In the second half of the 20th century, in many industrial and developing countries, electrical equipment suitable for use in potentially explosive atmospheres was subject to different legislation than that concerning general industrial device. The procedure for placing an industrial device on the market usually consisted of the manufacturer's declaration of conformity to current legislation, which assumed responsibility for it. In the specific case of devices for areas classified as at risk of explosion, administrative bodies were appointed by the government of the States which guaranteed compliance with a standard as a third party with respect to the manufacturer. This approach was present in both Europe and the UK.

The European Economic Community, briefly referred to as the EEC, saw its establishment with the treaties of Rome in 1957 thanks to the founding countries: Italy, France, Belgium, Holland, Luxembourg, and Germany. In the following decades, the six initial members were joined by other nations reaching the current 27 [1].

The EEC, through the signing of numerous amending treaties, assumed the current structure of the European Union with the Treaty of Lisbon of 2007. 

The initial purpose of the European economic community was to eliminate the obstacles to the free exchange of goods between the member countries. In the sector of equipment suitable for use in potentially explosive atmospheres, in addition to duties and other instruments of an economic nature, the diversity of national technical legislations constituted a barrier.

With a view to bringing national standards closer together and then subsequently replacing them with a common scheme, the European bodies indicated for standardization were CENELEC for the electrical part and CEN for the mechanical part. In different countries, the protection methods used and developed starting from mining applications were based on common concepts such as explosion containment (Ex-d), segregation (Ex-p, Ex-o, Ex-q) and energy limitation (Ex-i).

The technical committees CENELEC/TC31 and CEN/TC305 were given the task of examining the differences between national regulations for equipment suitable for use in potentially explosive atmospheres.

Not an easy process given that, even if the basic concepts were the same, the different constructive philosophies were often hidden in the details. As an example, in Germany the entry of the cable into explosion-proof enclosures was via increased safety connection enclosures. In Great Britain the explosion proof system was used while in France special cable entries could be used directly in the explosion proof enclosures.

Equally difficult was finding the common ground in the classification of plant zones, a process that began with the IEC 79-10 published in 1972. In the decade between 1967 and 1977, the European standards for sector equipment saw the light with the publication of the series of standards EN 50014-50019.

With the new millennium we have definitively entered the new approach of European directives. On June 30th 2003, Directive 94/9/EC [2] came into force for equipment, while on July, 1st 2006, directive 1999/92/EC [3] became mandatory for plants classified as at risk of explosion.

Finally, to get to the present day, the directive with code 2014/34/EU, the new ATEX directive currently in force for equipment, should be mentioned. On the regulatory side, in the early 2000s the series of EN50014…EN50039 standards gave way to the EN60079-… standards of IEC derivation [4].

Simultaneously with the updating of the equipment to the new regulatory standards, the first part of the acronym of the protection mode changed from EEx - to Ex- on the equipment plates. [5]

In Europe, the process of harmonisation 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.

Following a similar path, the IECEx scheme was born which would like to extend the principle of regulatory harmonisation on a larger scale, involving the whole world.IECEx scheme is accepted only in some countries but it represents an important source of inspiration even where there is a specific national standard.

Notes and bibliographical references:

[1] the number is updated over the years

[2] known to most as the ATEX Equipment Directive

[3] known to most as the ATEX directive on workplaces, in this directive there is the concept of classification in zones of the different areas of the plant

[4] the latest standards of this series, coded EN 50018, EN 50017 and EN 50015, ceased the presumption of conformity in 2010, see: Official Journal of the European Union C20/16

[5] EN 50014-1998                         27.5 c)