he standard EN ISO 13855 has been essential for many years whenever safety distances for light curtains, laser scanners, pressure-sensitive mats, two-hand controls or interlocking guards need to be determined.
At the end of 2024, ISO published the 3rd edition as ISO 13855:2024; in 2025 the German version DIN EN ISO 13855:2025-10 followed and replaced the 2010 edition.
If you look at the new text, you quickly notice: the page count has almost doubled – from roughly 50 to nearly 100 pages. But in terms of practical content, surprisingly little has really changed.
1. Brief history: from EN 999 to EN ISO 13855
Historically, ISO 13855 replaced the older EN 999 (positioning of non-separating guards) in the early 2000s. As EN ISO 13855:2010 it was then harmonised in Europe and listed in the Official Journal for the Machinery Directive.
The 2010 edition defined, in essence:
- how safety distances are calculated from approach speed K and total stopping/reaction time T,
- how different approaches (direct, indirect, climbing over / crawling under) must be taken into account,
- and how ESPE (light curtains, scanners), pressure-sensitive devices, two-hand controls and interlocking guards must be positioned.
This basic framework remains in place in the new edition.
2. Why a new edition at all?
Officially, ISO 13855:2024 is meant to update the standard to the current state of the art: mobile applications, scanner fields, more complex installations, higher expectations regarding documentation and alignment with the “safety ecosystem” (12100, 14119 etc.).
However, a closer look shows that many of the “changes” are mainly:
- more verbose descriptions of the methodology,
- new or re-arranged sub-clauses,
- additional examples and annexes.
For typical stationary applications – light curtain in front of a press, pressure-sensitive mat in front of a robot cell – the calculated distances change very little. It is fair to ask whether such a moderate change in substance really required almost doubling the number of pages.
3. What stays the same?
For most practical use cases, the following still holds:
- The safety distance S is derived from an approach speed K, the overall system reaction time T, and additional allowances for reachability and tolerances.
- Typical K values (hand/arm movement vs. walking speed) are essentially unchanged; they are simply explained and allocated more clearly to the different approach scenarios.
- The separation between EN ISO 13857 (fixed guards and minimum gaps) and EN ISO 13855 (ESPE, two-hand controls, guards with interlocking etc.) remains as before.
In other words: if your calculations were sound under the 2010 edition, you will obtain very similar distances with the 2024 edition for many machines.
4. What is genuinely new and relevant?
Despite all the criticism, there are a few areas where the new standard does add real value.
4.1 New title, clearer scope
The title is now “Positioning of safeguards with respect to the approach of the human body” – no longer just “approach speeds of body parts”.
In the scope, the standard explicitly states that it specifies requirements for:
- detection zones of electro-sensitive protective equipment and pressure-sensitive mats/floors,
- the positioning of two-hand controls and single control devices,
- and the positioning of interlocking guards.
New in comparison to the old edition is the explicit inclusion of safety-related manual control devices (SRMCD) – such as enabling devices – including cases where they are intended to be operated within the safeguarded space.
4.2 Dynamic separation distance
What really is new is the more systematic treatment of dynamic separation distances.
The standard now explicitly addresses situations where the hazard itself moves – for example driverless transport systems, travelling platforms or robot tooling on linear axes. In these cases, it is no longer sufficient to consider only the movement of the person towards the hazard; the movement of the hazard towards the person must also be included in the safety distance.
For many press retrofits or stationary robot cells this will rarely be a game-changer. For AGV areas, shuttles, lifting systems and similar applications, the clear distinction between “static” and “dynamic” evaluation is useful.
4.3 Approach direction clearly separated
The 2024 edition draws a much sharper line between:
- orthogonal approach (person moves more or less straight towards the safeguard), and
- parallel approach (person moves along a safeguard or past a scanner field).
The angular limits and the associated formulas are better described and illustrated with additional examples. The mathematical approach is not fundamentally new, but the methodology is noticeably cleaner.
4.4 Single-actuated controls, two-hand controls and foot switches
There is more substance in the revised clauses on:
- two-hand controls,
- single-actuated control devices (e.g. a single start button),
- and foot-actuated controls.
The new edition provides clear minimum distances as a function of reaction time – including higher distances for foot controls compared to hand-operated buttons – and clearer rules for when a control device can be regarded as preventing access and when it cannot.
For presses with a foot pedal or single-hand control this is a welcome clarification: discussions with assessors and authorities will be easier to substantiate.
4.5 Interlocking guards and defeat
The requirements for interlocking guards (doors, covers) have been expanded:
- There is more emphasis on the fact that doors can be partly opened before the safety function is triggered.
- Flexible actuation elements (e.g. cables, rods) and their effect on the effective opening gap are addressed more explicitly.
Together with the parallel revision of EN ISO 14119:2025, this creates a more consistent picture of how to deal with defeat possibilities and how to dimension and position interlock devices.
4.6 New annexes and more complex allowances
Several new annexes provide:
- an overview of the physical quantities and symbols used,
- additional calculation examples,
- and extended guidance for scanner fields and more complex protection zones.
Specialist articles also point out that the allowances added to the calculated distance have become more differentiated – for example where posture, uncertainty and potential defeat have to be taken into account.
5. And what about the warning notice?
For the German edition, DIN has published an explicit warning notice referring to the 2025-10 issue. It states that one formula and one table heading in the original publication were incorrect and must be replaced by corrected versions.
In practice this means: if you work with the new DIN edition, you should always read it together with the warning notice and use the corrected formula/table – in particular where protection fields are arranged parallel to the direction of approach.
6. Practical consequences: what should manufacturers and retrofit planners do?
For new projects in Europe, EN ISO 13855:2024 is the latest edition; in Germany this is reflected by DIN EN ISO 13855:2025-10 as the current national standard. The old DIN EN ISO 13855:2010-10 has been withdrawn and is formally only relevant as long as it is still listed as a harmonised standard in the Official Journal.
For existing machinery and retrofits:
- Where calculations were properly done according to the 2010 edition, there is usually no dramatic need to redesign safety distances – but:
- dynamic applications,
- scanner-protected areas,
- and complex access situations
can benefit from the clearer structure of the new edition.
- For projects involving two-hand controls, foot pedals or single-hand controls, it is worth looking at the new minimum distances.
- Interlocking guards and enabling devices inside the safeguarded space should, in future, be evaluated based on the combined logic of ISO 13855:2024 and EN ISO 14119:2025.
My conclusion
The new EN ISO 13855 is not a revolution, but a substantial refinement:
- For many “classic” applications the numbers stay similar,
- for dynamic hazards, scanner-based protection, SRMCD and foot controls it brings more clarity – and more documentation work.
For an English-speaking audience this is exactly the message: you are familiar with the new edition, you see its limits, but you systematically apply the relevant new elements in your risk assessments and retrofit projects
Note on the source version
For my day-to-day work I currently use the German edition DIN EN ISO 13855:2025-10. This is the authorised German translation of EN ISO 13855:2024, so the technical content is identical to the English version. The explanations in this article are based on that German text.