ATEX standard and regulation - Explosive Atmospheres

The ATEX regulation (ATmosphères EXplosives) is a European standard that requires all directors of establishments to control the risks related to the explosion of these atmospheres. It is the result of two European directives that detail the obligations of manufacturers and users of equipment in hazardous atmospheres. This concerns the directive 2014/34/EU of February 26, 2014 or ATEX 95 for equipment intended for use in explosive areas and the directive 1999/92/EC of December 16, 1999 or ATEX 137 for the safety of workers.

ATEX Zone Definitions:

In accordance with ATEX 95 and 137 standards, an assessment of the explosion risk in the company is necessary to allow the identification of all potentially dangerous areas (ATEX zones).


ATEX zone category


Gas & Vapor



Area containing explosive gas/air (or dust) mixture permanently or for a long time




Area in which an explosive gas/air (or dust) mixture is likely to occur in normal plant operation (occasional risk)




Area in which an explosive gas/air (or dust) mixture is not likely to occur in normal plant operation (equipment malfunction)



ATEX equipment marking

Since July 1, 2003, any new equipment installed must meet the requirements of the 94/9/CE directive. This directive concerns the conformity of the installation of new equipment in its industrial environment. The marking indicating the conformity of this equipment is divided into several parts:


Reference code

















The first figure (1) indicates the place of use: I for mines, II for surface industries such as chemical and petrochemical.

The second figure (2) indicates the category of the concerned area: 1 for areas 0 and 20, 2 for areas 1 and 21, 3 for areas 2 and 22.

The third figure (3) indicates the type of area: G for gas or vapor areas, D for dust areas.

The fourth figure (4) indicates the standard to which the equipment conforms: E for CENELEC, Ex for IEC (international).

The fifth figure (5) indicates the type of safety: d for explosion-proof, e for increased safety, ia or ib for intrinsic safety.

The sixth figure (6) indicates the reference gas (for gas zones): I for methane, IIA for propane, IIB for ethylene, IIC for hydrogen and acetylene

Finally, the last figure (7) indicates the maximum surface temperature: T1 = 450 °C, T2 = 300 °C, T3 := 200 °C, T4 = 135 °C, T5 = 100 °C, T6 = 85 °C

The marking of the above example (table) corresponds therefore to an equipment intended for a surface industry, for zone 0 (gas), meeting the CENELEC and IEC standards, explosion-proof, reference gas ethylene for a maximum surface temperature of 85°C

In an explosive area, portable gas detectors, fixed detectors, optical flame detectors or sirens and alarm signals must be ATEX certified for optimal protection and to prevent any danger in the environment.