IEC 60079-18 Revised
IEC 60079-18:1992
Electrical apparatus for explosive gas atmospheres - Part 18: Encapsulation 'm'
Prescribes requirements for the construction and testing of electrical apparatus, parts of electrical apparatus and Ex components which have rated voltages not exceeding 11 kV with protection encapsulation 'm'.
CHFÂ 155.-
A more recent version of this publication exists:
IEC 60079-18:2014+AMD1:2017 CSV