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ATEX Equipment Categories Explained (1G, 2G, 3G, 1D, 2D, and 3D)

ATEX equipment categories explained. Learn 1G, 2G, 3G, 1D, 2D, and 3D classifications, hazardous area zones, and EPL mapping.
ATEX equipment categories for hazardous area electrical equipment ATEX equipment categories identify the required level of protection for equipment intended for potentially explosive atmospheres.

When selecting equipment for a hazardous area, one of the first questions is whether the equipment category matches the classified area. ATEX equipment categories provide a regulatory classification that identifies the level of protection required for equipment intended for potentially explosive atmospheres.

For equipment-group II, the categories are 1, 2, and 3. The letter following the category identifies the type of explosive atmosphere: G for gases, vapours and mists, and D for dust.

This produces the commonly encountered designations 1G, 2G, 3G, 1D, 2D, and 3D.

What Is an ATEX Equipment Category?

Under Directive 2014/34/EU, an equipment category is the classification of equipment within an equipment group that determines the level of protection that must be ensured.

For equipment-group II, which covers locations other than mines that may be endangered by explosive atmospheres, the categories are 1, 2, and 3.

The category reflects the conditions in which the equipment is intended to operate and the level of protection required against potential ignition hazards.

The basic principle is straightforward:

  • Category 1 — very high level of protection
  • Category 2 — high level of protection
  • Category 3 — normal level of protection

The lower the category number, the higher the required level of protection.

What Do the Letters G and D Mean?

The letters G and D identify the type of explosive atmosphere for which the equipment is intended.

Designation Atmosphere Typical Hazard
G Gas, vapour or mist Flammable gases, vapours and mists
D Dust Combustible dust

Therefore, 2G means Category 2 equipment intended for gas, vapour or mist atmospheres, while 2D means Category 2 equipment intended for dust atmospheres.

ATEX Categories for Gas Atmospheres

The G categories apply to equipment intended for explosive atmospheres caused by gases, vapours or mists.

Category 1G

Category 1G provides a very high level of protection. It is intended for areas where an explosive gas atmosphere is present continuously, for long periods, or frequently.

The equipment must maintain the required level of protection even in the event of rare equipment incidents.

Category 1G equipment is therefore associated with the highest-risk gas hazardous areas, typically Zone 0.

Category 2G

Category 2G provides a high level of protection. It is intended for areas where an explosive gas atmosphere is likely to occur occasionally during normal operation.

The protection must remain effective during normal operation and in the event of disturbances or equipment faults that normally have to be considered.

Category 2G equipment is typically associated with Zone 1.

Category 3G

Category 3G provides a normal level of protection. It is intended for areas where an explosive gas atmosphere is unlikely to occur or, if it occurs, is expected only infrequently and for a short period.

The required protection is provided during normal operation.

Category 3G equipment is typically associated with Zone 2.

ATEX Category Protection Level Gas Hazardous Area
1G Very High Typically Zone 0
2G High Typically Zone 1
3G Normal Typically Zone 2

The category-to-zone relationship follows the protection levels defined by the ATEX framework. Actual equipment selection must still consider the complete equipment marking, certification documentation and installation requirements.

ATEX Categories for Combustible Dust

The same category structure is used for equipment intended for explosive dust atmospheres, but the designation uses the letter D.

Category 1D

Category 1D provides a very high level of protection and is intended for areas where combustible dust atmospheres are present continuously, for long periods, or frequently.

It is typically associated with Zone 20.

Category 2D

Category 2D provides a high level of protection and is intended for areas where combustible dust atmospheres are likely to occur occasionally.

It is typically associated with Zone 21.

Category 3D

Category 3D provides a normal level of protection and is intended for areas where combustible dust atmospheres are unlikely to occur or are expected only infrequently and for a short period.

It is typically associated with Zone 22.

ATEX Category Protection Level Dust Hazardous Area
1D Very High Typically Zone 20
2D High Typically Zone 21
3D Normal Typically Zone 22

Directive 2014/34/EU defines Category 1, 2 and 3 according to the required protection level and the expected occurrence of explosive atmospheres. The same category framework covers gas, vapour, mist and air/dust mixtures, while the marking identifies the intended atmosphere using G or D.

ATEX Category vs Hazardous Area Zone

ATEX equipment categories and hazardous area zones describe related but different aspects of hazardous area engineering.

The zone describes the likelihood and duration of an explosive atmosphere being present in the location. The equipment category identifies the level of protection required from equipment intended for that environment.

Hazardous Area Atmosphere Typical ATEX Category
Zone 0 Gas 1G
Zone 1 Gas 2G
Zone 2 Gas 3G
Zone 20 Dust 1D
Zone 21 Dust 2D
Zone 22 Dust 3D

These relationships should be treated as a selection guide rather than the only criterion for equipment approval. The complete certification marking, protection concept, gas or dust group, temperature requirements, EPL, ambient conditions and certificate scope may also affect whether a particular product is suitable.

Can Higher-Category Equipment Be Used in a Lower-Risk Zone?

Generally, equipment providing a higher level of protection can be suitable for a lower-risk hazardous area, provided the complete equipment requirements are satisfied.

For example, equipment with Category 1G protection can generally provide a protection level suitable for a Zone 1 or Zone 2 application.

However, category alone does not establish complete suitability. Engineers must also verify the rest of the equipment marking and the certification conditions.

Engineering note: Do not select equipment based only on the category number. Confirm the complete Ex marking, atmosphere type, protection concept, temperature classification, EPL, certificate scope and project-specific requirements.

ATEX Categories and Equipment Protection Levels

Equipment Protection Level, or EPL, is a separate classification system used in the IEC 60079 series. EPLs are commonly encountered alongside ATEX categories on hazardous area equipment.

ATEX Category Typical EPL Relationship Protection Level
1G Ga Very High
2G Gb High
3G Gc Normal
1D Da Very High
2D Db High
3D Dc Normal

The two systems should not be treated as identical classifications. ATEX categories originate from the European regulatory framework, while EPLs are defined within the IEC 60079 hazardous area standards.

For a detailed explanation of EPLs, see: Equipment Protection Level (EPL) Explained.

How ATEX Categories Appear on Equipment Markings

The category is normally visible as part of the ATEX marking.

For example:

II 2G Ex db IIC T6 Gb

In this example, 2G identifies Category 2 equipment intended for gas, vapour or mist atmospheres.

The other elements of the marking provide additional information about the equipment group, protection concept, gas group, temperature classification and EPL.

The complete marking should therefore be evaluated rather than interpreting the category in isolation.

For a complete marking breakdown, see: How to Read ATEX Markings.

Common Mistakes When Interpreting ATEX Categories

Confusing Category with Zone

A Zone describes the hazardous location. An ATEX category describes the required protection level of equipment.

Assuming 2G Means Any Zone

Category 2G is generally associated with Zone 1 applications, but the complete equipment suitability must still be confirmed before installation.

Ignoring the G and D Designation

A category number by itself does not identify the atmosphere. 2G and 2D are different designations intended for different explosive atmospheres.

Assuming Category Alone Defines the Equipment

Two products may have the same ATEX category but different protection concepts, gas groups, temperature classes, EPLs or certification conditions.

Confusing ATEX Category with EPL

ATEX category and EPL provide related protection information but originate from different classification systems. They should not be treated as interchangeable terminology.

ATEX Category Selection Checklist

Before accepting hazardous area equipment, verify the following:

  • Is the hazardous area classified for gas or dust?
  • What hazardous area zone applies?
  • Does the equipment category correspond to the required protection level?
  • Is the G or D designation correct?
  • Does the complete Ex marking match the project requirement?
  • Is the EPL appropriate?
  • Are the gas or dust group requirements satisfied?
  • Is the temperature classification suitable?
  • Does the certificate cover the actual product and configuration?
  • Are any special conditions of use applicable?

Frequently Asked Questions

What do 1G, 2G and 3G mean?

They are ATEX equipment categories for gas, vapour and mist atmospheres. Category 1G provides a very high level of protection, 2G a high level, and 3G a normal level of protection.

What do 1D, 2D and 3D mean?

They are ATEX equipment categories for combustible dust atmospheres. Category 1D provides a very high level of protection, 2D a high level, and 3D a normal level of protection.

What is the difference between 2G and 2D?

Both are Category 2 equipment, but 2G is intended for explosive gas, vapour or mist atmospheres, while 2D is intended for combustible dust atmospheres.

Does Category 1 mean the equipment can be used everywhere?

No. A higher category does not remove the need to check the complete equipment marking, certification conditions, installation requirements and other hazardous area parameters.

Is Category 2G the same as EPL Gb?

They are closely related protection classifications, but they come from different systems. Category 2G is an ATEX designation, while Gb is an Equipment Protection Level designation used within the IEC 60079 framework.

Conclusion

ATEX equipment categories provide a practical way to identify the protection level required for equipment intended for potentially explosive atmospheres.

For equipment-group II, the three main categories are 1, 2 and 3. The letter G identifies equipment intended for gas, vapour or mist atmospheres, while D identifies equipment intended for combustible dust atmospheres.

This results in six commonly encountered designations: 1G, 2G, 3G, 1D, 2D and 3D.

Understanding these categories is an important first step in equipment selection, but category alone is not enough. The complete Ex marking, EPL, temperature classification, gas or dust group, certification documentation and installation requirements should also be checked before equipment is approved.

Engineering Reference

Directive 2014/34/EU defines equipment categories according to the required level of protection and the conditions in which explosive atmospheres may be present. For equipment-group II, Categories 1, 2 and 3 cover very high, high and normal levels of protection respectively.

Related Reading

References