The ATEX Marking Calculator generates the correct ATEX equipment classification string from equipment group, category, protection type, gas group, and temperature class. Essential for engineers specifying equipment for hazardous areas under the EU ATEX Directive and IEC 60079 standards.
200
°C
2
1
1
0
200
°C
2
1
1
0
Specify the wrong ATEX category for a pump in a chemical plant and you risk catastrophic explosion — or face regulatory shutdown for using over-specified equipment that was never intended for the hazardous area. The calculator for ATEX marking generates the correct IEC 60079 classification string from your area classification zone and equipment parameters, ensuring compliance with the European ATEX Directive and international IEC standards for hazardous area equipment.
An ATEX mark follows a specific notation. A complete example: ⊠ II 2G Ex d IIC T4 Gb
Use this online calculator to generate the correct marking for any hazardous area classification. The IP/NEMA protection class calculator covers the complementary enclosure ingress protection standards.
The most critical matching requirement is between the hazardous area zone and equipment category:
Equipment rated for a higher-risk zone is always acceptable in a lower-risk zone — a Category 1G device can be used in Zone 0, 1, or 2. Equipment rated for a lower-risk zone must never be used in a higher-risk zone.
The temperature class (T1–T6) specifies the maximum surface temperature the equipment may reach, which must not exceed the auto-ignition temperature (AIT) of the hazardous gas or vapor:
The circuit breaker sizing calculator and protection and safety calculators provide complementary electrical safety tools.
ATEX is the European Union's hazardous area equipment directive (Directive 2014/34/EU); IECEx is the international equivalent administered by the International Electrotechnical Commission. The marking syntax is almost identical; the key difference is the certification body and geographic scope. Equipment certified to IECEx is increasingly accepted in ATEX-required markets, and dual certification (both ATEX and IECEx) is available for global deployment. Non-EU markets (US, Canada, Australia) use their own equivalent systems: NEC/NFPA 70 in the US, CEC in Canada, and AS/NZS 60079 in Australia — all technically equivalent but with different administrative requirements.
The calculator assembles the ATEX marking string using the standard format defined in IEC 60079-0:2017:
A complete ATEX marking such as II 2G Ex d IIB T4 decodes as: Group II (surface industry gas), Category 2 (Zone 1 capable), G (gas atmosphere), protection concept d (flameproof), gas group IIB (suitable for ethylene and less dangerous gases), temperature class T4 (maximum surface 135 °C). This equipment must NOT be installed in Zone 0 (category too low) and must NOT be used where gases with AIT below 135 °C are present (e.g., diethyl ether at 160 °C would require T3; carbon disulfide at 90 °C would require T6). Always match each element of the marking against the hazardous area classification and the properties of the specific flammable substance present.
Inputs
Results
Hydrogen is a Group IIC gas with auto-ignition temperature of 500 °C. A Category 2 (Zone 1) flameproof motor in IIC T1 is the appropriate specification. The T1 class permits surface temperatures up to 450 °C, safely below hydrogen's 500 °C AIT. The marking would read: II 2G Ex d IIC T1.
Inputs
Results
Aluminum dust is Group IIIC (conductive). Zone 21 requires Category 2. The 't' (dust encapsulation per IEC 60079-31) protection concept is appropriate for junction boxes. The AIT of aluminum dust cloud is approximately 590 °C, but the minimum ignition temperature of a layer is only 320 °C — the T4 (135 °C) class provides a generous safety margin against layer ignition. Marking: II 2D Ex t IIIC T4.
ATEX is the European Union regulatory scheme, mandatory for equipment placed on the EU market, governed by Directive 2014/34/EU. IECEx is the international certification scheme administered by the IEC, recognized in over 50 countries but not legally mandatory in those countries — local regulations may require national certification. The technical standards (IEC 60079 series) are identical; the marking format is nearly the same (IECEx uses the Ex mark rather than ATEX's hexagonal mark). Equipment often carries both certifications.
No. Zone 0 (or Zone 20 for dust) requires Category 1 equipment, which must remain safe even with two rare independent faults. Category 2 equipment is designed for Zone 1/21 and is only required to be safe with one frequently occurring fault. Using Category 2 equipment in Zone 0 is a violation of ATEX Directive 2014/34/EU and creates an unacceptable safety risk.
The gas group reflects the ignition hazard of the specific flammable substance. IIC equipment (the highest group, covering hydrogen and acetylene) is certified to be safe in the most easily ignited atmospheres and will also be safe in IIA and IIB environments. IIA equipment (propane, methane) cannot be used where IIB or IIC gases are present. Always match or exceed the gas group of the substance present. Over-specifying (e.g., using IIC equipment in a propane environment) is safe but may be unnecessarily costly.
The auto-ignition temperature (AIT) is the minimum temperature at which a flammable substance will spontaneously ignite without an external ignition source. The equipment temperature class must ensure that the surface temperature of the equipment never reaches the AIT. The required T-class is determined by: find the AIT of the gas; select the T-class whose maximum temperature is below the AIT with a suitable safety margin (typically at least 50 °C below AIT for gases, per EN 13463-1). For example, diethyl ether AIT = 160 °C → T4 (max 135 °C) is required; petrol/gasoline AIT ≈ 280 °C → T3 (max 200 °C) is adequate.
Yes, but Zone 2 allows Category 3 equipment, which is the least restrictive ATEX category. Zone 2 is characterized by explosive atmospheres that are unlikely to occur in normal operation and, if they do, persist only for short periods (typically defined as less than 10 hours per year). Category 3 equipment must be safe during normal operation but is not required to maintain safety during a fault condition.
Intrinsic safety (IS) limits the electrical energy in a circuit — both under normal conditions and under specified fault conditions — to below the minimum ignition energy of the surrounding atmosphere. IS circuits require specially certified barriers or galvanic isolators (Zener barriers or galvanic isolators) at the safe area/hazardous area boundary. IS is preferred for instrumentation and field devices (sensors, transmitters, solenoid valves) because IS equipment can be maintained and adjusted live in the hazardous area, significantly reducing maintenance downtime. 'ia' provides Category 1 protection (Zone 0 capable); 'ib' provides Category 2; 'ic' provides Category 3.
ATEX Directive 2014/34/EU covers both electrical and non-electrical (mechanical) equipment. Non-electrical equipment can generate ignition sources through friction, impact sparks, static electricity, and hot surfaces. Non-electrical equipment follows the same group and category structure but uses protection concepts defined in EN 13463 series (e.g., flow restriction 'fr', constructional safety 'c', control of ignition sources 'b'). This is an area often overlooked — mechanical equipment such as fans, conveyors, and couplings in explosive atmospheres must also carry ATEX certification.
ATEX Directive 1999/92/EC (the Workplace Directive, now consolidated into Directive 2014/34/EU for the equipment side and remaining separately for the workplace side) requires employers to produce an Explosion Protection Document (EPD) that includes: hazardous area classification drawings, equipment register with ATEX certificate numbers, inspection and maintenance schedules, and risk assessment documentation. The EPD must be drawn up before work in the hazardous area begins and reviewed whenever the installation, processes, or substances change.
How helpful was this calculator?
Be the first to rate!
