Category 1G vs 2G vs 3G: What's the Difference?
Comparison of ATEX Category 1G, Category 2G, and Category 3G equipment used in hazardous refinery environments corresponding to Zone 0, Zone 1, and Zone 2 gas atmospheres.
ATEX Categories 1G, 2G, and 3G classify equipment intended for use in potentially explosive gas atmospheres. The main difference is the level of protection provided and the conditions for which the equipment is intended.
For hazardous area engineers, the practical question is usually simple: what is the difference between 1G, 2G, and 3G, and which category is appropriate for Zone 0, Zone 1, or Zone 2?
This comparison focuses specifically on the three gas categories. For the broader ATEX category system, including dust categories 1D, 2D, and 3D, see ATEX Equipment Categories Explained.
1G vs 2G vs 3G at a Glance
| Feature | Category 1G | Category 2G | Category 3G |
|---|---|---|---|
| Protection Level | Very High | High | Normal |
| Explosive Gas Atmosphere | Present continuously, for long periods, or frequently | Likely to occur occasionally | Unlikely, or only infrequently and for a short period |
| Typical Zone Application | Zone 0 | Zone 1 | Zone 2 |
| Corresponding EPL | Ga | Gb | Gc |
| Typical Protection Approach | Very high protection against ignition | High protection against ignition | Normal protection during normal operation |
The category definitions come from Annex I of ATEX Directive 2014/34/EU. Category 1 provides a very high level of protection, Category 2 a high level, and Category 3 a normal level of protection.
What Does 1G Mean?
Category 1G is the highest ATEX equipment category for Group II equipment intended for explosive gas atmospheres.
It is designed for locations where explosive atmospheres caused by gases, vapours, or mists may be present continuously, for long periods, or frequently.
Category 1 equipment must maintain the required protection level even in the event of rare equipment-related incidents.
In hazardous area applications, Category 1G is typically associated with Zone 0.
Category 1G equipment generally corresponds to EPL Ga when the equipment marking and applicable protection concept are considered.
Typical Category 1G Applications
- Equipment installed in Zone 0
- Intrinsically safe instrumentation designed for the applicable EPL
- Gas detection and measurement equipment
- Equipment requiring very high protection against ignition
What Does 2G Mean?
Category 2G provides a high level of protection for equipment intended for explosive gas atmospheres.
It is intended for locations where an explosive atmosphere is likely to occur occasionally during normal operation.
The protection measures must continue to provide the required level of protection when frequently occurring disturbances or equipment faults that normally have to be considered are taken into account.
Category 2G is typically associated with Zone 1 and is also suitable for Zone 2 when the complete equipment requirements are satisfied.
Category 2G generally corresponds to EPL Gb.
Typical Category 2G Applications
- Ex db flameproof equipment
- Ex eb increased safety equipment
- Pressurized equipment with the applicable protection level
- Hazardous area lighting and junction boxes for Zone 1 applications
- Motors and electrical equipment certified for Category 2G
What Does 3G Mean?
Category 3G provides a normal level of protection for equipment intended for explosive gas atmospheres.
It is intended for areas where an explosive atmosphere is unlikely to occur or, if it does occur, is expected only infrequently and for a short period.
Category 3 equipment provides the required level of protection during normal operation.
Category 3G is typically associated with Zone 2.
Category 3G generally corresponds to EPL Gc.
Typical Category 3G Applications
- Ex ec electrical equipment
- Equipment certified specifically for Zone 2
- Non-sparking equipment where the applicable certification requirements are satisfied
- Electrical equipment used where explosive gas atmospheres are unlikely or short-lived
1G vs 2G vs 3G: What Is the Main Difference?
The key difference is the level of protection required for the expected presence of an explosive gas atmosphere.
| Category | Protection | Atmosphere Condition | Typical Zone | EPL |
|---|---|---|---|---|
| 1G | Very High | Continuous, long periods, or frequent | Zone 0 | Ga |
| 2G | High | Likely occasionally | Zone 1 | Gb |
| 3G | Normal | Unlikely or infrequent for a short period | Zone 2 | Gc |
The important point is that 1G, 2G, and 3G are equipment categories, while Zone 0, Zone 1, and Zone 2 are hazardous area classifications. They are related because the zone classification establishes the environmental risk, while the equipment category indicates the protection level required for equipment installed there.
Can a Higher Category Be Used in a Lower-Risk Zone?
In general, equipment providing a higher level of protection can be suitable for a lower-risk hazardous area, provided the complete equipment marking, certificate, installation requirements, and application conditions are suitable.
For example, Category 1G equipment can generally be used in Zone 1 or Zone 2, while Category 2G equipment can generally be used in Zone 2.
However, equipment selection should not be based on category alone. Gas group, temperature class, EPL, protection concept, ambient conditions, electrical parameters, and certification limitations must also be checked.
1G vs 2G vs 3G and EPL
Equipment Protection Level (EPL) is a separate classification used in the IEC 60079 framework. For gas atmospheres, the commonly corresponding protection levels are Ga, Gb, and Gc.
| ATEX Category | EPL | Typical Zone Association |
|---|---|---|
| 1G | Ga | Zone 0 |
| 2G | Gb | Zone 1 |
| 3G | Gc | Zone 2 |
This relationship is useful when reviewing equipment that carries both ATEX and IECEx-related information. EPL should nevertheless be checked together with the complete equipment marking and certification documentation.
How to Identify 1G, 2G, or 3G on Equipment
The ATEX category is normally visible in the equipment marking. For example:
II 2G Ex db IIC T6 Gb
In this example, 2G identifies the equipment as Category 2 for a gas atmosphere, while Gb identifies the associated Equipment Protection Level.
The remaining marking elements provide additional information such as the protection concept, gas group, and temperature class. Therefore, identifying the category is only the first step in verifying equipment suitability.
Common Mistakes When Comparing 1G, 2G, and 3G
Assuming 1G, 2G, and 3G Are Zone Classifications
They are not. 1G, 2G, and 3G are ATEX equipment categories. Zone 0, Zone 1, and Zone 2 classify the hazardous location.
Choosing Equipment Based Only on the Category
A correct category does not automatically mean that equipment is suitable for an installation. The complete marking and certification requirements must also be checked.
Assuming Every 2G Product Is Suitable for Every Zone 1 Application
Category 2G establishes a protection level, but the equipment must still be suitable for the specific gas group, temperature class, protection concept, ambient conditions, and other applicable requirements.
Assuming 3G Means Non-Hazardous Equipment
Category 3G equipment is still intended for potentially explosive gas atmospheres. It provides a normal level of protection and is typically associated with Zone 2 applications.
Frequently Asked Questions
What is the difference between 1G, 2G, and 3G?
1G provides a very high level of protection, 2G provides a high level of protection, and 3G provides a normal level of protection for equipment intended for explosive gas atmospheres.
Is 1G for Zone 0?
Yes. Category 1G is typically associated with Zone 0 because it is intended for areas where explosive gas atmospheres may be present continuously, for long periods, or frequently.
Is 2G for Zone 1?
Category 2G is typically associated with Zone 1 and provides a high level of protection for equipment intended for explosive gas atmospheres.
Is 3G for Zone 2?
Yes. Category 3G is typically associated with Zone 2 and provides a normal level of protection during normal operation.
Can 1G equipment be used in Zone 1?
Generally yes, provided the complete equipment certification and installation requirements are satisfied.
Does 1G always mean Ex ia?
No. Ex ia is one protection concept commonly associated with very high protection levels, but the ATEX category is determined by the complete conformity assessment and applicable protection measures.
Conclusion
The difference between ATEX Category 1G, 2G, and 3G is primarily the level of protection provided for equipment intended for explosive gas atmospheres.
1G provides a very high level of protection and is typically associated with Zone 0. 2G provides a high level of protection and is typically associated with Zone 1. 3G provides a normal level of protection and is typically associated with Zone 2.
For actual equipment selection, category should be checked together with the hazardous area classification, EPL, gas group, temperature class, protection concept, certification documentation, and installation requirements.
References
- Directive 2014/34/EU – Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres.
- IEC 60079-0 – Explosive Atmospheres – Equipment General Requirements.
- IEC 60079-14 – Explosive Atmospheres – Electrical Installations Design, Selection and Erection.
- IEC 60079 Series – Explosive Atmospheres Standards.
- European Commission ATEX Guidelines.
- IECEx Certification System Documentation.
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