CENELEC

Type “d” (EExd):  Explosionproof/Flameproof Enclosure.  An enclosure that can withstand the pressure developed during an internal explosion of specified gases and which prevents the transmission of the explosion to the explosive atmosphere surrounding the enclosure (for Zones 1 and 2).

Type “o” (EExo):  Oil immersion.  The electrical apparatus is immersed in oil in such a way that an explosive atmosphere, which may be above the oil or outside the enclosure  cannot be ignited (for Zone 2).

Type “p” (EExp):  Pressurized enclosure.  The entry of a surrounding atmosphere into the enclosure is prevented by maintaining inside the enclosure a protective gas at a higher pressure than that of the surrounding atmosphere (for Zones 1 and 2).

Type “i” (EExi):  Intrinsically Safe Systems are incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause and ignition of a given explosive atmosphere  (for all Zones, 0, 1 and 2).

Type “e” (EExe):  Increased Safety.  Measures are taken to prevent, with a minor degree of security, the possibility of excessive temperatures and the occurrence of arcs or sparks in the interior and on the external parts of the electrical apparatus which do not them in normal service (for Zones 1 and 2).

Type “g” (EExg):   Powder filled.  The enclosure is filled with finely granulated material such that, in the intended service conditions, any arc occurring within the enclosure of an electrical apparatus will not ignite the surrounding atmosphere.  No ignition shall be caused by flame or excessive temperature of the surfaces of the enclosure (for Zone 2).

Type “N” (Exn):  Not CENELEC recognized.  Measures are applied to the electrical apparatus such that, in normal operation, it is not capable of igniting a surrounding explosive atmosphere and a fault capable of causing ignition is not likely to occur (for Zone 2).

NEC

Explosion-Proof Enclosure:  An enclosure which can withstand the pressures resulting from an internal explosion of specified gases, and contain such an explosion sufficiently to prevent the ignition of the explosive atmosphere surrounding the enclosure (for Class I, II and III).

Oil Immersion:  The electrical apparatus’ are arranged such that the arcing contacts, connections, etc., are immersed in oil.  Arcing is confined under the oil such that it will not ignite an explosive mixture of specified gases above the oil or in the atmosphere surrounding the enclosure (for Class I, II and III).

Purged & Pressurized Enclosures:  The accumulation of ignitable gases or vapors in the enclosure is prevented by maintaining, inside the enclosure, sufficient flow of clean air or inert gas (for Class I, II and III).

Intrinsically Safe Equipment:  Wiring that is incapable of releasing sufficient electrical or thermal energy, under normal and abnormal conditions, to cause ignition of a specific hazardous atmospheric mixture in its most easily ignitable concentration (for Class I, II and III).

Dust Ignition-Proof:  The enclosure prevents the entrance of dust, and external surfaces shall not reach temperatures capable of igniting or discoloring dust on the enclosure or igniting dust-air mixtures in the surrounding atmospheres (for Class II).