--- title: Ex technical information | ATEX, IECEx, zones, marking description: Plain-language reference on ATEX, UKEX, IECEx, ISO 80079-34, DSEAR, hazardous area zones, Ex marking, gas groups, T classes, IP ratings and Annex C. --- [![insightEx](https://insightex.co.uk/hubfs/website/insightex-logo-dark.jpg)](https://insightex.co.uk/?hsLang=en-gb) [Services▾](https://insightex.co.uk/insightex-one?hsLang=en-gb) [insightEx one](https://insightex.co.uk/insightex-one?hsLang=en-gb)[QAN QAR implementation](https://insightex.co.uk/qan-qar-implementation?hsLang=en-gb)[Consultancy](https://insightex.co.uk/consultancy?hsLang=en-gb)[Routes to certification](https://insightex.co.uk/routes-to-certification?hsLang=en-gb)[Shop](https://insightex.co.uk/shop?hsLang=en-gb) [About us](https://insightex.co.uk/about?hsLang=en-gb) [Resources▾](https://insightex.co.uk/technical-information?hsLang=en-gb) [Technical Info](https://insightex.co.uk/technical-information?hsLang=en-gb)[Downloads](https://insightex.co.uk/downloads?hsLang=en-gb)[Blog](https://insightex.co.uk/blog?hsLang=en-gb) [Contact us](https://insightex.co.uk/contact?hsLang=en-gb)[Book a demo](https://insightex.co.uk/contact#book) Menu Services [insightEx one](https://insightex.co.uk/insightex-one?hsLang=en-gb)[QAN QAR implementation](https://insightex.co.uk/qan-qar-implementation?hsLang=en-gb)[Consultancy](https://insightex.co.uk/consultancy?hsLang=en-gb)[Routes to certification](https://insightex.co.uk/routes-to-certification?hsLang=en-gb)[Shop](https://insightex.co.uk/shop?hsLang=en-gb) Resources [Technical Info](https://insightex.co.uk/technical-information?hsLang=en-gb)[Downloads](https://insightex.co.uk/downloads?hsLang=en-gb)[Blog](https://insightex.co.uk/blog?hsLang=en-gb) Company [About us](https://insightex.co.uk/about?hsLang=en-gb)[Contact us](https://insightex.co.uk/contact?hsLang=en-gb)[Book a demo](https://insightex.co.uk/contact#book) ResourcesTechnical # Technical information. A plain-language reference for Ex and hazardous area compliance: ATEX, UKEX, IECEx, ISO 80079-34, area classification, equipment marking and protection concepts, in one place. Written by our technical experts who work to these standards, for engineers who have to apply them. [Ask us a question](https://insightex.co.uk/contact?hsLang=en-gb)[Downloads](https://insightex.co.uk/downloads?hsLang=en-gb) 01 Standards & regulations [What is ISO 80079-34?](https://insightex.co.uk/technical-information#iso-80079-34)[ATEX vs DSEAR](https://insightex.co.uk/technical-information#atex-vs-dsear)[NRTL vs ATEX and IECEx](https://insightex.co.uk/technical-information#nrtl-vs-atex-iecex)[Mining vs non-mining](https://insightex.co.uk/technical-information#mining-vs-non-mining)[Ex competence requirements](https://insightex.co.uk/technical-information#competence) 02 Certification & audits [What is a QAN QAR audit?](https://insightex.co.uk/technical-information#qan-qar-audit)[What is IECEx certification?](https://insightex.co.uk/technical-information#iecex-certification)[What is a competency matrix?](https://insightex.co.uk/technical-information#competency-matrix) 03 Ex equipment [Ex marking strings explained](https://insightex.co.uk/technical-information#ex-marking)[Hazardous area classification](https://insightex.co.uk/technical-information#area-classification)[Concepts of protection](https://insightex.co.uk/technical-information#protection-concepts)[Gas groups](https://insightex.co.uk/technical-information#gas-groups)[Dust groups](https://insightex.co.uk/technical-information#dust-groups)[Temperature classes](https://insightex.co.uk/technical-information#temperature-classes)[Service vs surface temperature](https://insightex.co.uk/technical-information#service-vs-surface)[Ingress protection](https://insightex.co.uk/technical-information#ingress-protection)[Cable and gland selection](https://insightex.co.uk/technical-information#cable-and-glands) 01 ## Standards & regulations What the law and the standards require, and which of them apply to you as a manufacturer, an employer, or both. ## What is ISO 80079-34? ISO/IEC 80079-34 is the quality system standard for manufacturers of equipment used in explosive atmospheres. It sets out what your quality management system must control so that every unit you ship still conforms to its certificate. It builds on ISO 9001 and adds the Ex-specific requirements: documented competence for every role that affects conformity, control of Ex-critical manufacturing steps, calibration of the instruments that prove conformity, routine inspection and test, and the records that support your Declaration of Conformity. ATEX 2014/34/EU requires a production quality assurance route for Category 1 and 2 equipment, and ISO/IEC 80079-34 is the standard a notified body assesses against when it issues a Quality Assurance Notification. If you hold or need a QAN or a QAR, you are being assessed to this standard. ## ATEX vs DSEAR The ATEX “Equipment Directive” governs equipment placed on the market. DSEAR (in the UK) governs the workplace. They apply at different stages, and neither one discharges the other. ATEX 2014/34/EU, and UKEX for Great Britain, place duties on the manufacturer. You meet them through type examination where required, a quality system, the correct marking and an EU or UK Declaration of Conformity. The Dangerous Substances and Explosive Atmospheres Regulations 2002 place duties on the employer or site operator: classify the hazardous areas, control ignition sources, and select equipment appropriate to the zone. No body issues a DSEAR certificate, because DSEAR is not a certification route. The two meet at zone and category. The site classifies its zones under DSEAR; the equipment carries a category and an equipment protection level from its certificate. Lining those up is what hazardous area classification is for. A manufacturer that also operates a plant with hazardous areas carries both sets of duties, assessed separately. ## NRTL vs ATEX and IECEx North America runs a parallel system. Equipment must be listed or certified by a Nationally Recognized Testing Laboratory, and the classification scheme uses Classes and Divisions alongside the Zone system. ATEX, UKEX and IECEx all test to the IEC 60079 series, so one set of testing usually supports all three submissions. NRTL certification works to its own standards and with a slightly different system, so those are separate pieces of work rather than a paperwork exercise on top (in most cases). The practical consequence is that certification follows the market, not the product. The same piece of equipment can need multiple certificates to be sold worldwide, and deciding the order before you start is what keeps the cost down. ## Mining vs non-mining equipment Equipment Group I covers mines susceptible to firedamp and coal dust. Group II covers all other explosive gas atmospheres, and Group III covers dust atmospheres outside mining. Mining is treated separately because the hazard is different. Firedamp and coal dust are present as a condition of the work rather than as an occasional release, so Group I equipment carries its own equipment protection levels, Ma and Mb, rather than the Ga, Gb and Gc used for surface gas atmospheres. Ma equipment must remain functional and safe even with an explosive atmosphere present, because in a mine you cannot simply isolate and evacuate in the same way. Mb equipment must be de-energised in that situation. Marking, testing and certification all follow from that distinction, and Group II equipment is not interchangeable with Group I. ## Ex competence requirements ISO/IEC 80079-34 requires documented competence across ten roles, from the shop floor to marketing, not just for engineers. Competence has to be evidenced. The particular roles named are Ex Authorised Person, manufacturing, engineering, inspecting, testing, quality control, sales, marketing, purchasing and calibration. Each needs a defined level of Ex knowledge appropriate to what it does, and each needs records an assessor can review: training with assessment, practical demonstration where relevant, and periodic re-assessment. The Ex Authorised Person carries the most: full working knowledge of the applicable standards, the quality system, the conformity assessment procedure, the technical file and the conditions attached to each certificate, held under a written mandate. Where one person holds several of these roles, the competence and evidence requirements are cumulative. 02 ## Certification & audits How certification works in practice, and what happens when an assessor arrives. ## What is a QAN QAR audit? A QAN or QAR audit is an assessment of your quality system against ISO/IEC 80079-34, carried out by a notified body or an IECEx certification body. ATEX and UKEX issue a Quality Assurance Notification; IECEx issues a Quality Assessment Report. The assessor is not checking whether your product design is sound, that is what type examination does. They are checking that your system reliably reproduces the certified design: that Ex-critical processes are controlled, that the people carrying them out are demonstrably competent, that measuring equipment is calibrated, that routine inspection and test happen and are recorded, and that non-conforming product is caught and handled. Initial assessment is on site. Surveillance follows periodically, typically annually for ATEX QAN and at intervals set by the scheme for IECEx QAR. Findings are graded, and major non-conformances must be closed before the notification is issued or maintained. SchemeOutputAssessed byAgainst ATEXQuality Assurance Notification (QAN)Notified bodyISO/IEC 80079‑34 UKEXQuality Assurance Notification (QAN)UK approved bodyISO/IEC 80079‑34 IECExQuality Assessment Report (QAR)IECEx certification bodyISO/IEC 80079‑34 ## What is IECEx certification? IECEx is the international certification scheme for equipment used in explosive atmospheres. A Certificate of Conformity is issued against the IEC 60079 and 80079 series, and is recognised by member countries worldwide. An IECEx Certificate of Conformity rests on two things: a test report demonstrating the design meets the applicable standards, and a Quality Assessment Report demonstrating your manufacturing can reproduce it. Neither on its own is enough. Because ATEX, UKEX and IECEx all test to the same IEC standards, one set of testing normally supports all three submissions. IECEx is often the efficient place to start if you sell into more than one region, as the test evidence carries across. It is a voluntary scheme, unlike ATEX, which is law for the EU market. ## What is a competency matrix? A competency matrix maps every role in your organisation against the Ex knowledge that role requires, and records the evidence that each person holds it. It is the document that turns a competence claim into something auditable. ISO/IEC 80079-34 requires competence to be defined, achieved and maintained, but does not prescribe the format. In practice a matrix is what assessors expect to see: roles down one axis, required knowledge across the other, and for each intersection the training completed, the assessment passed and the date it needs revisiting. The common failure is a matrix that lists attendance rather than competence, and is not kept up to date. 03 ## Ex equipment Marking, classification, protection concepts, temperature and selection. The reference tables, as they appear in the standards. ## Ex marking strings explained An ATEX and IECEx marking string consists of six pieces of information: group, EPL and category, type of protection, gas or dust group, temperature class, and IP rating. Read in that order it stops being a code and becomes a specification. Each element answers a different question, and each is selected in sequence, because the earlier choices constrain the later ones. The zone sets the EPL and category; the EPL determines which types of protection are permitted; the environment sets the gas or dust group and the temperature class. One quirk catches people out. The EPL is decided at step 2 but does not appear at that position in the marking, it sits after the gas group. So the string is not read in the same order it is built. STEP 1 I Group Mine susceptible to firedamp, or above ground STEP 2 2G EPL + category Derived from the zone the equipment is for STEP 3 Ex db Type of protection How the ignition risk is removed STEP 4 IIC Gas and dust group The ignitability of the atmosphere STEP 5 T4 Temperature class Maximum surface temperature STEP 6 IP66 IP rating Ingress of solids and water Worked examples: I M2 Ex db T5 Mb IP66 (mining), II 2G Ex db IIC T4 Gb IP66/67/68 (gas), II 1D Ex ta IIIC T130°C Da IP64 (dust). ## Hazardous area classification Zones describe how often an explosive atmosphere is present. The zone is determined by the site, by a competent person, to IEC 60079-10-1 for gas and 60079-10-2 for dust. Equipment is then selected to match. Zone determines equipment protection level and ATEX category directly. Equipment rated for a more onerous zone may always be used in a less onerous one: equipment certified for Zone 1, EPL Gb, Category 2G, is acceptable in Zone 2. The reverse is never true. Gas zoneDust zoneAtmosphere presentEPLATEX category 020Continuously or for long periodsGa / Da1G / 1D 121Likely in normal operationGb / Db2G / 2D 222Not likely in normal operationGc / Dc3G / 3D MineMineFiredamp or coal dustMa / MbM1 / M2 ## Concepts of protection A type of protection is the engineering method used to remove the ignition risk. Which ones are permitted depends on the EPL, and therefore on the zone. The lower the risk, the more options are open to you. IEC 60079-14 sets out which types are permitted where. The choice is risk-based mitigation, not preference: a Zone 0 application allows very few concepts, a Zone 2 application allows many. CodeProtectionStandard Ex dFlameproofEN IEC 60079-1 Ex eIncreased safetyEN IEC 60079-7 Ex hNon-electricalEN ISO 80079‑36 EN ISO 80079‑37 Ex iIntrinsic safetyEN IEC 60079-11 Ex mEncapsulationEN IEC 60079-18 Ex nReduced riskEN IEC 60079-15 Ex oOil immersionEN IEC 60079-6 Ex opOptical radiationEN IEC 60079-28 Ex pPressurised (purge)EN IEC 60079-2 Ex qPowder (quartz) filledEN IEC 60079-5 Ex sSpecialEN IEC 60079-33 Ex tEnclosure (dust)EN IEC 60079-31 ## Gas groups Gases are grouped by ignitability. IIC gases are the most easily ignited and the hardest to protect against; IIA the least. Equipment certified for IIC is acceptable in IIB and IIA atmospheres. GroupTypical gases IICHydrogen, acetylene IIBEthylene, ethanol IIAAmmonia, butane, propane, methane, petrol, iso-propyl alcohol ## Dust groups Dusts are grouped by type rather than ignitability. Conductive dusts are the most onerous, because they can bridge electrical parts as well as ignite. GroupTypeExamples IIICConductive dustAluminium, bronze, zinc, magnesium IIIBNon-conductive dustSugar, flour, grain, milk powder IIIACombustible flyingsSaw dust, tobacco ## Temperature classes The temperature class caps the maximum surface temperature the equipment may reach, so that it stays below the auto-ignition temperature of the atmosphere it is used in. Select the class against the gas actually present. Carbon disulphide auto-ignites at 95°C, so it demands T6. Hydrogen auto-ignites at 560°C and is satisfied by T1, despite being a IIC gas. Ignitability and ignition temperature are different properties and are selected against separately. T classMax surface tempExample gas and its auto-ignition temp T1450°CHydrogen, 560°C T2300°CButane, 372°C T3200°CKerosene, 210°C T4135°CDi-ethyl ether, 160°C T5100°CNothing common T685°CCarbon disulphide, 95°C ## Service temperature vs surface temperature They are not the same limit, and meeting one does not mean meeting the other. Service temperature is the ambient range the equipment is certified to operate within. Surface temperature is the hottest the equipment itself may become. The temperature class governs surface temperature, and the actual maximum surface temperature will always be below the class limit: a T4 device stays under 135°C. Service temperature is a separate marking, typically shown as an ambient range such as -20°C to +40°C, and operating outside it invalidates the certificate regardless of how cool the surface stays. Dust applications are marked differently again. The maximum surface temperature is given in degrees Celsius, calculated with a defined layer of dust present, rather than as a T class, which is why a dust marking reads T130°C rather than T4. ## Ingress protection An IP rating has two numerals. The first is protection against solids, the second against water. It is a construction rating, not an Ex rating, but it is load-bearing for Ex conformity where the protection concept depends on the enclosure. Ex t dust protection in particular relies on the enclosure keeping dust out, so the IP rating is part of how the protection concept is achieved rather than an incidental extra. First numeralProtection against solids XNo protection against objects 1Effective against a large surface, over 50 mm 2Effective against a finger or similar, over 12.5 mm 3Effective against tools and thick wires, over 2.5 mm 4Effective against most wires, over 1 mm 5Dust protected: not fully prevented, but not enough to interfere with operation 6Dust tight: no ingress of dust after an 8 hour test with vacuum applied Second numeralProtection against water XNo protection against water 1Dripping water 2Dripping water when tilted up to 15° 3Water falling at up to 60° from vertical 4Splashing water from any direction 5Water spray from a 6.3 mm nozzle, any direction 6Powerful jets from a 12.5 mm nozzle 7Submersion up to 1 m 8Submersion under conditions specified by the manufacturer 9High pressure and steam jet cleaning 9KAs 9, but at high temperature ## Cable and gland selection IEC 60079-14:2024 restructured Ex d cable and gland selection around a single flowchart, and made the Annex C cable pressure test normative. Cable and gland can no longer be treated as separate decisions. The flowchart asks about gas group, cable length and enclosure volume, and routes you either to a barrier-type entry device or to an elastomeric-seal device supported by evidence. On the IIA or IIB branch that evidence is needed where the cable meets the 0.5 m minimum but the enclosure volume is 2,000 cm³ or more, or cannot be confirmed. On the IIC or IIB plus hydrogen branch it applies to cables of at least 3 m. The Annex C test itself is short: a 0.5 m sample fitted to a 5,000 cm³ enclosure, pressurised to 0.3 kPa and isolated, must not lose more than 50 per cent of that pressure in 5 seconds. A pass is specific to the tested construction, identified by manufacturer, type, size and conductor count. A catalogue reference on its own may not be sufficient evidence. Free Ex competence scorecard ## Reading up, or filling a gap? 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