Atmospheric Groups

Currently there are 2 material groups, namely: material group I and II:

     – Equipment group I concerns all underground installations (mining)

     – Equipment group II covers all other above-ground installations


ATEX defines gas groups based on flame or spark ignition. Distinction between gas groups are established according to MSEG (maximum experimental safe gaps) and MIE (minimum Ignition Energy), thus range of explosive concentrations and self-ignition temperature.   

These are the gas groups and the most common gases in each group:

       IIA             butane, propane, kerosene, acetone, petroleum fuel, ammonia, ethane, methanol, carbon monoxide, ethanol, diesel fuel, avgas fuel, ethyl nitrite

       IIB             ethylene, hydrogen sulphide, ethyl oxide, coal gas

       IIC             acetylene, hydrogen, carbon disulphide


As more and more European Standards are based on IEC (International Electrotechnical Commission), we also deal with new dust-groups within Europe. The dust-groups are subdivided into three categories:

       IIIA           Grain dust (dust particles larger than 0,5 mm)

       IIIB           Coal dust (dust particles smaller than 0,5 mm)

       IIIC           Metal dust (conductive dust)