Implementation
Potentially explosive areas should be divided into zones, and the equipment should be divided into groups and categories. The labelling on the identification plate of certified equipment indicates in which zone the explosion proof equipment can be used.

Division into product groups
Groups are divided into group I and group II. Group I consists of mining „underground“ and group II deals with prevention of gas and dust explosion protection for all other applications.

Division into zones
Potentially explosive areas are divided into six zones, according to time-related and local probability, that a potentially explosive atmosphere (p.e.a.) exists.
A distinction is made between combustible gases, mists, vapors and combustible dust. The zones are described in the accompanying table. Gases, mists and vapors are placed in zones 0, 1 and 2, whereby the requirements for the chosen equipment increase from zone 2 to 0. Equipment in zone 0 must be built in a way "that even if a type of protection fails or if two faults occur, that sufficient explosion protection is guaranteed". Therefore for example a passive, potential free sensor, installed in zone 0, and connected to an intrinsically safe electric circuit (II2(1)G [EExia] IIC), must display current approval. Zones 20, 21 und 22 are for dust, whereby the requirements for the chosen equipment increase from zone 22 to 20. Equipment in zone 20 and 21 need special approval.

Division into product groups
Product groups determine, in which zones the equipment should be installed. Once again there are six categories. Categories1G, 2G and 3G are classifications for gas explosion protection (G = Gas); to which equipment with 1G for zone 0, 1 and 2, equipment with 2G for zone 1 und 2 and equipment with 3G for zone 2 are suited. Categories 1D, 2D and 3D are classifications for dust explosion protection (D = Dust); to which equipment with 1D for zone 20, 21 and 22, equipment with 2D for zone 21 and 22 and equipment with 3D for zone 22 are suited.

Explosion groups, temperature classes
The equipment groups and categories determine, in which zones the equipment should be installed, therefore the explosion groups and temperature classes determine, to which mediums inside the zones, the equipment is suited. The type of protection used is not a mark of quality but is instead a constructive solution for selecting equipment for explosion protection.

Division into explosion groups
Explosion proof equipment for gases, mists and vapors is divided into three explosion groups (IIA-IIB-IIC) according to the type of protection being used. The explosion group is a means to measure the ignitability of gases (potentially explosive atmos-
pheres). The equipment requirements increase from II A to II C.

Division into temperature classes
Explosion proof equipment, installed within the Ex area, is divided into 6 temperature classes (T1 to T6). Temperature class is not – as it is often wrongly believed – the operating temperature range of the equipment, but the maximum permissible surface temperature of the equipment, in relation to + 40°C ambient temperature on any surface area, and should not be exceeded at any time. The maximum surface temperature must remain below the ignition temperature of the surroun-
ding medium at all times. The equip-
ment requirements rise from T1 to T6.