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Explosion protection is a key component of safety technology in industry – especially in areas where flammable substances are used. Since small causes usually have very large effects, explosion protection requires special attention.
The EN 1127-1 standard specifies basic concepts and methods for explosion protection in explosive atmospheres. The draft prEN 1127-1:2025 revises the previous edition EN 1127-1:2019. The new standard contains numerous technical and editorial adjustments that are of central importance for explosion protection.
This article provides an overview of the most important changes, additions and new requirements in the 2025 draft standard, as well as their practical relevance.
General information on EN ISO 1127-1
EN ISO 1127-1 (Explosive atmospheres – EN ISO 1127-1 (Explosive atmospheres – Explosion protection – Part 1: Fundamentals and methodology) is one of the most frequently used standards in the field of machine safety when it comes to explosion protection issues.) is one of the most frequently used standards in the field of machine safety when it comes to explosion protection issues.
The current edition of the standard from 2019 is currently undergoing a fundamental revision, and the draft standard dated 1 August 2025 (which is open to public comment) already provides an overview of the planned changes.
When can users expect the final edition of the new EN ISO 1127-1?
If the publication process follows a similar cycle to that of the last revision, the final edition of the standard can be expected to be published in approximately two years. The draft of ÖNORM EN ISO 1127-1 was published on 1 August 2025, so users can expect the final edition in summer 2027. However, it is unclear whether this process will be accelerated due to the entry into force of the new Machinery Regulation – under certain circumstances, publication as early as the end of 2026 is conceivable.
Should the new EN ISO 1127-1 be published in the Official Journal of the European Union?
According to information on the website of the publisher CEN, the standard was created on the basis of mandates relating to the Machinery Directive 2006/42/EC, the Machinery Regulation (EU) 2023/1230 and the ATEX Directive 2014/34/EU. However, publication in the relevant EU Official Journal will take place at the earliest after publication of the final edition of the standard.
What role does the content of EN 1127-1 play in the iterative process of risk evaluation and risk reduction?
Experts in mechanical and plant engineering who are familiar with the risk assessment process according to EN ISO 12100 will quickly recognise the parallels. The iterative process for risk assessment and mitigation has been adopted unchanged from EN ISO 12100 and thus from the common basis ISO/Guide 51, and therefore offers a familiar approach.
In section 4.1 "Risk assessment, General‘ of prEN 1127:2025 clearly states that the risk assessment process for equipment (this term also includes machinery) must be carried out and documented in accordance with EN ISO 12100 and for ’non-electrical equipment" in accordance with the methodology specified in EN 15198, unless other standards are more appropriate. This reference to EN ISO 12100 is not new, but it is much more precise and comprehensive than in the 2019 edition.
Section 4.1 also sets out the increased requirements for a systematic approach and complete documentation. For example, the risk assessment process has been adopted from EN ISO 12100.
Figure 1: Risk element (from ISO/IEC Guide 51 – EN ISO 12100) for risk analysis
Does the new EN 1127-1 also cover topics specifically for operators?
The introduction notes that this standard can serve as a guide for operators of equipment, users of protective systems and components for assessing the explosion risk in the workplace (in accordance with Directive 1999/92/EC on the preparation of an explosion protection document).
These include, for example, filling stations, petrol stations, oil refineries, processing plants, chemical and pharmaceutical production facilities, and industries that use low-carbon renewable energy sources such as hydrogen, ammonia (NH₃) or methanol (CH₃OH).
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Based on the draft standard, it is clear that the revised edition of EN 1127-1 will be significantly more comprehensive, increasing from 50 pages to 70 pages. Below, we have summarised what we consider to be the most important changes in the draft document.
New terms and definitions
Chapter 3, ‘Terms and definitions’, includes many new definitions of terms that facilitate the use of this standard. The two existing definitions of “normal” and ‘increased tightness’ have been supplemented by numerous terms relating to risk assessment, analysis and evaluation, as well as intended use and foreseeable misuse.
Changes in the identification of explosion hazards (section 4.2)
In prEN 1127-1:2025, the new section 4.2.4.6 ‘“Mists”' deals with the topic of “'mists”' in explosive atmospheres. In the previous edition, this section is only mentioned briefly in section 4.4.2.c. The newly formulated section can be summarised as follows:
Figure 2: Development of the hazard event ‘mist’
Another new addition is section 4.2.4.7 ‘Hybrid mixture’. This section has also only been included as a brief note in section 4.4.2.c. A hybrid mixture is defined as a combination of flammable gas or vapour and combustible dust or combustible suspended particles.
A special feature of such mixtures is that they can behave differently from their individual components, be it gas/vapour or dust. Since the occurrence of hybrid mixtures is highly dependent on the industry, it is difficult to provide generally applicable and detailed instructions.
With regard to standards, EN IEC 60079-10-1:2021, Annex I, with information on identifying hybrid mixtures, as well as DIN/TS 31018-1 (for gases) and DIN/TS 31018-2 (for vapours) are particularly relevant. These describe how safety-relevant parameters for explosion protection are determined.
In Chapter 4.3 'Identification of ignition hazards' and 4.3.1 “General information”, the increased requirements for a systematic approach and documentation in the risk assessment process continue. In summary, the main points here are:
Examples of such devices containing flammable substances include fans, bucket elevators, pumps, compressors, air conditioning systems with flammable refrigerants, industrial vacuum cleaners, valves, gas meters, boilers, food processing or metalworking machines, and devices containing hydrogen or ammonia.
What are the practical implications of section 4.2?
Systematic hazard analysis: Manufacturers and operators must identify all potential ignition sources, not only during normal operation, but also during maintenance, cleaning and malfunctions. This increases safety and minimises unexpected risks.
Holistic approach: According to the standard, both the external environment and the interior of a device must be checked for explosive atmospheres and ignition hazards. This applies, for example, to fans, pumps or compressors that contain flammable substances.
Responsible design: Design engineers must assess at an early stage whether a device itself creates a potentially explosive atmosphere. This finding influences the selection of materials, seals and protective measures.
Categorisation and conformity: The results of this assessment are decisive for the classification of the device in accordance with the ATEX Directive 2014/34/EU and its categories, as well as for compliance with legal requirements. An incomplete analysis can lead to incorrect classification and legal risks.
Practical implementation: The standard provides clear guidelines on how to identify and assess ignition hazards. This is beneficial for documentation, certification and communication with authorities and testing institutions.
Under ‘Hazards from possible ignition sources’, the new section 5.13.2 ‘Thermal runaway of cells and batteries (lithium)’ has been added. This is a topic that has not been addressed in previous editions.
Thermal runaway is the name for a dangerous condition in lithium batteries in which internal or external influences (e.g. short circuit, overcharging or external heating) cause an uncontrolled increase in temperature in the battery. This releases chemical energy through internal short circuits, leading to rapid heating and decomposition of the cell components. In addition, combustion energy is produced by the ignition of the gases generated in the process.
The decomposition is exothermic and accelerates itself until temperatures of 800 °C to 1000 °C are reached. This produces flammable gases (e.g. hydrocarbons, CO, hydrogen) and solid particles (e.g. aluminium, copper), which can be released explosively. Ultimately, a battery cell can be ejected.
Changes in the risk reduction process (section 6)
The content of the fundamental principles in the risk reduction process (Section 6.1, b) has remained unchanged. Only the term ‘explosion protection through design measures’ has been replaced by the term ‘protection (tertiary protection measures)’.
In explosion protection, tertiary protective measures name measures that are used when the primary and secondary explosion protection measures are insufficient. In tertiary explosion protection, the effects of an explosion are therefore limited to a safe level, for example by means of explosion-proof construction, pressure relief or explosion suppression.
With regard to the replacement of flammable/combustible substances (section 6.2) with non-flammable/non-combustible substances or substances that can no longer form a hazardous explosive atmosphere, there is now a clear order of priority. This was not the case previously.
The quantity of combustible materials must be reduced to a minimum; a quantity-related regulation can be achieved, for example, by the following means:
a) Reduction of the quantity of flammable materials b) Avoidance or minimisation of releases c) Control of releases d) Prevention of the formation of an explosive atmosphere e) Collection and containment of releases
The practical implementation of these points is described in section 6.2.1.3 with a few textual changes. Depending on the plant, these changes may have individual effects.
Additional requirements for the information for use (section 7)
Here are two new examples of ATEX marking, which illustrate that the device group and category must be clearly specified in the user information. In addition, particular attention must be paid to the intended use and application limits.
Relationship between prEN 1127-1:2025 and the essential requirements of the Machinery Regulation (Annex ZB)
The table in Appendix ZB shows the relationship between prEN 1127-1 and the Machinery Regulation (EU) 2023/1230. It is clear that significantly more points in the Machinery Regulation relate to prEN 1127-1 than to the Machinery Directive 2006/42/EC. This is a clear advantage for the machine manufacturers concerned.
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The revision of the standard will lead to a significant modernisation and expansion of explosion protection requirements. On the one hand, the scope has been clarified and now also covers current technologies and substances such as lithium batteries, hydrogen systems and hybrid mixtures.
In addition, terms and definitions have been made more precise and the list of possible ignition sources and the associated protective measures has been expanded. Overall, the new 2025 version provides greater clarity, topicality and practicality without changing the fundamental character of the standard.
Posted on: 2025-09-05
Wolfgang Reich CE marking and safety expert HTL electrical engineering, specialising in power engineering (Dipl.-HTL-Ing.), 20 years of experience in CE marking, machine safety, conversion of machines, electrical engineering and explosion protection, 10 years of which at TÜV Austria and Intertek Deutschland GmbH. Chairman of the master craftsman examination commission in the Styrian Chamber of Commerce for mechatronics (automation technology and electronics).
E-Mail: wolfgang.reich@ibf-solutions.com
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