Last edit: 26/05/2026
The IEC 60079-1 standard defines one of the most widely used protection methods within the ATEX framework for electrical equipment installed in the presence of flammable gases or vapours: the Ex d method, flameproof enclosure protection.
This approach is based on the principle that the equipment is contained within an enclosure designed to withstand a potential internal explosion and to prevent flame propagation to the external environment, thereby avoiding ignition transfer to the surrounding atmosphere.
Ex d protection does not eliminate the risk of ignition within the equipment but rather controls and contains it. Specifically, the enclosure is designed to withstand the pressure generated by an internal explosion, prevent its transmission to the outside, and ensure that ignition of the surrounding atmosphere does not occur. This requires enclosures made with materials and construction solutions capable of ensuring high mechanical strength and long-term stability, even under severe operating conditions.
Another key aspect of this type of protection is the role of enclosure joints, which are designed to allow the controlled release of gases generated by an internal explosion, cooling them and thereby preventing them from igniting the external atmosphere.
Ex d protection is part of the broader IEC 60079 series, which covers the various aspects of safety for equipment used in explosive atmospheres. Within this framework, IEC 60079-1 defines the specific requirements for the design and construction of flameproof enclosures, while other standards in the series address complementary aspects such as general requirements (IEC 60079-0), installation (IEC 60079-14), and maintenance (IEC 60079-17). The performance of Ex d enclosures is verified through specific tests required by the technical standard, which assess the enclosure’s ability to withstand an internal explosion and prevent its propagation to the external environment.
Applications and Scope of Use
The Ex d method is used for explosive atmospheres caused by gases and is applicable, depending on the level of protection, to the following zones:
- Zone 1: typically with protection level EPL Gb (Ex db)
- Zone 2: typically with protection level EPL Gc (Ex dc).
With the evolution of standards, higher protection levels (Ex da) have also been introduced, which under specific conditions allow use in Zone 0, although such applications remain limited to particular types of equipment.
Ex d equipment is widely used in industries such as chemical and petrochemical plants, oil & gas, and process facilities. Typical examples include motors, electrical panels, junction boxes, and equipment with potential internal ignition sources.
It is important to note that the Ex d method is specific to explosive atmospheres caused by gases and vapours, whereas for combustible dusts, the equivalent protection method is Ex t, as defined in IEC 60079-31 and IEC 61241-1.