ATEX Standard Explosion-proof Enclosure Classifications

Type “d” (Ex d): Explosion-proof / 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” (Ex o): 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 1).

Type “p” (Ex p): 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” (Ex i): Intrinsically Safe

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” (Ex e): 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 occur in normal service (for Zones 1 and 2).

Type “q” (Ex q): 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 1).

Type “N” (Ex n): 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).