Selection of Apparatus According to Gas grouping

  1. European standards or IEC

    Group 1:	For coal mining (methane)
    Group II:	For gases and vapors encountered in the surface industries.
    Sub groups:	II A (Propane)
    		II B (Ethylene)
    		II C (Hydrogen)
  2. NEC groups

    D (Propane), C (ethylene), B (Hydrogen), A (Acetylene)

The danger of gas increases from explosion group IIA to IIC according to IEC and from Group D to Group A to the NEC classifications. The requirements for electrical apparatus for these groups increase accordingly. Electrical apparatus certified for IIC for example is suitable for all other explosion group.