There are a series of physical phenomena which concern all electrical devices in general, but which assume great importance in equipment for areas classified as hazardous for potentially explosive atmospheres. One of these phenomena is called "breathing".

The components used in contexts at risk of forming an explosive atmosphere are made with particular materials. This is particularly true in the case of plastic materials. In contexts designed to form insulation between conductors, the materials used are selected from among those that express better tracking resistance.

In Europe, the process of harmonization of regulations has opened a new phase in technological development and, to all intents and purposes, can be considered a success of the process of integration of the European Union. The birth of the EEC, the establishment of the CENELEC and CEN technical committees, the first ATEX 94/9/EC regulation and then the new ATEX 2014/34/EU regulation... let's retrace together the last steps that led to the present day have a harmonized regulatory framework at Eu

In the United States, the path that led to the development of equipment suitable for use in areas at risk of explosion has followed an almost parallel path to Europe, addressing the issue first in the mining industry and then extending it to electrical devices in the NEC. The use of still current techniques demonstrates how much the more traditional methods of protection can boast a history of reliability and safety spanning more than a century.

The most used entry systems are: entry with sealing fitting, cable entry with Ex barrier cable gland, cable entry with Ex cable gland with sealing ring. When we talk about electrical systems with electrical cable installation, entries are made using a cable gland, which can be of two types: barrier or with sealing ring.

In sites where there is a risk of the formation of an explosive atmosphere, we often find the electrical conduit in a metal protective tube (also called conduit conduit). Although it has recently been joined by more versatile armored and non-armored cable systems, with cable gland entry, its use is recommended in plants where production or use and maintenance activities can present dangerous situations for the integrity of the cables.

Sealing fittings are often considered only as secondary or minor components, but the safety of an installation with metal electrical conduits and related explosion-proof enclosures depends on them. The main function of a conduit sealing fitting is to prevent the propagation of an explosion from the inside of the ‘Ex d’ flameproof enclosure to the outside.

Explosion-proof joints are one of the basic aspects of the protection offered by an equipment or an explosion-proof enclosure. For this reason, understanding their function is a prerequisite for the correct use and the proper maintenance of all electrical devices that adopt this type of protection.

A fundamental principle of the ATEX Directive 2014/34 / EU, shared with the other Union directives, is the limitation of legislative harmonization to essential health and safety requirements of public interest. Within this legislative harmonization, a role of primary importance is played by the harmonized technical legislation and the concept of the state of the art. The ATEX Directive refers to this concept as a requirement requested of manufacturers.

Each equipment that must be installed in an ATEX classified area must have a certain level of protection, indicated in the legislation with the acronym EPL (Equipment protection Level). The level of protection is obtained by applying technical regulations that define the protection methods. There are many ways of protection, some have a historical origin, others are more recent...