Challenges of the Services

in Explosion Protection
by Ulrich Johannsmeyer and Uwe Klausmeyer

 Challenges of the Services in Explosion Protection (500 kB)


Hazardous areas occur in many industrial or commercial plants where combustible material is handled. In these areas electric motors, drive pumps, ventilators and conveyor equipment; thermostats and pressure switches control processes, and electrical heatings warm up products. As (electrical and non-electrical) devices, which are not protected against explosion, can turn into an ignition source, their application in hazardous areas would constitute a substantial risk for employees, production facilities and the environment. The European directives 94/9/EC and 1999/92/ EC have been a common basis for explosion protection for a long time. Additionally, European standards have been and are being created in order to be able to fulfil the ›fundamental safety and health requirements‹ of the ATEX directive 94/9/EC, with these harmonized standards, in order to make use of the so-called presumption of conformity with the requirements.
The division of hazardous areas into zones is for the gases/vapours and dusts part of the in-plant explosion protection requirements for the working environment according to the directive 1999/92/EC. The risk assessment and the derived safety instructions must be written down in an explosion protection document. The measures taken (technical, staff, organisational) ensure that the minimum safety requirements for work stations regarding equipment, installation, staff and organization are met according to the requirements of the directive 1999/92/EC.

Directive 9/94/EC (ATEX directive)

For placing devices and protective systems on the market, the directive 94/9/EC applies; in Germany, this directive has been implemented via the Equipment and Product Safety Act (GPSG). Since 1 July 2003, relevant products can only be placed in the market, freely dealt and operated within the EU according to their intended design and purpose, if they comply with the directive 94/9/EC (and other relevant legislation). The directive points out that the basic requirements for safety and other relevant attributes, which guarantee a high degree of protection, have to be defined in order to eliminate obstacles to trade by means of the ›new approach‹ that was declared by the Council resolution of 7 May 1985. These ›fundamental safety and health requirements‹ are listed in Annex II to the directive 94/9/EC. They refer to:

  • potential ignition sources of devices intended for use in hazardous areas, 
  • autonomous protective systems which basically serve to stop an explosion immediately after its start and/or to limit the effects of the explosion flames and pressures,
  • safety devices intended to contribute to the safe operation of the named equipment regarding its ignition sources and to the safe operation of autonomous protective systems,
  • components without autonomous function which are of fundamental importance for the safe operation of the named equipment or autonomous protective systems.

For the first time, the directive 94/9/EC even contains harmonized requirements for non-electrical devices, intended for use in areas where explosion hazards exist due to dust formation, as well as for the use in protective systems. Safety devices which are intended for use outside hazardous atmospheres, but which are necessary for the safe operation of devices or protective systems regarding the risks of explosion, are included as well. This is a significant widening of the scope of application in comparison to the earlier national regulations regarding devices and systems for intended use in hazardous areas.

Issuing EC declarations of conformity according to the EC directive 94/9/EC after the edition of new standards

According to the 11th ordinance on the Equipment and Product Safety Act (Ordinance on Explosion Protection) on the basis of the EC directive 94/9/EC, Appendix II, German law requires that technical knowledge, which changes quickly, must be applied immediately and as far as possible.
For this reason, the standardisation organisations CENELEC, and in the future even CEN, usually draw back standards after a transition period of three years when a new edition has been published. After this period, new EC prototype test certificates are issued on the basis of the recent edition of the standards. It is assumed that even the latest (safety) technical knowledge is represented in these recent editions. The modifications shall be listed and evaluated in the preface of a new edition of the standards. If the evaluation result is ›The safety-oriented knowledge has changed significantly due to the the new edition‹, the concerned products must be subject to a review and, if necessary, to a re-certification (addition to the current or edition of a new EC prototype test certificate) within the transition period (until the old review is drawn back).
The manufacturer alone is responsible for performance and for evaluating if a certain product is concerned by a change in the standards. The reason for this is the so-called ›New Approach‹ of the European Union which emphasizes the manufacturer's responsibility for his product. The binding document is the EC declaration of conformity by which the manufacturer declares conformity with the essential safety and health requirements of the directive 94/9/EC, and with other concerned EC directives, if applicable.
After the publication of a new standard edition, the manufacturer checks if his product is affected by the changes. This procedure is facilitated by the list of changes in the preface of the new edition. The following problem may occur: The EC prototype test certificate is based on the old standard, but the EC declaration of conformity shall be completed with regard to the new edition of standards. The problem can be solved by one of the following scenarios where the PTB (German Federal Technical Institute) will play a supporting role:

Scenario 1:
The manufacturer finds that his product is not affected by the changes in the new edition of the standard. This comprises cases where the changed requirements are not relevant for the product or in the case of extensions.


  • The manufacturer changes the EC declaration of conformity and takes the new editions of the standards as a basis,
  • At the same time, he continues to refer to the EC prototype test certificate according to the old editions. If acceptance problems should occur on the end user's side, the manufacturer can offer the assertion of a notified body regarding his specific product (up to an addition to the EC type-examination certificate).

Scenario 2:
The manufacturer finds that his product is only minimally (e.g. formally) affected by the changes.


  • The requested changes do not leed to a modification of the product's design. A test could have been implemented which can be verified easily. Thus, the compliance with new criteria is evident,
  • The manufacturer documents the compliance with the new requirements and adds them to the documentation belonging to his EC declaration of conformity,
  • He changes the EC declaration of conformity and takes the new editions of the standards as a basis. At the same time, he continues to refer to the EC type-examination certificate according to the old editions,
  • For some standard cases, the PTB publishes (in agreement with the AK Ex from ZVEI) information leaflets and check lists which support the manufacturer in this scenario,
  • The PTB allows the manufacturer to put the new marking on products even without the new EC type-examination certificate, if the manufacturer informs the PTB in writing. After a formal check, the PTB can object to the change of the marking, if necessary. No technical evaluation is carried out.

Scenario 3:
The manufacturer finds that his product is affected by the changes. He needs to detect a requirement or a test by which the design of the product is slightly changed.


  • The manufacturer sends the documentation of the effected tests or of the tests to be carried out at the PTB as well as the technical documentation with the minor changes to the PTB with a request for its opinion or for completion, 
  • After a positive appraisal of the tests and documentation, the PTB will write a letter which confirms the reliability, or, upon request, the PTB will write an amendment to the corresponding EC type-examination certificate (in case of acceptance problems),
  • At the same time, he continues to refer to the EC type-examination certificate according to the old editions.

Scenario 4:
The manufacturer finds that his product is affected and that the changes are substantial (see Annex ZY of the new European standard).


  • The manufacturer requests an amendment to the current EC prototype test certificate based on the new editions of the standards or he requests a new EC prototype test certificate,
  • He changes the EC declaration of conformity and takes the new editions of the standards as a basis. At the same time, he refers to the changed or new EC type-examination certificate.

The international market in explosion protection

Even in explosion protection, the importance of the international market is constantly increasing. The German industry has an above average dependency on the global trade with devices and engineering services; the basis of this trade should preferably be completely harmonized with IEC/ISO standards, certification procedures and federal regulations. The customers for explosion-protected devices are mainly part of the chemical, oil and gas or pharmaceutical industry. For the global market, manufacturers need, aside from European certificates (EC prototype test certificate, information about the assessment of the quality assurance in production), a certificate according to the IECEx system as well as a UL (Underwriters Laboratories) or an FM (Factory Mutual) approval. It will take some time before the vision of a worldwide valid certificate becomes reality. Therefore, the PTB has been qualified to issue ATEX and IECEx certificates. Thanks to the partnership with UL and their experts on the PTB site, the PTB continues to provide manufacturers with the possibility of a facilitated entry to the US market (see even ›New developments in the cooperation of the PTB with other certification bodies‹).

The role of the PTB in explosion protection

Questions of the public technical safety - a part of which explosion protection is - are the responsibility of the state because they are a part of public service. The state is thus responsible for the correct accomplishment of this mission. In the field of explosion protection, the German Federal Technical Institute (PTB) and the Federal Institute for Material Research and Testing (BAM) execute this responsibility according to a mutually agreed division of work.
A joint body of BAM and PTB in the shape of the current steering committee ›Physico-chemical safety technology‹ has proven to be a very efficient solution for the performance of the state's functions in explosion protection. The area of activities include giving advice to the Federal Government, asserting German interests in international and European standardization organisations and other committees, and providing services and research.
PTB and BAM are engaged in pre-standardization and application-oriented fundamental research, they develop standards for the benefit of the German industry and to maintain the level of safety in explosion protection. In order to facilitate exports for manufacturers, the PTB enters into international agreements with other notified bodies (amongst others with the USA, Japan, China), strongly supports the international IECEx system (testing and certification scheme), and additionally, contributes to the international knowledge transfer via presentations and committee work. An important task for the PTB is to provide testing capacities for service tasks. This means that the PTB needs to act as ›notified body‹ according to the European directives.
Therefore, the testing competence of the PTB in the area of explosion protection is a precondition for a sufficient reputation in order to be able to act internationally and in the interests of the German economy. Nevertheless, it is the PTB's strategy to exclusively perform tests without routine nature and tests for which there are no pre-conditions for a comparable task fulfillment by other notified bodies. Normally, complex systems are tested and evaluated for which the research field of the PTB and the cooperation with the BAM are valuable.
As ›notified body‹, the PTB competes with notified bodies from other member states on the European domestic market. The rates raised by the PTB are the result of internal costs and performance accounting; they are dimensioned in such a way that they enable a high degree of cost recovery. The level of costs guarantees that the PTB does not gain benefits from the market via the price. The high demand for the testing services of the PTB is mostly to be seen in the fact that their certificates are regarded with a high level of trust - not least due to its great technical expertise and economical independence.
The work of the PTB in important national and international regulatory committees is essential with regard to the described range of tasks, as the PTB is able to act neutrally and as an independent partner. Thus, preferentially coordinating functions are aspired, as e.g. the planning and organisation of inter-laboratory comparisons or the setup of knowledge pools (Ex Service etc.).
The trend is moving towards more personal responsibility of the industry, but with regards to industrial safety technology. The deregulation only works if a neutral and professionally competent body, participates and mediates between state and industry. The industry, as well as the concerned ministries BMWi/BMAS (German Ministry of Economics and Technology/German Ministry of Labour and Social Affairs), find this function very helpful.

Approval of manufacturer QM systems

For the conformity assessment, the modules of the quality assurance in the production phase are a core element of the new conception. In cases where the directive 94/9/EC requires a type test, an additional quality assurance module is necessary, graduated according to the categories, i.e. according to the safety level of the product. For category 1 devices (zone 0 or 20) and for protective systems, the module ›QS production‹ is required. Alternatively, a test of the product may be performed by the notified body itself, but this should remain a rare exception due to costs. The same applies for the EC routine test which would be applicable to all categories and which is probably intended for complex one-offs. In the Annexes IV and VII of the directive, it is accordingly requested for the QM acceptance that the notified body evaluates the QM system.
This and other requirements are designed such that a general QM system certificate according to ISO 9000 is not sufficient, but that a product specific or directive specific evaluation according to EN 13980 or, in the future, according to IEC/ISO 80079-34 is necessary. Within the PTB, the following principle applies:
The ex-auditor is an expert for explosion protection for certain ignition protection types or product groups and has been trained for the evaluation of QA systems. Generally, a QA system can be evaluated by experts of the PTB alone; an extension of the activities in the sense of deregulation is not desirable in a market which already has a lot of competent providers. Therefore, a current ISO 9000 certificate of a notified body is required.
The manufacturer receives notification about the directive specific acceptance of the QA system. The limitation of the acceptance to three years corresponds to the usual procedure for QA system certifications. Within the three years, a surveillance audit will be performed. The directive specific QM acceptance even serves as a basis for the IECEx system, which requires a QAR (Quality Assessment Report) that will be published on the internet with its most important data.

The trend in the manufacturing companies moves progressively towards non-German production sites. Additionally, the manufacturing of substantial parts of devices by other companies (extended work bench) can be seen more frequently.
The PTB adapts to this by means of different strategies:

  • working with external auditors (e.g. China, Far East) with the same demands that are made towards PTB employees,
  • matrix certification for manufacturers with several production sites, but with a consistent QM system,
  • audits of suppliers who produce important assemblies or components for the explosion protection.

Comparative measurements between the notified bodies according to ATEX and the IECEx testing laboratories

The convergence process within the standardization has to be accompanied regarding the sustainable implementation in the practice of measuring, testing and evaluating activities by means of a direct communication between the notified bodies. Therefore, in 2008, an extensive systematical program with comparative measurements between the notified bodies was planned and started for the very first time worldwide under the direction of the PTB. At the same time, a reference QM manual (ISO/IEC 17025, 17065) shall be generated so that, in the future, all notified bodies will be able to check and certify devices according to the same rules.
The PTB explosion protection departments will have to take on the role of the worldwide coordinator or the function of a reference laboratory to a larger extent. The program for comparative measurements begins with the measured values for explosion pressure (ignition protection type explosion-proof enclosure) and spark ignition (›i‹ type of protection). Here, especially prepared test items are sent to 41 notified bodies all over the world at the same time. In this process, rules have to be developed applying the ISO/IEC 17043 ›Proficiency Testing‹ to the explosion protection programs,as well as to the development of laboratory standards for the return of the measured values for explosion pressure and ignition thresholds of intrinsic safety. The medium term target is to make the participation in the Proficiency Testing Programs a binding condition for the issuance of IECEx certificates at least within the IECEx system. First results from the running comparative measurements where expected for the beginning of 2011.

New developments in the cooperation of the PTB with other certification bodies

Particularly with questions of safety, competence centres work together internationally with great motivation in order to exchange their experiences within the meaning of an optimum protection of the population. Therefore, the scientific technical knowledge in the professional area of explosion protection is no longer documented in national, but in international ISO and IEC standards. The regulations are applied all over the world, amongst other things for the implementation of conformity assessments at explosion-protected devices. In order to guarantee the uniformity of the daily applications in more than 50 laboratories worldwide, all laboratories are interested in close cooperation. Therefore, Underwriters Laboratories Inc. (UL) and the PTB have decided to let some of their experts work together as a working group on the PTB site. Mainly the conformity assessments on the basis of the standard group of the IEC 60079-0 are performed in joint teams. The UL experts also treat conformity assessments according to US American standards (NEC article 500/Divison 1 and 2, NEC article 505/Zone, Class I, II and III). German manufacturers can now, thanks to the close cooperation of UL and PTB, obtain approvals for the North American market as well as for the European domestic market. This is a considerable simplification of the approval process for the most important markets. UL and PTB will monitor the success of their close cooperation by means of customer questionnaires and, when the response is positive, they will extend their cooperation. Other explosion protection competence centres are welcome to join this organisational model.

Unchanged reprint from PTB-Mitteilungen 121 (2011, book 1)