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ATEX Equipment, Explosive Atmospheres and Overzoning

Compliance with relevant ATEX directives is a surefire way to protect employees, businesses and the environment from potentially explosive atmospheres.

While it is important to consider the cost factors associated with equipment-based ATEX compliance, businesses may find that proactive and correct zoning can bring about better ROI than a blanket approach.

This holistic approach to explosion safety and zone identification seeks to satisfy the regulators, improve business ROI and ensure that people, the workplace and the environment are kept safe from the inherent risks of fire and explosion.

What is ATEX?

The European Directive known as ATEX aims to ensure that all EU member states enact suitable legislation to improve safety standards and protect workers from explosions brought on by industrial processing activities.

An employer must take organisational and/or technical measures to:

  • prevent the formation of explosive atmospheres, or where the nature of the activity does not allow that, it should avoid the ignition of explosive atmospheres.

  • mitigate the detrimental effects of an explosion to ensure the health and safety of workers.

  • where necessary, measures shall be combined and/or supplemented with measures to prevent the propagation of explosions.

Employers must also assess the specific risks from explosive atmospheres, taking explosion risks into account:

  • the likelihood that explosive atmospheres will occur and their persistence.

  • the likelihood that ignition sources, including electrostatic discharges, will be present and become active and effective.

  • the installations, substances used, processes and their possible interactions.

  • the scale of anticipated effects.

What is a potentially explosive atmosphere?

An explosive atmosphere exists in any situation where a flammable gas, vapour, mist or dust may be present, and the concentration of that particular material in the air is sufficient to allow ignition by a source of flame, spark, or heat.

The ATEX directives define an explosive atmosphere as:

“Mixture with air, under atmospheric conditions, of flammable substances in the form of gases, vapours, mists or dust in which, after an ignition has occurred, combustion spreads to the entire unburned mixture.” (ATEX 114 – article 1.3 & ATEX 153 – article 2)

And a potentially explosive atmosphere as:

“An atmosphere that could become explosive due to local or operational conditions.” (ATEX 114 – article 1.3)

What is a hazardous zone?

Hazardous areas can be divided into three zones: Zone 0/20, Zone 1/21 and Zone 2/22.

Each zone corresponds to a risk level and the potential consequences if an explosion were to occur atex zones.

The most dangerous classification – Zone 0/20 – is classified as such because it’s highly explosive and continuous.

A less dangerous classification is Zone 1/21: it’s still considered potentially hazardous because a flammable atmosphere can accumulate during normal operation conditions e.g., start-up and shutdown operations.

Zone 2/22 is less restrictive in so far as what types of activities can take place without endangering anyone nearby.

Zone 2 refers to the frequency and duration of a flammable atmosphere being unlikely and occurring for only short periods of time e.g., a malfunction, leak, or rip.

What is ATEX rated equipment?

ATEX equipment is designed to meet the requirements of the European Union’s ATEX Directive 94/9/EC, which regulates equipment for use in potentially explosive atmospheres.

This directive applies to any electronic or electrical equipment that could be exposed to an explosive atmosphere, including:

  • process heating equipment (e.g., gas burners and furnaces)

  • pressure vessels

  • explosion-proof electrical equipment (e.g., lighting)

It also considers such items as safety devices, controlling devices and regulating devices which are located outside explosive atmospheres.

Equipment, under ATEX 114 Article 1.3 is described as:

“Machines, apparatus, fixed or mobile devices, control components and instrumentation thereof and detection or prevention systems which, separately or jointly, are intended for the generation, transfer, storage, measurement, control and conversion of energy and/or the processing of material and which are capable of causing an explosion through their own potential sources of ignition.”

Equipment Categories

ATEX 114 equipment consists of two categories:

Group I – for underground mining applications and surface parts of mines liable to be endangered by combustible dust.

  • Categories have been defined (M1 and M2)

Group II (surface industry) there are three categories

  • Category 1 (very high level of protection)

  • Category 2 (high level of protection)

  • Category 3 (normal level of protection)

ATEX Equipment and Blanket Zoning

Although ATEX equipment is more expensive than regular equipment, which can be a major issue for small businesses, it is paramount that the correct equipment is purchased for that particular zone.

The correct application of Hazardous Area Classification (HAC) results in an appropriate budgetary spend on health and safety protection in the workplace.

Furthermore, minimising the use of expensive ‘Ex’ rated equipment and protective systems, if it is required, helps to reduce the level of equipment from potential Category 2 to Category 3.

Maintaining ATEX equipment

It is crucial to maintain ATEX-rated equipment, and if you are required to meet the requirements of ATEX Directive 2014/34/EU, it is important to know how the directive will affect maintenance work.

The applicable standard to be used as a reference for the maintenance of ATEX equipment is:

  • BS EN 60079-17 Electrical apparatus for explosive gas atmospheres – Part 17: Inspection and maintenance of electrical installations in hazardous areas (other than mines)

Other relevant parts of the BS EN 60079 standard that may be required for maintenance of ATEX equipment include BS EN 60079-14 and BS EN 60079-19

EN 60079-17 describes three types and three grades of inspection. The types are:

  • Initial: Utilizing detailed inspection.

  • Periodic: Utilizing visual or close.

  • Sample: Utilizing visual, close and detailed on a proportional basis of the plant.

All equipment should be inspected to verify the safe operating state and must highlight all repair and maintenance requirements based on usage, environmental conditions, breakdown history, historical data/records and manufacturer recommendations.

ATEX Equipment Inspection

Inspection and testing procedures should follow recognized and generally accepted good engineering practices (“RAGAGEP”), which include appropriate internal standards alongside codes and standards published by external bodies e.g., IEC, NFPA, ASTM, EU.

The frequency of inspections and tests should be consistent with applicable manufacturers’ recommendations and, as argued above, recognised and generally accepted good engineering practices.

However occur in normal operation, this should be completed more frequently if determined to be necessary by prior operating experience.


If you process hazardous materials, then you know the importance of complying with ATEX regulations.

While most companies understand the need to comply with these regulations, they may not understand how to do so effectively via correct hazardous zone classifications.

You can’t just assume that everything is okay because it’s been operating without incident for years—you need hard data from experts who will provide recommendations based on their findings.

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