Explosion-proof enclosure:

An enclosure capable of withstanding the pressure generated by an internal explosion of a specified gas and sufficiently containing such explosion to prevent ignition of an explosive atmosphere surrounding the enclosure (for Classes I, II, and I).

Oil-Immersed:

Electrical equipment is arranged so that arcing contacts, connections, etc. are immersed in oil. The arc is confined to the oil so that it will not ignite an explosive mixture of specified gases above the oil or in the atmosphere surrounding the enclosure (for Classes II, II, and I).

Purged and Pressurized Enclosure: An enclosure is protected from the accumulation of flammable gases or vapors within a container by maintaining an adequate flow of clean air or inert gas within the container (for Classes II, II, and I).

Intrinsically Safe Equipment: A conductor that is incapable of releasing sufficient electrical or thermal energy under normal and abnormal conditions to cause ignition of a specified hazardous atmospheric mixture in its most ignitable concentration (for Classes !, II, and I).

Dust-Ignition-Proof:

The enclosure is protected from the ingress of dust and the external surfaces shall not reach temperatures capable of igniting or discoloring dust on the enclosure or igniting dust-air mixtures in the surrounding atmosphere (for Class I)