From the marking on the attached data sheet, this is an Ex "e " empty enclosure (Incresed safety) and is allowed in Zone 1 and 2 (EPL Gb) for all gas groups.

This is not a "button".

Ex e achieves safety by not producing sparks, like fixed terminals, a button would produce a short circuit every time it is pushed.

You can also se that this is a "Component" since it has a "U" at the end of the certificate number, and therefore no T-Class. So it is not allowed to be installed without a complete certificate.

The IECEx certificate from your datasheet can be downloaded here: https://www.iecex-certs.com/#/...

Buttons or switches in such encloseures are usually either "Ex db eb" or part of an intrinsic safe circuit.

But the combination of an enclosure and a button must have a complete "Ex equipment" certification.