Decoding ATEX Markings: How to Read Equipment Rating Plates
Learn how to read and understand ATEX markings on equipment. This guide explains every element of ATEX rating plates so you can verify equipment suitability for your hazardous areas.
Why ATEX Markings Matter
Every piece of ATEX-certified equipment carries markings that tell you exactly where and how it can be safely used. These markings aren't optional labels—they're legally required identifications that specify the equipment's certified protection level, suitable zones, and operating limitations.
Understanding these markings is essential. Using equipment outside its certified parameters violates DSEAR regulations and creates genuine explosion risk. If an incident occurs and the equipment wasn't suitable for the zone classification, the consequences extend beyond the immediate harm to include regulatory enforcement and potential prosecution. [LINK: DSEAR Compliance Guide]
This guide explains how to read ATEX marking plates so you can verify equipment suitability and make informed purchasing decisions.
The ATEX Symbol and CE/UKCA Marking
ATEX equipment displays the distinctive 'Ex' marking inside a hexagon—the international symbol for explosion-protected equipment. This symbol indicates that the equipment has been assessed and certified for use in potentially explosive atmospheres. [LINK: What is ATEX?]
In Europe, ATEX equipment also carries the CE marking, indicating conformity with the ATEX Directive (2014/34/EU). In the UK following Brexit, equipment may carry either CE marking (still accepted) or the UKCA marking for equipment certified to UK regulations.
Alongside these symbols, you'll find a four-digit number identifying the Notified Body (for CE marking) or Approved Body (for UKCA marking) that certified the equipment. This provides traceability to the certification.
Equipment Groups: I, II, and III
ATEX equipment is classified into groups based on where it's intended to be used:
Group I: Equipment for underground mines and their surface installations where firedamp (methane) and/or combustible dust may be present. This is specialised mining equipment and is rarely encountered outside that sector.
Group II: Equipment for surface industries with explosive gas atmospheres. This is further subdivided into gas groups (IIA, IIB, IIC) based on the ignition energy and maximum experimental safe gap of the gases involved. IIC is the most stringent, covering hydrogen and acetylene.
Group III: Equipment for surface industries with explosive dust atmospheres. This is subdivided into IIIA (combustible flyings), IIIB (non-conductive dusts), and IIIC (conductive dusts). IIIC is the most stringent.
For industrial vacuums handling combustible dusts, you'll typically be looking at Group III equipment. For environments with flammable gases or vapours, Group II applies. Some equipment is certified for both.
Equipment Categories: 1, 2, and 3
The category indicates the protection level and determines which zones the equipment can be used in: [LINK: ATEX Zone Classifications Explained]
Category 1: Very high protection level. Equipment remains safe even with two independent faults. Suitable for Zone 0/20 (and all less hazardous zones).
Category 2: High protection level. Equipment remains safe with one fault. Suitable for Zone 1/21 (and Zone 2/22).
Category 3: Normal protection level. Equipment provides protection during normal operation. Suitable for Zone 2/22 only.
The category is followed by G (for gas atmospheres), D (for dust atmospheres), or both. For example, Category 2D indicates equipment suitable for Zone 21 and Zone 22 dust atmospheres.
Protection Concepts (Ex Codes)
The marking includes codes indicating how the equipment achieves explosion protection. Common protection concepts include:
For gas atmospheres:
Ex d — Flameproof enclosure (contains any internal explosion)
Ex e — Increased safety (prevents sparks and hot surfaces)
Ex i — Intrinsic safety (limits energy below ignition level)
Ex p — Pressurised enclosure (maintains overpressure with clean air)
Ex n — Non-sparking (for Zone 2 only)
For dust atmospheres:
Ex t — Protection by enclosure (prevents dust ingress)
Ex ia/ib — Intrinsic safety (limits energy)
Equipment may combine multiple protection concepts for different components—for example, a flameproof motor (Ex d) with increased safety terminals (Ex e).
Temperature Class and Maximum Surface Temperature
For gas atmospheres, temperature classes indicate the maximum surface temperature of the equipment:
T1: ≤450°C
T2: ≤300°C
T3: ≤200°C
T4: ≤135°C
T5: ≤100°C
T6: ≤85°C
The equipment temperature class must be lower than the auto-ignition temperature of any gases present.
For dust atmospheres, the marking shows the maximum surface temperature directly (e.g., T125°C), which must be below both the dust cloud ignition temperature and the dust layer ignition temperature (with appropriate margins).
Reading a Complete ATEX Marking
Let's decode a typical ATEX marking for an industrial vacuum:
Example: II 2D Ex h tb IIIC T125°C Db
II — Group II (surface industries), not mining
2D — Category 2 for Dust atmospheres (suitable for Zone 21 and 22)
Ex h — Explosion protection using multiple methods
tb — Protection by enclosure, level 'b' (for Zone 21
IIIC — Suitable for conductive dusts (most stringent dust group)
T125°C — Maximum surface temperature of 125°C
Db — Equipment Protection Level for dust, 'b' level
This equipment can be used in Zone 21 and Zone 22 areas with any type of combustible dust, provided the dust's minimum ignition temperature exceeds 125°C (for cloud) or is appropriately higher for layers.
Verifying Equipment Suitability
Before using any equipment in a hazardous area, verify:
The equipment category matches or exceeds your zone classification requirement
The equipment group (G for gas, D for dust) matches your hazard type
The gas/dust group is appropriate for your specific substances
The temperature class/maximum surface temperature is suitable
The equipment has valid certification documentation
If you're uncertain about any aspect of equipment suitability, seek expert advice before use. The consequences of using incorrectly rated equipment are too serious to risk.
Expert ATEX Equipment Guidance
CFM North East can help you understand equipment markings and select correctly rated vacuums for your zone classifications. Our team has extensive experience matching ATEX equipment to specific applications. [LINK: ATEX Vacuum Buying Guide]
