ATEX

What is ATEX?

ATEX is the collective name for two European directives that control explosion hazards: Directive 2014/34/EU sets requirements for equipment and protective systems intended for explosive atmospheres, and Directive 1999/92/EC obliges employers to protect workers in places where flammable gases, vapours, mists or dust can form an explosive atmosphere. The name comes from the French ATmosphères EXplosibles. ATEX affects every chemical plant, refinery, tank terminal, flour mill, wastewater plant with biogas and hydrogen installation in the EU. It is a cornerstone of process safety, and for OT engineers it decides which PLCs, sensors, cables and even tablets you may use in an Ex-zone.

🧠 What are the two ATEX directives?

ATEX consists of a product directive for manufacturers and a user directive for employers. Both use the same zone classification and the same equipment categories, so the chain from design to use fits together.

The nicknames refer to the article of the EU Treaty on which each directive is based: Article 114 (internal market) and Article 153 (social policy, Article 137 before the treaty was renumbered). Certificates issued under the old Directive 94/9/EC remain valid under 2014/34/EU.

🧯 When does an explosive atmosphere arise?

An explosion requires three things at the same time, known as the explosion triangle:

1. Flammable substance: gas, vapour, mist or dust at a concentration between the lower and upper explosive limit (for methane roughly 4.4 to 17 per cent by volume in air)
2. Oxygen: normally just the surrounding air
3. Ignition source: with sufficient energy or temperature

The standard EN 1127-1 distinguishes thirteen types of ignition source, including hot surfaces, flames, mechanically generated sparks, electrical equipment, stray currents, static electricity, lightning, radio-frequency waves, ultrasound, adiabatic compression and exothermic reactions. That list matters for OT: it is not only a relay or terminal block that can ignite a mixture, but also a radio transmitter or a statically charged plastic enclosure.

The ATEX approach follows a fixed order of priority. First, you prevent an explosive atmosphere from forming (closed systems, ventilation, inerting with nitrogen). Where that cannot be done completely, you avoid ignition sources. Finally, you limit the consequences with measures such as explosion vents or pressure-resistant construction.

🧭 How are ATEX zones classified?

The employer divides the plant into hazardous zones based on how often and for how long an explosive atmosphere is present. The zone determines the minimum equipment category required.

Area classification is carried out according to IEC 60079-10-1 (gas) and IEC 60079-10-2 (dust); in the Netherlands the practical guidelines NPR 7910-1 (gases and liquids) and NPR 7910-2 (dust) are widely used. A common mistake is to over-classify “to be on the safe side”: a larger zone 1 means more expensive equipment, more inspection work and more work permits, without any real gain in safety.

⚙️ How do you read an ATEX marking?

ATEX equipment carries a marking in two parts: the European part from the directive and the technical part from the IEC 60079 series. A typical example:

CE 0344 ⬡Ex II 2G Ex db IIC T4 Gb

The gas group and temperature class must suit the substances in your plant. Equipment rated for a more demanding group may always be used in a less demanding one, never the other way round.

The gas group is independent of the temperature class. IIA has propane as its reference gas (acetone and methane also fall under it), IIB has ethylene, and IIC covers hydrogen and acetylene, which have the lowest ignition energy at around 0.02 mJ. For dust there are groups IIIA (combustible flyings), IIIB (non-conductive dust) and IIIC (conductive dust), and the maximum surface temperature is stated directly in degrees on the label, for example T135 °C.

🔧 How does a manufacturer demonstrate conformity?

The product directive links the depth of assessment to the category. The higher the level of protection, the more a notified body has to do:

• Category 1 and M1: EU-type examination by a notified body, plus production quality assurance or product verification
• Category 2 and M2, electrical equipment and internal combustion engines: EU-type examination plus internal production control with supervised product testing, or product quality assurance
• Category 2, non-electrical equipment: internal production control, with the technical file lodged with a notified body
• Category 3: internal production control by the manufacturer alone

Electrical equipment is assessed against the harmonised NEN-EN-IEC 60079 standards; non-electrical equipment such as pumps, couplings and gearboxes falls under EN ISO 80079-36 and -37. The international IECEx certificate is common outside Europe, but within the EU it does not replace an ATEX certificate. IECEx test reports can, however, support an ATEX application.

🏭 What does ATEX mean for OT and IT/OT convergence?

Digitalisation brings more and more electronics and radio into process plants, and with them more potential ignition sources. Typical design choices:

IT decisions have an ATEX side too. Rolling out a wireless network across a chemical site, replacing an industrial switch with a different model or introducing a mobile inspection app are all changes that can affect the explosion protection document. Conversely, remote maintenance reduces the number of times someone has to enter an Ex zone with tools.

🛠️ How do you tackle ATEX in a Dutch plant?

In the Netherlands the user directive is implemented in the Arbobesluit under the Arbowet, and the Netherlands Labour Authority (Nederlandse Arbeidsinspectie) supervises compliance. A workable approach in seven steps:

1. Inventory flammable substances, their properties (flash point, explosive limits, gas group, ignition temperature) and release sources as part of the RI&E risk assessment
2. Classify zones according to NPR 7910-1/-2 and record them on drawings; use a HAZOP to include abnormal process conditions
3. Draw up the explosion protection document (explosieveiligheidsdocument, EVD) before work starts, and update it after every significant change, extension or conversion (article 3.5c Arbobesluit)
4. Select equipment per zone according to article 3.5e, with a suitable gas group and temperature class
5. Install according to NEN-EN-IEC 60079-14 and, for the rest of the low-voltage installation, NEN 1010; before first commissioning and after every significant change, have a competent person verify the explosion safety of the entire installation (article 3.5e, item i)
6. Inspect and maintain according to NEN-EN-IEC 60079-17; without expert advice the periodic inspection interval should not exceed three years
7. Organise the work with work permits, gas measurements, non-sparking tools, earthing and authorised staff according to NEN 3140

In 2020 article 3.5e was clarified (Staatsblad 2020, 26): the wording that the explosion protection document could set “other requirements” became “additional requirements”. According to the explanatory memorandum, the document therefore may not permit a less stringent zone or equipment category; only where suitable equipment is not available may you deviate, with extra measures. In practice this mainly affected mobile equipment. Because no Ex version exists for some measuring instruments and battery tools, the Labour Authority published an adjusted supervisory approach on 2 March 2023. It allows non-certified equipment by exception, but only in zone 2 or 22 and only after an ATEX expert has assessed all ignition sources. The industry associations VNCI, Vemobin, VOTOB, NOVE and Deltalinqs worked this out in an industry guide (version 4.0, August 2024), with a step-by-step plan that starts with certified equipment and only allows a tailored solution as the last step.

If your site also falls under the Seveso rules, ATEX, functional safety and cybersecurity are directly linked: a safety function that shuts down a plant on gas detection is only reliable if the control system behind it is protected as well.

⚠️ What risks do you run without an ATEX approach?

• Explosion and fire: with a risk of fatal injury and destruction of plant; dust explosions in silos can propagate through a building via secondary explosions
• Enforcement: the Labour Authority can impose a fine or stop the work if the explosion protection document is missing or the equipment does not match the zone
• Liability: after an incident, a court will assess whether you followed the state of the art
• Hidden technical debt: a replacement sensor or switch without the correct marking silently makes a previously compliant installation unsafe

❓ Frequently asked questions

Is ATEX mandatory in the Netherlands?

Yes, ATEX is a legal requirement in the Netherlands. The product directive 2014/34/EU is transposed in the Warenwetbesluit explosieveilig materieel 2016 and the user directive 1999/92/EC in articles 3.5a to 3.5f of the Arbobesluit. Every employer with a potential explosive atmosphere must therefore classify zones and draw up an explosion protection document.

What is the difference between ATEX and IECEx?

ATEX is European legislation and is mandatory for equipment placed on the EU market. IECEx is a voluntary international certification scheme based on the IEC 60079 standards, which is mainly required outside Europe. An IECEx certificate does not replace an ATEX certificate, but its test reports can support an ATEX assessment.

What does an explosion protection document contain?

An explosion protection document describes the identified explosion risks, the zone classification, the technical and organisational measures taken and how workplaces, equipment and alarm systems are designed, used and maintained safely. Where several employers work at the same location, it also records how their work is coordinated. The document must be ready before work starts and must be updated after every significant change to the plant or work process (article 3.5c of the Dutch Arbobesluit).

Can I use an ordinary smartphone in an ATEX zone?

An ordinary smartphone is an ignition source because of its battery, electronics and radio transmitter, so in principle it is not allowed in an ATEX zone. Use an Ex-certified device of the correct category, or work only after a gas-free certificate has been issued under a work permit. Since March 2023 the Dutch Labour Authority accepts exceptions only in zones 2 and 22, and only after an assessment by an ATEX expert.

Which ATEX category belongs to which zone?

Zones 0 and 20 require category 1 equipment, zones 1 and 21 category 1 or 2, and zones 2 and 22 category 1, 2 or 3. In addition, the gas or dust group and the temperature class of the device must suit the substances present. A higher category may therefore always be used in a less hazardous zone, but not the other way round.

How often must ATEX equipment be inspected?

ATEX installations are inspected according to NEN-EN-IEC 60079-17, with an initial inspection before commissioning followed by periodic inspections. Without expert advice the periodic interval should not exceed three years. The standard defines three grades of inspection (visual, close and detailed); the grade and sample size you choose follow from the risk and the environmental conditions.

📌 In summary

ATEX consists of two European directives: 2014/34/EU for the manufacturer of equipment and 1999/92/EC for the employer who uses it. Together they define how you identify explosion hazards, classify zones, document everything in an explosion protection document and control the risk with equipment of the right category, gas group and temperature class. For OT this means intrinsically safe instrumentation, careful placement of control cabinets and a critical look at every new wireless or mobile application.

ATEX is the European legal framework that requires manufacturers and employers to eliminate ignition sources in hazardous zones, from equipment design to the daily work permit.