ATEX is the set of European Union directives that govern equipment and work in potentially explosive atmospheres. The name comes from the French Atmospheres Explosibles, and for an engineer it answers a legal question: is this device permitted to be installed in a European hazardous area, and in which zone? This guide explains how ATEX works and where it fits in oil and gas.
ATEX in one line: ATEX refers to two EU directives on explosive atmospheres. The equipment directive 2014/34/EU governs the design and certification of equipment intended for use in explosive atmospheres, and the workplace directive 1999/92/EC covers employer duties to protect workers. ATEX classifies areas into zones and assigns equipment to categories that match those zones, using protection methods such as flameproof, intrinsic safety, and pressurization.
ATEX is not a single rule but two complementary EU directives. Directive 2014/34/EU (the equipment or product directive) sets the requirements manufacturers must meet before placing equipment intended for explosive atmospheres on the European market, including design, certification, and CE and Ex marking. Directive 1999/92/EC (the workplace or social directive) places duties on employers to assess explosion risk, classify their hazardous areas, and select suitable equipment.
Together they close the loop: the product directive ensures a device is built and certified for its intended zone, and the workplace directive ensures the operator installs only equipment appropriate to the zone they have classified. In the EU, using non-ATEX equipment in a classified area is a legal, not just a technical, failure.
ATEX uses the international zone system: Zones 0, 1, and 2 for gases and vapors (present continuously, likely, or rarely, respectively) and Zones 20, 21, and 22 for combustible dusts. Equipment is divided into Group I (mining) and Group II (surface industry, including oil and gas), and Group II is further split into gas subgroups IIA, IIB, and IIC by ignition sensitivity, with a temperature class T1 to T6 limiting maximum surface temperature.
Each device carries an equipment category that maps to the zones it may enter. Category 1 equipment is suitable for Zone 0, Category 2 for Zone 1, and Category 3 for Zone 2, with the higher categories offering more protection and redundancy. The Ex marking spells out the protection concept used, such as Ex d (flameproof), Ex i (intrinsic safety), Ex e (increased safety), or Ex p (pressurization).
For any oil and gas facility built, operated, or supplied within the European Union and much of the wider European market, ATEX is the framework that decides which instruments, motors, junction boxes, and electronics can be installed near hydrocarbons. A field transmitter destined for a European gas plant must carry an appropriate ATEX category, gas group, and temperature class for the zone it will occupy.
ATEX is closely aligned with the international IECEx scheme, which uses the same zones, protection concepts, and Ex markings. Many manufacturers certify to both so a single product can be sold globally. The practical difference is legal reach: ATEX is the EU regulatory instrument required for the European market, while IECEx is a voluntary international certification system that many countries accept or reference.
ATEX is EU law: directive 2014/34/EU legally requires appropriate certification and CE and Ex marking before equipment for explosive atmospheres can be placed on the European market. IECEx is a voluntary international certification scheme run under IEC that uses the same zones, protection concepts, and Ex markings. They are technically harmonized, so equipment is often dual-certified, but ATEX is a regional legal requirement while IECEx is an international acceptance framework.
For gas atmospheres, Category 1 equipment is permitted in Zone 0 (explosive atmosphere present continuously or for long periods), Category 2 in Zone 1 (likely to occur in normal operation), and Category 3 in Zone 2 (unlikely, and only for a short period). Higher categories provide more protection and redundancy, and equipment rated for a more demanding zone can also be used in less demanding ones of the same gas group and temperature class.
ATEX certifies physical equipment that could become an ignition source in an explosive atmosphere, such as field instruments, motors, and enclosures. A cloud SCADA platform such as Merobix runs on servers and standard computers outside the hazardous area, so the software itself is not ATEX-rated; it reads data from ATEX-certified field devices over protocols like Modbus and DNP3. The certification burden stays with the physical equipment in the classified zone.
Primary references from the standards bodies and regulators that define this topic:
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