What ATEX means
ATEX stands for ATmosphères EXplosibles, the French term for explosive atmospheres. In practice, ATEX refers to two European Directives that govern equipment and workplaces where explosive atmospheres may form:
- ATEX Directive 2014/34/EU, applies to equipment and protective systems. Manufacturers must certify their products before they can be placed on the European market (and, post-Brexit, the UK market under UKCA).
- ATEX Directive 1999/92/EC, applies to the workplace. Employers must classify hazardous areas into zones and ensure that only appropriately certified equipment is installed in each zone.
An ATEX enclosure is a housing for electrical equipment, terminals, instruments, controls, distribution boards, that has been independently tested and certified to one of the ATEX protection concepts defined in IEC 60079 (the international standard series for explosive atmosphere equipment).
The enclosure itself does not prevent the surrounding atmosphere from being explosive. It prevents any ignition source inside the enclosure from reaching the outside atmosphere, or prevents any ignition source from forming inside at all.
Who needs ATEX enclosures?
ATEX enclosures are required anywhere that a flammable or explosive atmosphere may be present during normal operation, or under foreseeable abnormal conditions. Industries where they are routinely specified include:
- Oil and gas, offshore platforms, refineries, gas compression stations, tank farms
- Chemical processing, plants handling flammable solvents, gases, or dusts
- Pharmaceutical, facilities using flammable solvents in manufacturing and cleaning
- Food and grain processing, dust zones (flour, sugar, grain dust) around mills, dryers, and conveyors
- Paint and coatings, spray booths and mixing areas with flammable solvents
- Wastewater and sewage, sewer gas (methane and hydrogen sulphide) in confined spaces
- Mining, methane and coal dust in underground workings
In the UK, the relevant legislation is DSEAR (Dangerous Substances and Explosive Atmospheres Regulations 2002), which implements the two ATEX Directives into UK law. Post-Brexit, UKCA marking applies for UK market placement.
Reading the ATEX marking
Every certified ATEX enclosure carries a nameplate with standardised marking. A typical example:
⟨Ex⟩ II 2 G D
Ex eb IIC T6 Gb
Ex tb IIIC T80°C Db
IP66
Certificate: EPS 09ATEX1234
| Marking element | Meaning |
|---|---|
| ⟨Ex⟩ | CE-marked explosion protection symbol (hexagonal); ⟨UK Ex⟩ for UKCA |
| II | Equipment Group II, surface industries (Group I = mines) |
| 2 | Category, defines the level of protection and zone suitability (1 = Zone 0/20; 2 = Zone 1/21; 3 = Zone 2/22) |
| G | Gas atmosphere; D = Dust atmosphere; G D = both |
| Ex eb | Protection concept: increased safety, EPL b |
| IIC | Gas group, most stringent (IIC = hydrogen/acetylene; IIB = ethylene; IIA = propane) |
| T6 | Temperature class, maximum surface temperature 85 °C |
| Gb | Equipment Protection Level, Gas, level b (Zone 1/2) |
| Ex tb IIIC T80°C Db | Dust protection: enclosure method, dust group IIIC (conductive), max surface 80 °C, EPL Db |
| IP66 | Ingress protection, dust-tight and powerful jet resistant |
| Certificate number | Issued by the notified body; look up to verify on EU ATEX database |
Materials: GRP, stainless, aluminium
ATEX enclosures are manufactured in several materials, each suited to different environments:
| Material | Advantages | Typical applications |
|---|---|---|
| GRP (Glass Reinforced Polyester) | Lightweight, corrosion-resistant, non-sparking, low cost | Chemical plant, offshore, food processing, coastal |
| 316L Stainless Steel | Hygienically cleanable, marine-grade corrosion resistance, robust | Food, pharma, offshore topsides, coastal marine |
| 304 Stainless Steel | Good corrosion resistance, lower cost than 316L | General industrial, sheltered locations |
| LM6 Aluminium Alloy | Lightweight, good heat dissipation, non-sparking | Zone 1/2 control stations, instrument housings |
| Die Cast GRP / DMC | Complex shapes, small enclosures, antistatic grade available | Zone 0 applications (Ex ia), instrument housings |
GRP enclosures have an important ATEX-specific requirement: the material must not accumulate a dangerous electrostatic charge. Standard polyester GRP can build up charge; ATEX-certified GRP enclosures use either an antistatic resin or a conductive filler to keep surface resistivity below 10⁹ Ω. Enclosures that do not meet this requirement cannot be marked for IIC gas groups or Zone 0.
Cable entries and glands
Cable entries are a critical part of the ATEX system. An enclosure with an improperly fitted gland is not compliant, regardless of how well the enclosure itself is certified.
For Ex eb enclosures, cable glands must:
- Be certified to Ex eb (or Ex e) to the same or higher standard as the enclosure
- Provide the same IP rating as the enclosure when correctly installed
- Grip the cable armour or sheath to provide mechanical retention (pull-out force must meet the standard)
- For SWA (Steel Wire Armoured) cable, provide earth continuity through the armour to the enclosure
Unused entries must be closed with certified blanking plugs, not improvised covers. The blanking plug must maintain the IP rating and be certified to the same protection concept as the enclosure.
Documents you should receive
When you purchase a certified ATEX enclosure, you should receive:
- EC/UK Declaration of Conformity, the manufacturer's declaration that the product meets the Directive requirements
- Certificate of conformity (or a copy), the document issued by the notified body (e.g., Baseefa, Sira, Bureau Veritas)
- Installation and operating instructions, IEC 60079-0 requires these for all certified equipment; they specify conditions of use, temperature ratings, and installation requirements
- Specific Conditions of Use, if the certificate number ends in 'X', there are conditions that must be read and complied with
Keep these documents. Under DSEAR, the duty holder must be able to demonstrate that installed equipment is appropriately certified for the zone in which it is installed. Certificate documents are the evidence.
Maintenance obligations
ATEX equipment does not stay certified indefinitely without maintenance. The key maintenance requirements under IEC 60079-17 are:
- Initial inspection, before energisation; verify all entries, glands, and internal connections comply with the certificate
- Periodic inspection, at intervals determined by the zone and environment; visual, close, and detailed levels defined in the standard
- Gasket condition, silicone and EPDM gaskets degrade in UV exposure and with chemical contact; a failed gasket means the IP rating and Ex protection are compromised
- Fastener torques, lid fasteners on Ex eb enclosures must be re-torqued if disturbed; loose lids compromise IP and protection concept
- Documentation, inspection records must be kept; for Zone 0 and Zone 1, records are required by the standard