Zone classification in explosion protection is a key foundation for the safe use of equipment in potentially explosive atmospheres. This overview addresses the most important questions regarding ATEX zones, the applicable ATEX regulations, and the technical basis.
ATEX refers to the European regulations governing equipment and protective systems used in potentially explosive atmospheres. The goal is to prevent potential ignition sources and ensure a high level of safety for people and equipment. The zone classification system categorizes potentially explosive atmospheres based on how frequently and for how long an explosive atmosphere may occur. It forms the basis for selecting suitable equipment and protective systems. The central legal basis for manufacturers is Directive 2014/34/EU (ATEX). It establishes the essential health and safety requirements for equipment and protective systems used in potentially explosive atmospheres. Technical implementation is based on harmonized European standards, which define requirements for the design, testing, marking, and documentation of ATEX products.
Potentially explosive zones are areas where an explosive atmosphere consisting of air and flammable gases, vapors, or mists may occur. These zones are classified based on the frequency and duration of the occurrence of such explosive atmospheres.
Zone 0
In Zone 0, an explosive atmosphere is present continuously, over long periods of time, or frequently. Therefore, the highest requirements apply to the equipment used here.
As shown in this diagram: Zone 0 is typically found only inside containers or similar enclosures.
Zone 1
In Zone 1, an explosive atmosphere may occur occasionally during normal operation. The requirements for the equipment used are correspondingly high.
Zone 2
In Zone 2, an explosive atmosphere normally does not occur during normal operation, or occurs only rarely and then only for a short time. The requirements here are the least stringent among the gas zones.
Devices are classified into the individual ATEX zones based on their device category according to ATEX 2014/34/EU and the corresponding Equipment Protection Level (EPL).
In Zone 0 areas, only Category 1G devices with protection level Ga may be used.
In Zone 1, Category 1G (Ga) and Category 2G (Gb) devices are permitted.
In Zone 2, devices of Category 1G (Ga), Category 2G (Gb), and Category 3G (Gc) may be used.
As a general rule: The higher the hazard level of a zone, the higher the requirements for protection against effective ignition sources—and thus for the devices used.
EPL IEC 60067-0 | Equipment Category 2014/34/EU | Zones | Ex-atmosphere | Prevention of Effective Ignition Sources |
Gc | 3G | 2 | rarely/briefly | during normal operation |
Gb | 2G | 1, 2 | occasionally | even in the case of normal malfunctions |
Ga | 1G | 0, 1, 2 | constantly or frequently | even in the case of rare malfunctions |
The ATEX marking indicates the potentially explosive atmospheres for which a device is approved and the protective measures taken against effective ignition sources.
The marking II 2G Ex h IIC T4 Gb is interpreted as follows:
Types of ignition protection are technical measures designed to prevent ignitionsources from becoming active in potentially explosive atmospheres. A distinction is made between mechanical and electrical types. Mechanical types of protection are governed by DIN EN ISO 80079-36/-37. The most important designation is the basic designation “h”, which includes the types of protection “c” for structural safety, “b” for ignition source monitoring, and “k” for liquid encapsulation. Electrical types of protection are governed by EN 60079. For gases, there are various protection principles: “e” denotes increased safety; “d” stands for pressure-resistant; “ia,” “ib,” and “ic” denote intrinsic safety; “ma,” “mb,” and “mc” denote resin encapsulation; “o” denotes oil encapsulation; “pv”, “px”, “py”, and “pz” denote pressure-resistant encapsulation; and “q” denotes sand encapsulation.
There are 3 gas groups. Group I is found in mining, and a typical gas is methane. Group II is found in other industries and is subdivided into IIA, IIB, and IIC.
Group III
Equipment for areas at risk of dust explosions.
The temperature class specifies the maximum permissible surface temperature of a device during operation. It ensures that the device’s surface temperature always remains below the ignition temperature of the existing explosive atmosphere.
The lower the permissible temperature of a substance, the higher the requirements for the device used.
The temperature classes are divided into six levels:
Temperature classes T1 through T6 apply only to gases, vapors, and mists (Equipment Group II).
The “Ex” marking indicates that a device can be used in potentially explosive atmospheres and meets the requirements of the relevant explosion protection directive.
An ATEX zone refers to areas where an explosive atmosphere consisting of air and flammable gases, vapors, or mists may occur. The classification is based on the frequency and duration of the occurrence of this explosive atmosphere.
Zones are classified as part of a risk assessment based on the gases, vapors, mists, and dusts present, and according to the likelihood of an explosive atmosphere occurring. Typical zones are 0, 1, and 2.
The marking indicates that the device is suitable for use outside of mining (device group “II”). The device category “2G” indicates that the device can be used in areas where an explosive atmosphere may occasionally occur. “Ex” designates a device for use in potentially explosive atmospheres in accordance with the requirements of the relevant explosion protection standards. “h” describes the type of protection for non-electrical devices according to current standards. “IIC” refers to the gas group with the highest requirements within equipment group II. Typical substances in this group include hydrogen and acetylene. “T4” denotes the temperature class with a maximum surface temperature of the device of 135°C. “Gb” is the Equipment Protection Level, which confirms a high level of safety.
Zone 0: An explosive atmosphere is present continuously, over long periods of time, or frequently
Zone 1: An explosive atmosphere may occur occasionally during normal operation
Zone 2: An explosive atmosphere does not normally occur during normal operation, or occurs only rarely and then only briefly
The Equipment Protection Level (EPL) describes the device's level of protection:
Ga: Very high level of protection, suitable for Zones 0, 1, and 2
Gb: High level of protection, suitable for Zones 1 and 2
Gc: Enhanced level of protection, suitable for Zone 2
The temperature class specifies the maximum permissible surface temperature of a device during operation. The surface of the device must never exceed the temperature specified by the applicable temperature class. The lower the permissible temperature of a material, the more stringent the requirements for the device used.
For Zone 1, Category 1G (EPL Ga) and Category 2G (EPL Gb) devices are approved.
