What Is ATEX? A Guide to Explosive Atmospheres and Ex Equipment Selection

In many sectors – chemicals, paint, textiles, flour and grain, pharmaceuticals, petrochemicals and energy – explosive atmospheres can form from flammable gases, vapours, mists or dusts. Choosing the wrong Ex equipment for these environments – often referred to in the field as “exproof” – creates a serious risk to both personnel and plant safety. In this article we explain, step by step, what an explosive atmosphere is, how hazardous areas are classified, how equipment is selected and certified under ATEX (2014/34/EU), and the employer’s legal obligations.

01How Does an Explosive Atmosphere Form?

For an explosion to occur, three elements must come together at the same time; this relationship is explained by the “fire triangle”: a sufficient quantity of fuel (gas, vapour, mist or dust), oxygen (air) in the environment, and an ignition source. An explosion occurs when the fuel mixes with air within a certain concentration range (the lower/upper explosion limits – LEL/UEL) and meets an ignition source with enough energy.

THREE ELEMENTS TOGETHER

AT THE RIGHT MIXTURE RATIO

IGNITION SOURCESSparks from electrical equipment · hot surfaces · static electricity · mechanical friction · electromagnetic waves

Ignition sources are not only open flames. A spark in electrical equipment, hot surfaces, static electricity, mechanical friction sparks, electromagnetic waves and even an unsuitable flashlight can all cause ignition. For this reason, every piece of equipment used in explosive atmospheres must be designed to keep potential ignition sources under control.

The most common ignition scenarios in the field

The situations below are habits that seem harmless on their own but can end in an explosion in an environment where fuel is present.

02Classification of Hazardous Areas (Zones)

Work areas are classified as hazardous areas according to the likelihood and duration of an explosive atmosphere occurring. Zone 0-1-2 is used for gases, vapours and mists, and Zone 20-21-22 for combustible dusts. The more hazardous the area, the higher the level of protection required from the equipment used there.

Area classification is carried out according to EN 60079-10-1 (gas) and EN 60079-10-2 (dust).

Zone 0 – inside tanks and vesselsZone 1 – around filling and discharge pointsZone 2 – surrounding plant area

03Equipment Groups, Categories and EPL

2014/34/EU divides equipment into two groups: Group I is used for underground mines and facilities where firedamp is a hazard; Group II is used for all other surface industries. The letter G next to the category number indicates a gas environment and D a dust environment. The Equipment Protection Level (EPL) determines which zone the equipment may enter.

04How to Read Ex Marking

A product to be used in an explosive atmosphere carries a standard Ex marking showing the conditions it is suitable for. Let us break down an example marking piece by piece:

Module B alone is not sufficient to place a product on the market. Depending on the product category, one of the routes B+D, B+F, B+C1 or B+E is completed, or Module G unit verification is applied. Once the relevant process is completed and the EU Declaration of Conformity is issued, the CE mark is affixed. Next to the CE mark is the identification number of the notified body involved under module D, E, F, C1 or G. Under Module A, the CE mark is used without a notified body number.

05Types of Protection

The type of protection shows the principle by which the equipment prevents ignition. The lower-case letters (a/b/c) indicate the protection level: “a” is the highest and “c” the lowest.

06Gas/Dust Groups and Temperature Classes

The suitability of equipment is determined not only by the zone but also by the ignition properties of the substance present. The two key parameters are the gas/dust group and the temperature class.

The maximum surface temperature of the equipment must be lower than the ignition temperature of the substance present. For example, for a substance with an ignition temperature of 150 °C, at most class T4 (≤135 °C) can be selected.

The colour indicates temperature, not danger: T6 is the class that stays coolest and therefore has the widest range of use.

For dusts, the temperature is stated directly as the maximum surface temperature (e.g. T135 °C) rather than as a class.

07ATEXvsIECExCoCKey Differences

These two systems, often confused in practice, complement each other but differ in legal nature. Both are largely based on the same IEC 60079 family of standards. ATEX is mandatory for placing products on the Turkish and EU market; an IECEx certificate provides additional ease of acceptance for export, but does not replace the ATEX obligation.

08Scope of ATEX (2014/34/EU) and CE + Ex Marking

ATEX takes its name from the expression “ATmosphères EXplosibles”. In Turkey, the product rules are set out in the Regulation on Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres (2014/34/EU). For a product to bear the CE mark, the ATEX obligations must also be fulfilled, and the appropriate Ex marking – and, where required, the notified body number – must appear alongside the CE mark. The manufacturer’s essential obligations are:

• Design and manufacture in accordance with the essential health and safety requirements (Annex II),
• Preparation and retention of the technical file,
• Application of the conformity assessment procedure appropriate to the product category,
• Drawing up the EU Declaration of Conformity and affixing the CE + Ex marking,
• Provision of instructions for use and traceability information.

09Conformity Assessment Modules

The procedure to be applied varies according to the equipment’s category and type (electrical/non-electrical). As the risk increases, so does the involvement of the notified body.

Note: Although manufacturer self-declaration is possible for Category 3 gas equipment, there are type-specific rules – such as depositing the technical file with a notified body for non-electrical Category 2 equipment. The module to be applied is determined by the product’s category and type.

11Inspection and Maintenance (Continued Compliance)

Selecting the right equipment is not enough on its own; you must make sure that Ex installations maintain their protection throughout their service life. Under EN 60079-17, periodic inspections are defined at three levels – visual, close and detailed. An initial inspection is carried out at commissioning; periodic inspection then continues at intervals determined by the level of risk.

12The Employer’s Obligation: Explosion Protection Document

ATEX has not only a product side but also a workplace side. In Turkey, under the Regulation on the Protection of Workers from the Risks of Explosive Atmospheres (based on 1999/92/EC), the employer is obliged to assess explosion risks, classify hazardous areas (zones), select equipment of the appropriate category for those areas, and prepare and keep up to date the Explosion Protection Document (EPD).

13Selecting the Right Ex Equipment: Step by Step

14Common Mistakes

15Frequently Asked Questions