ATEX equipment is divided into groups based on the intended environment of use. This fundamental classification determines the applicable Essential Health and Safety Requirements (EHSRs), conformity assessment routes, and marking requirements under Directive 2014/34/EU.

Group I - Mining Applications

Group I covers equipment intended for use in underground parts of mines and surface installations of mines endangered by firedamp and/or combustible dust.

• Primary hazards: Firedamp (methane from coal seams, typically 80-95% CH₄) and coal dust (explosive concentration 40-50 g/m³, MIE 40-60 mJ)
• Categories: M1 (very high protection, can remain energised during explosive atmosphere) and M2 (high protection, de-energised when explosive atmosphere detected)
• Special requirements: Enhanced mechanical strength, flame propagation resistance for cables, specific tests for coal dust ignition
• Market share: Approximately 2-3% of total ATEX certified equipment

Group I equipment must meet the specific EHSRs in Directive 2014/34/EU Annex II Section 2.0. Mining environments present unique challenges including limited ventilation, water ingress, mechanical damage from operations, and the constant presence of methane in coal seams.

Group II - Surface Industries

Group II covers equipment intended for use in other places liable to be endangered by explosive atmospheres—essentially all non-mining applications. This group represents approximately 97% of ATEX certified equipment.

• Subdivisions: IIA for typical industrial gases (propane, methane—MESG above 0.9mm), IIB for more easily ignited gases (ethylene, hydrogen sulphide—MESG 0.5-0.9mm), IIC for the most easily ignited gases (hydrogen, acetylene—MESG below 0.5mm)
• Categories: 1 (very high protection for Zone 0/20), 2 (high protection for Zone 1/21), 3 (normal protection for Zone 2/22)
• Industries: Oil and gas, chemical, pharmaceutical, food processing, surface coating, waste treatment, and many more

Equipment marked IIC is suitable for all Group II atmospheres. Equipment marked IIB is suitable for IIB and IIA atmospheres. Equipment marked IIA is only suitable for IIA atmospheres. The hierarchy reflects the decreasing hazard level from hydrogen/acetylene through to propane-type gases.

Group III - Dust Atmospheres

Since the EN 60079-0:2012 standard, Group III has been formally recognised for non-mining dust atmospheres. The subdivisions are IIIA for combustible flyings (fibres, lint), IIIB for non-conductive dusts (grain, plastic), and IIIC for conductive dusts (metal powders, carbon).

Conductive dusts (Group IIIC) present the greatest hazard due to their ability to form conductive paths and lower MIE values. Aluminium powder has MIE as low as 10-50 mJ, compared to 1000+ mJ for some organic dusts.

Marking Format

Equipment marking indicates the group using standardised notation. Group I equipment shows "I M1" or "I M2" indicating mining equipment and category. Group II equipment shows "II 2 G" for Category 2 gas equipment or "II 3 D" for Category 3 dust equipment. Combined gas and dust equipment shows "II 2 GD" indicating suitability for both atmospheres.

a mining approved thermal camera with II 2G rating

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Selection Considerations

When selecting equipment, always verify the equipment group matches your application. Group I equipment can only be used in mining applications—do not use in surface industries even if the protection type appears suitable. Group II equipment should not be used underground. Within Group II, verify the gas group subdivision (IIA, IIB, or IIC) is appropriate for all substances that may be present in your classified area. Temperature class must also be verified independently of equipment group.