40 years of explosion protection mirrored
in the Ex-Magazine

At that time explosion protection had not been regulated exhaustively at the legal level (laws/regulations/technical rules) in Germany. Regulations referred to material-, system- and devicespecific aspects or had been "hidden" among
general safety requirements. The former included in particular the regulation on combustible liquids (VbF, original version dating back to 1960) and the explosion protection regulations (German-Federal-Land-specific) as well as mining regulations. However, the German Social Accident Insurance Institutions (also institutional legislators)
had already issued binding regulations for the entire field of explosion protection ("Explosionsschutz -Richtlinien, EX RL", today: "Explosionsschutz-Regeln”), which later became a model for the legal regulations in Europe for operation of
"Ex Plants" as well as for many European standards on non-electrical explosion protection.
Thus, further development of explosion protection remained mostly in the hands of the users (process industry) and manufacturers of electric equipment, machines and systems. In the field of electrics, explosion protection had
been regulated by the standards of the corresponding standardization organizations such as VDE, CENELEC and IEC.

The electrotechnical standards are characterised by high continuity. The applicable standard in Germany in 1974 was VDE 0170/0171, the 1944 version of which had been changed only slightly by amendments in 1957 and 1961, even if the technology itself had become more modern. The type of protection "Intrinsic safety (Ex)i / (Sch)i" was introduced in 1965. Deviations from the standard were checked by both German certification bodies PTB (German Physical and Technical Federal Institute in Braunschweig) and BVS (German Mining Test Facility in Dortmund) and certified
as special protection "s". Based on the certificates, the district government or regional mining authorities issued the approvals according to the local regulations (on the basis of the ExVO).
Comparable regulations also existed in all other countries in Europe and in the world, but only on the basis of the corresponding national standards and laws. Marketing of very high-quality and safe German products on the international market was a time- and resource-consuming task for the export-oriented manufacturers.

In 1967, IEC 79 was issued for the type of protection "Flameproof enclosure"; then IEC 79-0 and other types of protection. There was no obligation to apply it at that time. IEC publication 79-10 issued in 1972 served as a pilot project because, for the first time, it had the uniform zone classification. During the
wording of zone definitions, each term was intensively discussed and haggled over.
The work at IEC was running in parallel to the first European "harmonization" of the national standards. EN 50014-50019 (only for Ex I and EX II /Zone 1) were established in a laborious process between 1967 and 1977 by Cenelcom (later: CENELEC). These standards contained technical concepts whose origin could be clearly traced back to the French, British or German standards. While for example in Germany the cable entries were usually led into connection boxes with type of protection "e", in Great Britain they were normally flameproof and also contained isolating switches. In France certain electric cables could also be led with special cable entries directly into the flameproof contactor rooms. The synthesis of these variants in the EN standards led partially to technical solutions whose safety level did not always comply with the originally intended one.

The alignment of the European equipment standards for explosion-protected electrical equipment was supported by the first EEC directives for the optional opening of the EEC market for products which complied with the "harmonized" European standards. Harmonization was the explicit quotation of the standards in an EEC directive.
Directive 76/117/EEC provided the legal framework. The member countries were not allowed to impede the sale of products if an "approved body" had issued a "certificate of conformity" on the compliance with the harmonized
standards. The concrete application was facilitated by the Directive 79/196/EEC with the first list of harmonized standards. The Hexagon-Ex had to be used as a "distinctive community mark" on equipment and certificate.

Both EEC directives from 1977 and 1979 were integrated in 1980 into the German legal system with a comprehensive re-organization of explosion protection in Germany by the regulation on electrical installations in areas with potentially
explosive atmospheres ("ElexV"). Both type examination certificates of the German certification bodies PTB and BVS and conformity certificates from the approved bodies (INIEX/BE, DEMKO/DK, CERCHAR and LCIE/FR, BASEEFA/GB and CESI/IT) replaced the approvals according to national law of the German Federal States (Lands). PTB and BVS were nominated as approved bodies ("notified") by the diplomatic note of the permanent representative of Federal Republic of Germany at EEC.

The ElexV also included the zone definitions and references to technical codes of practice such as the guidelines for explosion protection “EX-RL” as mentioned before. In addition to the zone definitions, there was an agreement between the Federal Minister of Labour and both German certification bodies: PTB took over the certificates for Zone 0, BVS - certificates for Zone 10 (currently known as Zone 20). Both bodies committed themselves to avoid issuing any certificates for the Zones 2 and 11 (today: Zone 22).
Custom-made equipment could be checked and certified according to ElexV by specially qualified and approved experts of the users and manufacturers. Thus, these experts had virtually the status of a notified body, but only for the German market.

In the cross-border trade, explosion-protected electrical equipment at the beginning was subject to a lot of friction, and there were many attempts to protect the national market . Many controversial discussions relating to the acceptance of certified equipment took place in the HOTL (Heads of Testing Laboratories) working group of the certification bodies. This working group was organised by the EC Commission. With 8 members, the group was quite manageable: BE: INIEX (Belgium), PTB and BVS (Germany); DEMKO (Denmark), CERCHAR and LCIE (France); BASEEFA (Great Britain); CESI (Italy).
With the later expansion of the EEC, LOM (Spain), Arsenal and TÜV Vienna (Austria), VTT (Finland) and SP (Sweden) were added,, while the entry into force of the Mining directive 82/130/EEC also added, the British body HSE(M). The meetings were held on a rotating basis at the facilities of the individual members, this facilitated building up of the mutual trust and adjustment of the testing procedures. Already in 1982, the group performed a proficiency test on the reference explosion pressure determination on a flameproof motor.

Overall, HOTL has made many positive contributions to the unification of the rules of the game.
After max. 10 years, the European system of market opening for uniformly tested and labelled devices was a success story. The "Ex" has become the logo of the European explosion protection and the key to the market entry even outside the EEC. To reduce bureaucratic obstacles, HOTL introduced the component certificate for the Ex components such as terminals, cable entries, empty enclosure. It did not have any official status, but it worked and was added to Directive 94/9/EC. The HOTL members mutually agreed to accept these certificates.
A testing and certification procedure provided by the directive in case of deviation from harmonized standards ("Inspection Certificate") got under way very late, by which time the HOTL group had developed a simplified procedure for the application of non-harmonized ENs.

The system of standard harmonization by means of individual EEC directives though functioning had been too slow in view of the fast and multiple changes of the EN standards. To implement the EC initiatives for "Completing the internal
market" and for the "New approach", this system was replaced by Directive 94/9/EC with its reference to a list of standards in the Official Journal of the EU.

For the first generation of EN 50014-50020, the technology of mechanical components was oriented towards metallic materials. The testing criteria for plastic materials had to eliminate any existing concerns. The spectrum of material
tests was widely extended. Only application showed that certain material characteristics were often not available and had to be determined during elaborate test series. The requirements for prevention of dangerous electrostatic charges formed another significant obstacle.
These changes of EN 50014-020 were harmonized in 1984 as the so-called "B generation" (for group I: 1988), the letter B being added to the digit sequence of the certificate.

While the VDE standard for the apparatus of Zone 0 remained just a draft, VDE 0170/0171 Part 13 for devices of Zone 10 was published in 1986.
For Zone 11, VDE 0165 contained enough criteria to select suitable equipment from products for normal industrial applications.

Before EN 50028 was published, encapsulated devices and components had been certified in Germany as special protection "s" on the basis of internal testing rules of the certification bodies. Even with EN 50028 as a synthesis of the
test methods from the certification bodies in Europe, a test phase was necessary to gain experience especially with encapsulation materials.

During integration of EN 50014-020 into the VDE- standards in 1978, the 1st of May 1988 was defined as the date up to which the parallel application of VDE 0170/0171/1.69 was still allowed. This transitional period of 10 years seemed to be sufficient, but in the end it was not enough. Shortly before the end of this period, the German DKE committee K 241 introduced a "life-supporting" measure for the equipment designed according to the national standards.
The A102 amendment for Part 1 of VDE 0170/0171:5.78 (=EN 50014) cancelled the end of the 10-year transitional period partially, with the effect from the 1st of May 1988:
For the equipment still not covered by the harmonized standards, PTB and BVS were able to issue further national Ex s certificates. For equipment approved before 01.05.1988 or typeexamination tested equipment of Group I, BVS could certify further design modifications. Further applicability of VDE 0170:1.69 for mining was supported by a corresponding change of the Mining Regulation on Approval of Electrical Equipment. The most important definition for the users of explosion protected devices was the following statement of the standard:
"Transition to the new standards has been performed in terms of the European harmonization; it does not imply a change of the safety level."
It prevented a mandatory retrofitting of the installations in operation due to alleged rising of safety level by more recent standards.

After the German unification, the network of regulations and standards existing in the Federal Republic of Germany was imposed on the new “Laender" (Federal States). Only transitional rules remained for the previous TGL standards (“Technischen Normen, Guetevorschriften und Lieferbedingungen”) of the German Democratic Republic.
The Freiberg testing center – part of the Institute for Mining Safety – was privatised with temporary federal funding and is now known as IBExU.

For Germany, the installation standard VDE 0165 was sufficient. It specified the criteria for the
selection of Zone-2 equipment from "normal" industrial appliances which are “non-sparking in normal operation”. However, at European level a product standard seemed to be absolutely necessary.Already in 1975 the Chairman of TC31 H. G. Riddlestone warned that "on occasion, requirements for apparatus for Zone 2 become more onerous than those for Zone 1 equipment." During preparation of EN 50021:1988, the requirements went significantly beyond those
usual for VDE 0165. EN 50021 was not harmonized because the EEC Directive did not cover the apparatus of Zone 2. During revision by the IEC, concepts from the North American system with its “Division 2” classification were adopted
into IEC 60079-15.

The Directive 94/9/EC drafted according to the "New approach" brought a multitude of upheavals whose implementation entailed significant efforts and costs for the manufacturers and users. Against serious doubts, the non-electrical devices and protective systems were included in the scope. Further serious changes were:

• Establishment of equipment categories for all zones
  However, there were strong reservations against establishment of an equipment category 0 by analogy
  with Zone 0 ("Zero? C’est rien!").
• Three equipment categories for dust explosion protection
  For the proven "two-zone" system for dust (Germany: 10 and 11; GB: Y and Z; North America: Division 1 and 2), the standardization committee had developed a threezone system for dust mirroring the three Zones for gas. This has already been reflected through three equipment categories in spite of the fact that the three dust zones became mandatory in Europe only with the Directive 1999/92/EC. The threefold division of the equipment categories was adopted in 2007 by the IEC as the "Equipment Protection Levels" in IEC 60079-0.
• Adoption of the entire spectrum of equipment relevant for explosion-protected, such as protective systems (e.g. explosion pressure relief, explosion suppression), gas detection instruments, safety devices and combustion engines.
• The adoption of safety devices the safe function of which , for example had to ensure that no sources of ignition occur at a monitored equipment during normal operation and in case of faults, took place at a time of discussion on the adoption of quantifiable safety levels for the correspondingly evaluated risk classes and its  standardization.
  In particular, the users of large industrial plants with safety-critical processes experienced a difficult time. The safety technology developed on the basis of long-term experience often did not allow easy and successful assessment by means of the instruments such as SIL (IEC 61508).
  The safety equipment relevant for explosion protection was also standardized only after intensive consultations, in separate ENs for electrical and non-electrical equipment.
• Involvement of the notified bodies for the supervision of the quality management for the product manufacturing. Manufacturers and QA certifiers had to get used to this ATEX-specific overlay to the existing QA system according to ISO 9000.
  Today, one can say that the transition from optional harmonization to the accomplished Single European Market has been a success, even though there are some side effects which are not all about safety.
  For example, by now there are approximately 66 notified bodies in the EU, each of them having been accredited (if at all) and notified according to different criteria. Evaluation of the professional expertise of certification bodies is the responsibility of the member states. Improvement is expected from the so-called "New regulatory framework", which led to the adoption of the new "ATEX Directive" 2014/34/EU in 2014, it is to be applied starting from 2016.

Along with the elimination of trade barriers through the internal market in the economic sphere (it included the ATEX Directive 94/9/EC with its safety requirements for "merchandise"!), the European Union has aimed at reaching a minimum level in the social fields for all member states.
Unlike the regulations for the internal market, the individual states can go beyond their specifications in their national requirements, but they are not allowed to fall below the limits stipulated by the EU. This applies in full to the explosion protection as part of occupational health and safety..
The Directive 1999/92/EC on the "Minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres" ("User" ATEX) was adopted in 1999. This directive and the associated non-binding guide of the EU commission have to a great extent the same characteristics as the EX-RL of the German Social Accident Insurance Institutions as mentioned before. One of the most important features in it is the EUwide definition of the zones. In terms of area classification, it introduced 3 zones not only for gas but also for dust explosion hazards as it had been already discussed earlier in the standardization circles.In 2004 the IEC adopted this model
in IEC 61241-10.
In Germany, this EU directive was implemented in the national law by the Ordinance on Industrial Safety and Health (Betriebssicherheitsverordnung, BetrSichV) and to a smaller extent by the Ordinance on Hazardous Materials
(Gefahrstoffverordnung, GefahrStV). This also included a paradigm shift: Within previous German legal regulations, the requirements for the equipment had been interwoven with the requirements for the operation of (electric) systems in hazardous areas, now a strict separation was implemented: For explosion protection, the Ordinance for Explosion Protection (Explosionsschutzverordnung, ExVO) as the implementation of the ATEX Directive 94/9/EC was decisive for
the equipment starting from 2003, whereas for the operation this decisive role was taken by the BetrSichV with the GefahrStV, also from 2003. In the course of this development, the annulment of previous legal regulations such as ElexV
and VbF became necessary.Direct reference to the standards was no longer provided in the legal regulations. Important standards obtained their mandatory character from the EU Commission by way of mandated "harmonization" at the
European standardization institutions CEN and CENELEC.
Explosion protection of high quality is based on correct equipment and technology as well as on correct operation - that's not a new insight! The European directives and their corresponding national legal implementations could not "re- invent" explosion protection. However, it has brought something new: All parties concerned had to deal intensively with the issues of explosion protection.

• It has drawn the attention to the aspects which have been less noticed in the past, for example the aspects of dust explosion protection, suitability of non-electric equipment for explosion protection or electrostatics as source of ignition.
• A comprehensible representation of the followed explosion protection concept and the corresponding taken measures became mandatory ("Explosion protection document").
  A small but also important detail was now mandatory use of the warning sign at all access points to a hazardous area.
• Since then, the so-called "Ex- Plant" as a whole is subject to regular inspections by appointed expert persons or institutions. (In this way Germany went beyond the European minimum requirements.)
• Role distribution and its understanding by the manufacturers, users, authorities and testing institutions had to be reconsidered and redefined

All of this has, no doubt, contributed to raising the awareness of safety issues not only in large companies but in particular in small and medium-sized companies and, thus, to enhancing the explosion protection in general.

In Germany, the entry into force of BetrSichV made it necessary to substantiate this overall general regulation and facilitate its application in practice. This has been achieved by the government issuing new technical rules for operational safety (Technische Regeln für Betriebssicherheit, TRBS). Important sources of information for the explosion protection are, among other things, the TRBS 2152 with different parts of it and TRBS 2153.
TRBS 2152 Part 5 is currently in the last drafting phase. This TRBS takes account of the latest developments and findings for the assessment and application of process control technology in the explosion protection.

While in 1974 many types of protection such as flameproof enclosure were considered to be extensively researched and underwent only slight adjustments in the standardization, the type of protection intrinsic safety was subject to a continuous change process from the beginning on, which has often represented a challenge not only for the manufacturers.
Even if there had been tests and certifications of equipment which could not initiate an explosion due to sparks and hot spots, intrinsic safety as the type of protection was standardized in Germany only in 1965, regarded more as a guideline. There were only the types of protection (Ex)i and (Sch)i with single fault safety and a safety factor.
EN 50020 was the first to introduce in 1977 the categories "ia" and "ib", with a footnote indicating that "ia" was suitable for Zone 0.
A constant challenge for all involved parties was and still remains the maximum transmittable power with intrinsically safe electric circuits. The users required ever longer lines for monitoring of large systems and for providing electric power to as many appliances as possible. Even for lighting purposes intrinsic safety was applied as a type of protection at an early stage.
Two concepts existed for raising the power limit:

• Disconnection of the supply circuit before the interruption or short-circuit spark becomes ignition capable. This approach was published already in 1975 by Halama at the 2nd IEE conference "Electrical Safety in Hazardous Environments". The application of this concept was approved usually for category "ib" only. According to IEC 60079-11:2011 controllable semiconductors can be used for "ia" as safety shunts or, in series, for power limitation, but they cannot be used for current limitation.

A separate standard (IEC 60079-39 "Power i") is currently being drafted for a sophisticated concept of this type.

• Supply with high-frequency electric circuits whose ignition threshold values are generally higher than with direct current. Investigations of the frequency-dependent ignition threshold values were performed at PTB already before 1981, BVS took over after 1982. The corresponding limiting values were implemented in the VDE 0848 standard. After that PTB resumed working to focus on this topic.

Primarily due to highly motivated working group members and perfect strategic management in
CEN-TC 305 and its subgroups, almost the entire safety-related know-how of non-electrical explosion protection contained in e.g. EX-RL, VDI directives and investigation reports was transferred to the CEN standards. The beginning was made by the EN 1127 with the fundamentals in 1997. Actually the Official Journal of the EU lists 63 EN standards for a wide diversity of protection concepts, protective systems and substance characteristics determination.
The most important of these CEN standards will soon be published as ISO or ISO/IEC standards with worldwide applicability and, thus, can find their place in the IEC certification system. A holistic concept of explosion protection standardization ensures that ISO standards can also be created by the sub-committee 31M of IEC TC31.
A special aspect of technology transfer can be seen in some CEN standards which are only relevant for the mining industry: The specialist knowledge collected here in Germany and Europe on the firedamp protection underground has been adopted in these standards and can still be used even if the mining industry is a phase-out branch here.

At the 5th IEE conference on explosion protection Andy Owler presented its report on the planned IEC certification system for the electrical devices for hazardous areas. The first ideas for this arose from the success of the European
system with the "Ex" which has become worldwide the logo for high-quality explosion protection from Europe.
The aim was to create something similar on a global scale. Internationally established users (e.g. from the chemical and petrochemical industry) prefer to use the same plant technology everywhere, and manufacturers dislike going
through separate certification procedures in each export country.
Therefore, the starting conditions for the IEC-Ex system (first, "IECEx scheme", analogous to the CB scheme for low- voltage equipment) have been very good and a successful development can be expected.
By now, 31 countries are taking part with a total of 45 certification bodies. Due to legal matters, the certificates usually cannot be applied directly as an "approval" in the individual countries, but have to be accepted by a national or regional IECEx certification body; however, this does not change anything about the uniform safety-related standards.
IECEx certificates are given particular importance by the recognition of the IECEx system as a model for legal rules of explosion protection by the UNECE (United Nations Economic Commission for Europe). IECEx: "Not a passport yet,
but already a pass permit.", this is how the Chairman of IEC-Ex Thorsten Arnhold (R. STAHL) summarized it.

In North America, explosion protection has developed historically and with regard to the standards differently from Europe and the rest of the world; this refers in particular to the installation technology and classification of the hazardous areas. The Ex Magazine discussed the American explosion protection for the first time in 1979.
Since then it has also become a recurrent subject of the Ex Magazine.
An important milestone in the approximation of the NEC (National Electrical Code) of the USA and the IEC standards for explosion protection was the modification of NEC in the year 1996:
The paragraph 505 was adopted into the standard NFPA70. This paragraph allowed for the classification of gas explosion hazardous areas and for the definition of equipment requirements according to the zone system and enabled approval according to the IEC-adapted US standard (AEx). Up to that time, only classification into Class and Division had been used.

Adoption of three dust zones in the NEC followed with its 2005 version. In Canada this approximation to IEC has progressed much further than in the USA. In Canada, most systems are nowadays classified according to the zone system and cable installation instead of lines in metal pipes (conduits) is widely used in new systems.
Due to increasing internationalization of the user industry and manufacturers of explosion protected products, harmonization is in the best interest of all parties involved. However, some traditional American manufacturers of explosion protected products see their future turnover at risk.
Leading manufacturers have nowadays products in their portfolio which can be used both in the USA and Canada and in the rest of the world, i.e. globally applicable products. It still requires multiple certification today, but it gives the internationally operating plant engineers and equipment manufacturers the chance to offer the same basic technical design worldwide without significant national modifications.
The progress of this harmonization becomes apparent by the participation of the North American experts and institutions in the IEC standardization, the IECEx system, as well as by the latest developments as regards the acceptance
of IEC technology in the area of oil and gas production (offshore and onshore). This is commented on in a separate article in this Ex Magazine.

Actually, there are only two fields which stand in the way of worldwide harmonization of explosion protection. First of all, the different nature of the North American standards, especially in the USA, and, secondly, the national and regional legal regulations for the formal conformity certification of the products. The solution of the NEC/IEC problem can only be achieved by gradual adaptation of the standards. This will take many years. The solution of the conformity assessment procedure requires legislative amendment of the corresponding legislature in the countries and regions. In Europe this is only possible by way of the EU Commission. The road to making the IEC system consistently applicable worldwide is still long, but it is worth the effort to pursue it and to continue working on both main problems from all sides, standardization organizations, legislatures, WTO, the UN and the EU, etc.

The story of 40 years of explosion protection described here does not claim to be complete. Nevertheless, an attempt has been made to show significant development milestones, and all developments mentioned have found their
way into the contributions and technical articles of the Ex Magazine from a wide range of points of view, supplemented with topics from the regularly organized "Ex Forums" of R. STAHL over several decades.
We wish the Ex Magazine to remain also for the next 40 years THE major professional medium in the area of explosion protection and the communication medium for experts from all involved sectors. The harmonization of the regulations and the achievement of a consistently high safety level worldwide are an important issue.
We hope that it will not take another 40 years to reach this goal.
Competence and experience along with the insight on where the limits of expertise are important for maintaining a high safety level and preventing serious explosion accidents.
The continuous passing on of knowledge and updating of available and newly gained specialist knowledge are the guarantees for preserving and improving the safety level.
We call on all parties involved to continue working on it.