Defining Gas & Dust Groups, Temperature Classes and Equipment Marking

HAZOP.EU can help define the gas groups, dust groups and temperature classes associated with your dangerous substances and stipulate the required equipment markings that you require for your hazardous area zones at your facility. HAZOP.EU can either do this by analytical/calculation or by experimentation with one of our accredited testing laboratory partners.


Gas groups are generally defined by the reactivity or flammability of the gases-air mixtures in question. Flammable gas-air mixtures can also be ignited by contact with a hot surface. Consequently all electrical and non-electrical apparatus, devices and equipment must be classified according to their maximum surface temperature. HAZOP.EU uses IEC 60079-20-1 Standard, which defines the material characteristics for gas and vapour classification, test methods and associated data.

Similar to the flammable gases, dusts are defined depending on their type, flammable characteristics and reactivity. The IEC Standard that defines the material characteristics for dust classification, test methods and data is currently being developed in line with the flammable gas equivalent; IEC 60079-20-2 (IEC MT 80079-20-2 project).

Special attention has to be given to the problem of temperature limitation when dusts are involved. Dust layers display two (2) main characteristics as the thickness of the layer increases: reduction of the glow temperature and an increase in the heat insulation. Generally, this means that with increasing dust layer thickness, the dust later ignition temperatures reduces. Cloud ignition temperatures tend to be higher than dust later ignition temperatures.

If you would like to discuss in more detail HAZOP.EU Hazardous Area Classification techniques and methodologies for your operation or facility, please do not hesitate to contact HAZOP.EU for an informal, confidential conversation.