NEC Enclosure Classifications

Explosion-proof enclosure: An enclosure capable of withstanding the pressure generated by an internal explosion of a specified gas and of controlling the explosion sufficiently to prevent ignition of an explosive atmosphere surrounding the enclosure (for Classes I, II, and III).

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

Purged and Pressurized Enclosure: An enclosure that prevents the accumulation of flammable gases or vapors within the enclosure by maintaining an adequate flow of clean air or inert gas inside the enclosure (for Classes I, II, and III).

Intrinsically Safe Equipment: A circuit that, under normal and abnormal conditions, does not release sufficient electrical or thermal energy to cause ignition of a specified hazardous atmospheric mixture in the most ignitable concentration (for Classes I, II, and III).

Dust-Ignition-Proof: An enclosure that prevents the ingress of dust and whose external surfaces shall not reach temperatures that would ignite or discolor dust on the enclosure or ignite a dust-air mixture in the surrounding atmosphere (for Class II).

ATEX Enclosure Classifications

Type "d" (Exd): Explosion/flameproof enclosure. This enclosure withstands the pressure generated by an explosion of a specified gas inside and prevents the explosion from spreading to the explosive atmosphere around the enclosure (for Zones 1 and 2).

Type "o" (Exo): Oil immersed. The electrical equipment is immersed in oil so that explosive gases above the oil or outside the enclosure cannot be ignited (for Zone 1).

Type "p" (Exp): Pressurized enclosure. The surrounding atmosphere is prevented from entering the enclosure by maintaining a shielding gas at a higher pressure inside the enclosure than the surrounding atmosphere (for Zones 1 and 2).

Type "i" (Exi): Intrinsically safe systems cannot release sufficient electrical or thermal energy to cause and ignite a specified explosive atmosphere under normal or abnormal conditions (for all zones 0, 1 and 2).

Type "e" (Exe): Enhanced safety. Measures are taken to prevent, under reduced conditions of safety, the possibility of excessive temperatures and arcs or sparks inside and outside the electrical equipment which cannot occur in normal use (applicable to Zones 1 and 2).

Type "q" (Exq): Powder filling. The enclosure is filled with fine granular material so that any arc occurring inside the enclosure of the electrical equipment cannot ignite the surrounding air under the conditions of intended use. Flames or excessive temperatures on the surface of the enclosure cannot cause any ignition (applicable to Zone 1).

Type "N" (Exn): Not approved by CENELEC. Measures are taken for electrical equipment so that in normal operation it cannot ignite the surrounding explosive atmosphere and a fault that could lead to ignition is unlikely (applicable to Zone 2).