An ATEX marking tells you exactly where and how a piece of equipment can be used in explosive atmospheres. Reading left to right, it identifies: the CE mark and notified body number, the ATEX "epsilon-x" hexagon, the equipment group (I for mines, II for surface), the category (1-3 for surface equipment), the atmosphere type (G for gas, D for dust), then the specific explosion protection details (type of protection, gas group, temperature class).
What ATEX means
ATEX comes from the French "ATmospheres EXplosibles." It refers to two EU directives:
- Directive 2014/34/EU (the "ATEX Equipment Directive"): covers equipment and protective systems intended for use in potentially explosive atmospheres. This is the directive that creates the marking requirements.
- Directive 1999/92/EC (the "ATEX Workplace Directive"): covers the safety of workers in explosive atmospheres. This directive classifies hazardous areas into zones.
Every piece of electrical equipment installed in a classified hazardous area in the EU must carry an ATEX marking demonstrating compliance with 2014/34/EU. The marking is the proof that the equipment has been designed, tested, and certified for use in that environment.
Breaking down a real marking
Let's decode a complete ATEX marking for a junction box suitable for use in gas zones:
CE 0080 [Ex hexagon] II 2 G Ex db IIC T6 Gb
Each component means something specific:
Component 1: CE mark and notified body
CE 0080
- CE: The product complies with applicable EU directives.
- 0080: The four-digit number identifies the notified body (third-party certification laboratory) that performed the conformity assessment. In this case, 0080 is the number for a specific EU notified body. Common notified bodies include DEKRA (0158), BASEEFA (0600), and INERIS (0080).
Component 2: The ATEX hexagon symbol
[Ex hexagon]
The distinctive hexagonal symbol containing "Ex" (epsilon-x) indicates the product is certified under the ATEX Equipment Directive. In text, this is often represented as a hexagon with Ex inside, or simply written as the Ex mark. On physical products, it is a standardized pictogram.
Component 3: Equipment group
II
| Group | Application |
|---|---|
| I | Equipment for use in underground mines (firedamp and combustible dust) |
| II | Equipment for use in all other potentially explosive atmospheres (surface industries) |
Group II covers the vast majority of electrical equipment in petrochemical, pharmaceutical, food processing, and industrial applications. Group I is specific to coal and other underground mines where methane (firedamp) is present.
Component 4: Equipment category
2
For Group II equipment, the category indicates the protection level:
| Category | Protection level | Zone applicability (gas) | Zone applicability (dust) |
|---|---|---|---|
| 1 | Very high protection | Zone 0 (continuous/long periods) | Zone 20 |
| 2 | High protection | Zone 1 (likely to occur occasionally) | Zone 21 |
| 3 | Normal protection | Zone 2 (unlikely, short duration) | Zone 22 |
Category 2 equipment can be used in Zone 1 and Zone 2 gas areas, or Zone 21 and Zone 22 dust areas. Category 1 equipment can be used in all zones including the most hazardous (Zone 0/20).
Component 5: Atmosphere type
G
| Letter | Atmosphere |
|---|---|
| G | Gas, vapor, or mist |
| D | Dust |
Equipment marked "G" is certified for gaseous explosive atmospheres. Equipment marked "D" is certified for combustible dust atmospheres. Some equipment carries both: "GD" means certified for both gas and dust environments.
Component 6: Type of protection
Ex db
The "Ex" prefix followed by one or two lowercase letters identifies the explosion protection concept used. Common types:
| Code | Protection concept | Principle |
|---|---|---|
| d | Flameproof enclosure | Enclosure contains the explosion; gaps are too narrow for flame to propagate |
| e | Increased safety | Extra measures prevent sparks, arcs, and hot surfaces |
| i (ia, ib, ic) | Intrinsic safety | Energy limited so no ignition is possible |
| p (px, py, pz) | Pressurized enclosure | Internal overpressure prevents explosive atmosphere from entering |
| m (ma, mb) | Encapsulation | Potential ignition sources sealed in compound |
| n (nA, nC, nR) | Non-sparking | Equipment does not produce sparks in normal operation |
| t (ta, tb, tc) | Protection by enclosure (dust) | Enclosure prevents dust ingress |
| o | Oil immersion | Potential ignition sources submerged in oil |
| q | Powder/sand filling | Enclosure filled with granular material |
The suffix letter (a, b, c) after the protection type indicates the Equipment Protection Level (EPL):
- a: Highest level ("Ga" for gas, "Da" for dust)
- b: Normal level ("Gb" for gas, "Db" for dust)
- c: Basic level ("Gc" for gas, "Dc" for dust)
In our example, "db" means flameproof enclosure with normal protection level (Gb).
Component 7: Gas group
IIC
For gas atmospheres, the gas group indicates which gases the equipment is certified for:
| Group | Representative gas | Ignition energy |
|---|---|---|
| IIA | Propane | Highest (easiest to protect against) |
| IIB | Ethylene | Medium |
| IIC | Hydrogen, acetylene | Lowest (hardest to protect against) |
IIC certification covers all gas groups (IIA, IIB, and IIC). IIB covers IIA and IIB. IIA covers only IIA. Equipment certified for IIC is the most versatile.
Component 8: Temperature class
T6
The temperature class indicates the maximum surface temperature of the equipment during operation:
| Class | Maximum surface temperature |
|---|---|
| T1 | 450 degrees C |
| T2 | 300 degrees C |
| T3 | 200 degrees C |
| T4 | 135 degrees C |
| T5 | 100 degrees C |
| T6 | 85 degrees C |
T6 is the most restrictive (lowest surface temperature). The temperature class must be lower than the auto-ignition temperature of the gas present in the installation. Hydrogen has an auto-ignition temperature of 560 degrees C, so T1 through T6 all work. Carbon disulfide has an auto-ignition temperature of 95 degrees C, requiring T6 (85 degrees C maximum).
Component 9: Equipment Protection Level (EPL)
Gb
The final element confirms the Equipment Protection Level:
| EPL | Gas | Dust | Meaning |
|---|---|---|---|
| Ga / Da | Zone 0 / Zone 20 | Zone 20 | Very high, two independent means of protection |
| Gb / Db | Zone 1 / Zone 21 | Zone 21 | High, functions safely with one recognized fault |
| Gc / Dc | Zone 2 / Zone 22 | Zone 22 | Enhanced, functions safely in normal operation |
Complete worked example
Let's read a complete marking for an LED luminaire used in a petrochemical plant:
CE 0158 [Ex hexagon] II 2 GD Ex db eb IIC T4 Gb
Ex tb IIIC T80°C Db
This luminaire has dual certification:
For gas: Ex db eb IIC T4 Gb
- Flameproof enclosure (db) combined with increased safety (eb)
- All gas groups (IIC)
- Maximum surface temperature 135 degrees C (T4)
- Equipment Protection Level Gb (suitable for Zone 1 and Zone 2)
For dust: Ex tb IIIC T80°C Db
- Protection by enclosure (tb)
- All dust groups (IIIC: conductive dust)
- Maximum surface temperature 80 degrees C
- Equipment Protection Level Db (suitable for Zone 21 and Zone 22)
ATEX markings in product data
ATEX marking is one of the most complex structured attributes in electrical product data. Storing it as a single free-text field makes it unfilterable and unsearchable. Best practice is to decompose the marking into its constituent parts:
atex_group: "II"
atex_category: "2"
atex_atmosphere: "GD"
atex_protection_type: "db eb"
atex_gas_group: "IIC"
atex_temperature_class: "T4"
atex_epl: "Gb"
atex_full_marking: "Ex db eb IIC T4 Gb / Ex tb IIIC T80°C Db"
This enables faceted search: "Show me all Zone 1 luminaires for IIC gases with T4 or better."
Validate ATEX markings with the free ATEX marking validator. It parses the marking components and checks that the combination of protection type, gas group, and temperature class is consistent.
When building product catalogs for hazardous area equipment, getting the ATEX marking exactly right is not just a data quality issue. It is a safety and legal requirement. An incorrect marking on a data sheet could lead to equipment being installed in a zone it is not rated for. Validate every marking with the ATEX marking validator before publishing.