What are ATEX Zones and Equipment Categories?

Ex-Machinery explains “which ATEX equipment may be used in which ATEX zone?”


Put this practical overview on your bulletinboard!

Within Europe, electronic or electrical equipment of any kind that is intended for use in a potentially hazardous area must be ATEX-certified, as per the EU directive 2014/34. This directive is more commonly known as the ATEX 114 directive (derived from the French ‘ATmosphères EXplosives’).

ATEX equipment is classified into groups and categories, which are indicated by the markings on the equipment. Hazardous areas are divided into zones based on the likelihood of a potentially explosive atmosphere being present. For many of our clients, the following question arises: how to determine which ATEX equipment can be used in which Ex zone?

As specialists in ATEX and explosion safety, Ex-Machinery offers an easy-to-use reference guide to help answer these questions. Let’s take a look…

[CHART] ATEX Zones, Equipment Categories and Markings

The table above shows the relationship between ATEX Zones, Equipment Categories and the Ex Marking.

Let’s start with a practical example:

An air conditioner for ATEX zone 2 (gas) falls into category 3 for explosion proof equipment. Meanwhile, for ATEX zone 1 (gas), category 2 explosion proof equipment is necessary.

Does that seem confusing to you? It might at first, but we assure you, there is a logical explanation.

Classification of ATEX Zones Based on Risk Level

Ex zones begin at 0 for gases and 20 for dust, while equipment classifications start at 1. The terms ‘ATEX zones’ and ‘ATEX equipment categories’ each have distinct origins and numbering systems, which we will explore further later in this article.

The frequency with which an explosive atmosphere appears during normal operations dictates the classification of ATEX zones for combustible dust and flammable gases:

  • Zone 0 or 20 is for environments where an explosive atmosphere is constantly present, such as inside a tank.
  • Zone 1 or 21 applies if an explosive atmosphere is present only intermittently.
  • For environments where an explosive atmosphere is a rare occurrence during normal operations, such as the area surrounding a Zone 1/21 where flammable substances might occasionally spill over, the classification would be Zone 2 or 22.
Atex zones and presence of the explosive atmosphere, explained.
An excerpt of our ATEX Basics Infographic, detailling ATEX zones, markings and explosive atmosphere frequency.

Explosive Atmospheres and Ex Zones

We now understand that potentially explosive atmospheres can be categorized into two types, based on the type and presence of flammable substances. In general, the terms ATEX Zones, Ex Zones, and Explosive Atmospheres all denote the same concept.

As we have already discussed, zones 0/1/2 are designated for areas with flammable gases. These gases might originate from temporary leaks and spills, or they may be persistently present, as seen in ATEX Zone 0. For areas with combustible dusts, zones 20/21/22 are used.

Understanding The Risks in Ex Zones

It’s important to recognize that merely having flammable substances present does not suffice to cause an explosion. To create an explosion hazard, flammable dust or combustible gases must first mix with an appropriate amount of oxygen to form an explosive mixture. Only when this mixture encounters an ignition source do the risks escalate significantly, potentially leading to catastrophic outcomes.

Ignition sources are not always what you would expect – for example, a mobile device can produce electrical arcs.

illustration of electrical spark

ATEX Zone Reduction

As previously observed, the more frequently an explosive gas or dust cloud occurs, the higher the risk and the more dangerous the zone. Therefore, it’s crucial to strive for the avoidance or reduction of the zone.

Authorities mandate a hazardous area classification, which must be documented in the Explosion Protection Document. The industrial site map, shown below, highlights the hazardous areas with shaded regions:

  • ‘G’ indicates a gas explosion hazard.
  • ‘D’ signals a dust explosion hazard.

To mitigate explosion risks, you can employ a combination of technical and organizational measures. It’s also worth noting that the lower the ATEX zone classification, the less costly the explosion-proof equipment will be. Considering the substantial cost of such equipment, prioritizing the limitation of explosive atmospheres is crucial.

A strategy like targeted ventilation can often serve as an effective and budget-friendly method for zone reduction. Our experience includes cases where ATEX zone 0 was downgraded to ATEX zone 2 solely through improved ventilation. Generally, 80% of all ATEX zones are designated as zone 2 or 22.

Practical Case of Ex Zone Reduction: Before and After

The extent of the impact of explosion-reducing measures is illustrated in the examples below.

Before: The initial situation, showing predominantly purple (ATEX zone 1) and red (ATEX zone 0) areas, indicating higher-risk zones before the implementation of safety measures.

After: The improved situation after safety measures were implemented, with areas mostly green (ATEX zone 2) and some remaining purple (ATEX zone 1), demonstrating a reduction in the level of risk.

ATEX zones, Equipment Groups and Categories

When the ATEX zone is determined, our table will assist you in selecting the appropriate equipment. ATEX equipment is classified into groups, which are further divided into categories. Let’s delve into this further.

ATEX Equipment Group I:

Equipment in this category is designed exclusively for the underground sections of mines and for surface installations at such mines that are at risk from firedamp and/or combustible dusts.

ATEX Equipment Group II:

Equipment in this category is meant for all other areas where explosive atmospheres due to gases, vapors, mists, or air/dust are present. Examples include production facilities in the food industry, chemical plants, oil & gas operations, and pharmaceutical industries, among others

Equipment Categories Within Equipment Group II:

Equipment Category 1

The equipment in this category must provide a very high level of protection as it is designed for use in Zone 0 areas (gases) or Zone 20 (dusts). Typical applications include the inside of a tank truck or the interior of a dust filter. The equipment design must offer protection, even in the rare instance of equipment-related incidents.

Furthermore, safety must remain intact even if two independent faults occur. Most equipment does not receive zone 0 approval due to the limited size of these areas and the high costs associated with engineering and certification. An example of equipment certified in this category is our explosion proof work light.

Equipment category 2

Equipment in this category is designed for use in Zone 1 (gases) or Zone 21 (dusts) and provides a high level of protection. These zones typically include areas like the manifold of a tank truck or the interior of a silo. The equipment ensures safety in the face of disturbances or faults that are expected to occur frequently.

Equipment category 3

Equipment in this category is suitable for Zone 2 (gases) or Zone 22 (dusts), where explosion protection is necessary during normal operation. Such equipment is commonly found in paint factories, warehouses, or around bag dump stations. Safety at this level is typically achieved through a non-arcing design and by limiting the equipment’s surface temperature.

Ex groups 1 and 2, including zones and respective equipment categories.

In Practice: Reading ATEX Markings

In ATEX markings, ‘G’ denotes the presence of gases, vapours, or mists, and ‘D’ signifies the presence of air/dust mixtures. Manufacturers affix ATEX markings to all equipment deemed suitable for use in ATEX Zones. Now, let’s apply our knowledge and try to interpret the real life ATEX marking presented below.

atex marking on an explosion proof wifi unit

The marking ‘Ex II G3’ on this explosion proof Wi-Fi Unit indicates its design for use in Zone 2 environments, which are at risk of gas explosions.

[Summarizing Table] and Conclusion

In conclusion, ATEX zones dictate the level of protection required for equipment in hazardous areas. Zone 0/20 requires Category 1 equipment, Zone 1/21 requires Category 2, and Zone 2/22 is for Category 3 equipment. Group 1 is for mining, group 2 is for all other gas and dust explosive atmospheres

Gas ATEX ZoneDust ATEX ZoneRemark
Zone 0Zone 20Requires Category 1 equipment
Zone 1Zone 21Requires Category 2 equipment
Zone 2Zone 22Requires Category 3 equipment
Group 1For mining (Group 1) (Category 1, 2 and 3 do not apply)
Group 2For all other gas and dust explosive atmospheres (Group 2)

We hope that we have helped to clarify some of the confusion surrounding this very important question: “Which ATEX equipment do we need in our ATEX zone?” And if you need any more information or explanation, we will be most happy to assist.

After all, Ex-Machinery has specialized in ATEX and explosion safety for well over 14 years, so please do follow our ATEX specialist Gido van Tienhoven on LinkedIn – where no ATEX question will go unanswered. We look forward to hearing from you.