESG 0.50–0.90 mm**, as of 2026-08-06.

> C | IIB | Ethylene, ethyl ether | 0.50–0.90 mm

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

ldpi-inc.com says basis or note is **Ethylene**, as of 2026-08-06.

> Ethylene | C | 450 | 842 | 1,200 PSI | IIB

Source: https://ldpi-inc.com/resources/classification-codes/class-1-locations/


## Source

- https://exknowledge.com/pages/nec-500-vs-atex-iec.html
- https://ldpi-inc.com/resources/classification-codes/class-1-locations/

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/).