What is IEC 60079?
IEC 60079 is the international series of standards for electrical equipment and installations in explosive atmospheres, covering types of protection, marking, installation, inspection and repair wherever flammable gases, vapours or dust may be present. In the Netherlands and the rest of Europe the series applies as NEN-EN-IEC 60079: the European adoption (EN IEC 60079) that NEN, the Dutch standards body, publishes unchanged as the Dutch edition. The series runs to dozens of parts, from the general requirements in Part 0 to the inspection requirements in Part 17. For OT engineers, IEC 60079 determines which sensors, PLCs, drives and even tablets you may use in an Ex zone and how you connect them.
🧠 What does the IEC 60079 series cover?
The series follows the life cycle of a hazardous-area installation. The same set of standards is used by the manufacturer designing a device, the engineer designing the plant and the inspector checking it years later.
- Area classification - Parts 10-1 (gas) and 10-2 (dust) describe how you divide a plant into zones based on how often and for how long an explosive atmosphere occurs
- Equipment - Part 0 holds the general requirements; each further part describes one type of protection, such as flameproof enclosures or intrinsic safety
- Design and installation - Part 14 governs equipment selection per zone, cabling, earthing and documentation
- Inspection and maintenance - Part 17 describes initial and periodic inspections and the inspection grades
- Repair - Part 19 covers repair, overhaul and modification of Ex equipment
- Other parts - including gas detection (Part 29), optical radiation (Part 28) and the properties of gases and vapours (Part 20-1)
🛡️ Which types of protection does IEC 60079 define?
Each type of protection prevents ignition in a different way. The level after the letter (a, b or c) tells you in which zone the equipment may be used.
| Code | Type of protection | Principle | Part | Levels |
|---|---|---|---|---|
| Ex d | Flameproof enclosure | The enclosure withstands an internal explosion and stops flame from escaping | IEC 60079-1 | da, db, dc |
| Ex p | Pressurised enclosure | Clean air or inert gas at overpressure keeps the atmosphere out | IEC 60079-2 | pxb, pyb, pzc |
| Ex e | Increased safety | Additional construction measures prevent sparks and hot surfaces | IEC 60079-7 | eb, ec |
| Ex i | Intrinsic safety | Circuit energy is too low to cause ignition | IEC 60079-11 | ia, ib, ic |
| Ex n | Type of protection n | Sealed devices and restricted-breathing enclosures for zone 2 | IEC 60079-15 | nC, nR |
| Ex m | Encapsulation | The ignition source is potted in compound | IEC 60079-18 | ma, mb, mc |
| Ex o / Ex q | Liquid immersion / powder filling | The ignition source sits under liquid or powder | IEC 60079-6 / -5 | ob, oc / q |
| Ex t | Dust protection by enclosure | Dust-tight enclosure with limited surface temperature | IEC 60079-31 | ta, tb, tc |
With the 2015 edition of IEC 60079-7, the old sub-type Ex nA was absorbed into Ex ec. Since its 2017 edition, Part 15 only covers nC and nR. You will still find Ex nA on older installations, but no longer on new certificates.
🔥 How do zones, EPLs and equipment groups fit together?
The EPL (Equipment Protection Level) is the IEC way of stating how reliably a device prevents ignition. In the EU it maps directly onto the ATEX category.
| Gas zone | Dust zone | Presence of explosive atmosphere | Minimum EPL | ATEX category |
|---|---|---|---|---|
| 0 | 20 | Continuously or for long periods | Ga / Da | 1G / 1D |
| 1 | 21 | Likely during normal operation | Gb / Db | 2G / 2D |
| 2 | 22 | Not likely, and then only briefly | Gc / Dc | 3G / 3D |
IEC 60079-0 also divides equipment into groups. Group I is for mines susceptible to firedamp. Group II is for gas and has three subgroups: IIA (for example propane), IIB (ethylene) and IIC (hydrogen and acetylene), in increasing order of ignitability. Group III is for dust: IIIA (combustible flyings), IIIB (non-conductive dust) and IIIC (conductive dust). Equipment rated for a higher subgroup may be used in a lower one: a IIC device is also suitable for IIA.
The temperature class gives the maximum surface temperature. It must stay below the auto-ignition temperature of the gas present.
| Temperature class | T1 | T2 | T3 | T4 | T5 | T6 |
|---|---|---|---|---|---|---|
| Max. surface temperature | 450 °C | 300 °C | 200 °C | 135 °C | 100 °C | 85 °C |
✅ How do you read an Ex marking?
A device for the European market carries two markings side by side: the ATEX part from Directive 2014/34/EU and the technical part from IEC 60079-0. A typical example for a flameproof junction box:
⬡Ex II 2G Ex db eb IIC T4 Gb
| Element | Origin | Meaning |
|---|---|---|
| ⬡Ex | ATEX | European symbol for explosion-protected equipment |
| II | ATEX | Equipment group II: surface industry, not mining |
| 2G | ATEX | Category 2 for gas: suitable from zone 1 |
| Ex db eb | IEC 60079 | Flameproof enclosure with an increased-safety terminal compartment |
| IIC | IEC 60079 | Gas group IIC: also suitable for hydrogen |
| T4 | IEC 60079 | Surface stays below 135 °C |
| Gb | IEC 60079 | Equipment Protection Level matching zone 1 |
The rating plate also shows the certificate number and, from the 2026 edition of IEC 60079-0 onwards, always the ambient temperature range. A certificate number ending in X means specific conditions of use that you must look up in the certificate.
🔁 What is the difference between IEC 60079 and NEN-EN-IEC 60079?
Technically there is none: NEN-EN-IEC 60079 is the same text as IEC 60079 with a European and Dutch cover page. CENELEC adopts the IEC parts as EN IEC 60079 and NEN publishes them as NEN-EN-IEC 60079. Older European editions, from before the current naming convention, are still called EN 60079 without ‘IEC’. The difference lies in the legal status.
| Edition | Publisher | Status |
|---|---|---|
| IEC 60079 | IEC (worldwide) | Basis for the international IECEx certification scheme |
| EN IEC 60079 | CENELEC (Europe) | Equipment parts are harmonised under Directive 2014/34/EU and give a presumption of conformity |
| NEN-EN-IEC 60079 | NEN (Netherlands) | Dutch edition; the installation and inspection parts are used to meet employer obligations |
An example: EN IEC 60079-0:2018 is the European adoption of IEC 60079-0:2017 and has been listed as a harmonised standard in the Official Journal of the EU since July 2019. The eighth edition of IEC 60079-0 was published in June 2026; the European adoption always follows with some delay. When certifying, always check which edition is currently harmonised.
🧱 Which other standards and rules belong with it?
| Standard or rule | Relationship to IEC 60079 |
|---|---|
| ATEX 2014/34/EU | Product directive; manufacturers demonstrate conformity with the harmonised EN IEC 60079 parts |
| ATEX 1999/92/EC | Workplace directive, implemented in the Netherlands in articles 3.5a to 3.5f of the Working Conditions Decree |
| CE Marking | Ex equipment carries CE; for categories 1 and 2 it also bears the number of the notified body that monitors production |
| Machinery Directive 2006/42/EC | Essential requirement 1.5.7 of Annex I refers machinery for explosive atmospheres to ATEX; the Machinery Regulation applies from 20 January 2027 |
| NEN 1010 | General low-voltage installations; IEC 60079-14 supplements it for Ex zones |
| NEN 3140 | Safe operation and periodic inspection of electrical installations |
| IEC 61439 | Switchgear and controlgear assemblies; in an Ex zone the cabinet also needs an Ex type of protection |
| IEC 60204-1 | Electrical equipment of machines; IEC 60079 applies in addition when used in an Ex zone |
For non-electrical equipment such as pumps and gearboxes, EN ISO 80079-36 and -37 apply. An IECEx certificate is common outside Europe but does not replace an ATEX certificate within the EU.
🏭 How do you apply IEC 60079 in OT projects?
The practical work lies in IEC 60079-14 and -17. A typical approach for an OT project in a chemical plant or tank terminal:
- Get the zone drawing - the area classification is part of the employer’s explosion protection document, in the Netherlands often prepared with NPR 7910-1 (gas) and NPR 7910-2 (dust)
- Determine the requirements per location - the zone, gas group and temperature class of the substances present give the minimum EPL, subgroup and T class
- Choose the type of protection - field instruments with 4-20 mA and HART are usually Ex ia or Ex ib via barriers or isolators; cabinets with a PLC or O are often placed outside the zone, or in an Ex p or Ex d enclosure; motors in Ex db or Ex eb
- Mind digital communication - fieldbuses use FISCO, Ethernet-APL uses 2-WISE from IEC TS 60079-47; wireless devices such as WirelessHART or Wi-Fi need an Ex certificate, and IEC 60079-0 limits radiated RF power (2 W for gas group IIC)
- Document the installation - certificates, Ex i loop calculations, cable schedules and cable glands belong in the verification dossier required by IEC 60079-14
- Inspect periodically - in line with IEC 60079-17, with an initial inspection before commissioning and then periodic inspections, at intervals of no more than three years unless an expert justifies otherwise
A common trap is a variable frequency drive feeding an Ex motor. An Ex eb motor is often certified for mains supply only; converter supply requires a certificate that explicitly permits that combination, because otherwise the motor may run hotter than its T class allows.
⚠️ Which mistakes do you often see in practice?
- Wrong cable glands - an ordinary gland on an Ex d enclosure cancels the flameproof protection
- Mixed Ex i circuits - intrinsically safe and ordinary circuits in the same tray or terminal strip without segregation; Ex i circuits are often marked light blue
- Temperature class or gas group too low - a IIB device is not permitted in a hydrogen atmosphere
- Modifications without reassessment - an extra hole in an enclosure or a different fuse invalidates the certificate
- Insufficient competence - IEC 60079-14 and -17 require demonstrable competence from designers, installers and inspectors; the international IECEx scheme offers a personnel certificate for this
- Forgetting Ex risks of IT equipment - an ordinary laptop, smartphone or edge device is an ignition source and does not belong in a zone without a work permit and gas test
❓ Frequently asked questions
Is NEN-EN-IEC 60079 the same as IEC 60079?
Yes, in content it is. NEN-EN-IEC 60079 is the Dutch edition of the European adoption EN IEC 60079, which in turn takes over the international IEC 60079 text unchanged. The difference is legal: the European equipment parts are harmonised under ATEX Directive 2014/34/EU.
Is IEC 60079 legally mandatory?
IEC 60079 as a standard is not mandatory in itself, but the ATEX directives are. If you comply with the harmonised EN IEC 60079 parts, you gain a presumption of conformity with the product directive. For installation and inspection, NEN-EN-IEC 60079-14 and -17 are the accepted way to meet the Dutch Working Conditions Decree obligations.
Which part of IEC 60079 covers installation?
IEC 60079-14 covers the design, selection and erection of electrical installations in hazardous areas. It describes, among other things, which type of protection is allowed per zone, how to enter cables and how to calculate an Ex i loop. The sixth edition was published in 2024.
How often must an Ex installation be inspected under IEC 60079-17?
IEC 60079-17 requires an initial inspection before commissioning and periodic inspections after that. Without justified expert advice, the interval is no more than three years. The standard defines three inspection grades: visual, close and detailed.
What does T4 mean in an IEC 60079 marking?
T4 means that the surface temperature of the device does not exceed 135 °C under all assessed conditions. The temperature class must be below the auto-ignition temperature of the gas present. T6, at 85 °C, is the strictest class.
What is the difference between IECEx and ATEX?
IECEx is a voluntary international certification scheme based directly on the IEC 60079 standards. ATEX is European legislation that is mandatory for the EU market and refers to the European EN IEC 60079 parts. An IECEx certificate does not replace an ATEX certificate within the EU, but its test reports can support an ATEX assessment.
📌 In summary
IEC 60079 is the technical backbone of explosion protection: the series determines how a device prevents ignition, how you recognise that on the rating plate and how you carry out installation and inspection. In the Netherlands the same content applies as NEN-EN-IEC 60079, linked to ATEX and the Working Conditions Decree. For OT projects this means that every sensor, cabinet, motor and wireless device in an Ex zone needs a suitable EPL, gas group and temperature class.
IEC 60079 and its Dutch adoption NEN-EN-IEC 60079 together form the standard you use to safely select, install and inspect electrical equipment in hazardous areas.