Matching ATEX Equipment to Hazardous Zones | Atexshop

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Selecting the right equipment for hazardous areas isn't guesswork—the ATEX Workplace Directive specifies exactly which equipment categories are permitted in each zone. Getting this wrong can have serious consequences: using equipment with insufficient protection may cause ignition, while over-specifying drives up costs unnecessarily.

The Basic Rule

Annex II Part B of Directive 1999/92/EC establishes minimum requirements for equipment selection based on zone classification. The principle is straightforward: more hazardous zones require higher category equipment. Higher categories can always substitute for lower ones, but never the reverse.

Gas and Vapour Atmospheres

For areas classified according to gas, vapour, or mist hazards:

Zone 0: Category 1G equipment only
Zone 1: Category 1G or 2G equipment
Zone 2: Category 1G, 2G, or 3G equipment

Dust Atmospheres

For areas classified according to combustible dust hazards:

Zone 20: Category 1D equipment only
Zone 21: Category 1D or 2D equipment
Zone 22: Category 1D, 2D, or 3D equipment

Beyond Category: Other Matching Requirements

Selecting by category alone isn't sufficient. Equipment must also be suitable for the specific substances present:

Gas Group: Equipment certified for Group IIA gases (like propane) cannot be used where Group IIC gases (like hydrogen) are present. IIC equipment is suitable for all Group II gases; IIB is suitable for IIA and IIB; IIA is suitable only for IIA atmospheres.

Temperature Class: The equipment's temperature class must ensure maximum surface temperature stays below the auto-ignition temperature of substances present, with appropriate safety margins. T6 equipment (max 85°C) is suitable for all substances; T1 (max 450°C) has the most limited application.

Dust Temperature: For dust atmospheres, maximum surface temperature must be below both the dust cloud ignition temperature and the dust layer ignition temperature (with specific calculation rules).

Dual-Classified Areas

Some areas contain both gas and dust hazards—for example, a coal handling facility with methane and coal dust. Equipment must be suitable for both hazards. A motor marked "II 2 G" (gas only) cannot be used even if the gas hazard is the dominant risk. Equipment marked "II 2 GD" addresses both.

Equipment Already in Service

The Workplace Directive includes transitional provisions for existing equipment. Equipment already in use before 30 June 2003 (the transposition deadline) could continue if selected based on adequate risk assessment. However, any new equipment, or replacement for failed equipment, must comply with current requirements.

Documentation Requirements

Equipment selection must be documented in the Explosion Protection Document. For each item of equipment in hazardous areas, records should show: the zone it's installed in, the equipment category and marking, why it's suitable for substances present (gas group, dust group, temperature), and evidence of proper installation and maintenance.

Common Selection Errors

Frequent mistakes include using Category 3 equipment in Zone 1 areas (especially for "temporary" installations), ignoring gas group or temperature requirements (correct category but wrong gas group), failing to consider dust layer temperatures, and not accounting for process changes that alter the hazardous substances present.