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Standards · Functional safety

IEC 61508 Edition 3: when it is due and what changes

Published 12 October 2026 · Updated 14 October 2026 · Source: IEC

Push-buttons and indicator lamps on an industrial control panel
Photo: Pexels

What happened

IEC 61508, the international standard for the functional safety of electrical, electronic and programmable electronic (E/E/PE) safety-related systems, is published as Edition 2, dated 2010. Work on Edition 3 is well advanced.

When is IEC 61508 Edition 3 due? January 2027 is IEC's current forecast. On 14 October 2026, IEC's project database listed all seven parts of Edition 3 (Parts 1 to 7) at the final draft (FDIS) stage, each with a forecast publication date of January 2027. The FDIS of Part 1 (65A/1267/FDIS) was circulated on 2 October 2026, with the voting report expected in November 2026.

Other dates in circulation are older. The IEC Webstore page for IEC 61508-1 still shows a forecast of 22 October 2026 (read 14 October 2026). The 61508 Association, a nominating organisation for the BSI committee that provides the UK's input to IEC subcommittee SC 65A, expects Edition 3 in early 2027.

What changes in Edition 3? The CDV of Part 1 (IEC document 65A/1164/CDV) was issued in Germany as the draft national standard E DIN EN IEC 61508-1 (VDE 0803-1):2025-12 on 28 November 2025, with comments closing on 28 January 2026. The publisher's listing, in German, summarises the draft's changes from the current edition:

  • it is updated to the 2024 ISO/IEC Directives, which brings many editorial changes, renumbered clauses and reworded notes;
  • the scope clarifies the position of artificial intelligence (as a class of software technology), human factors and IT security, and the related requirements are limited to the hazard and risk analysis (clauses 7.1.2.3 and 7.4.2.3 of the draft) and to references to external guidance;
  • the interfaces with the other parts of IEC 61508 are clarified, and requirements duplicated in other parts are removed;
  • the distinction between the required safety integrity level (SIL) and the achieved systematic capability (SC) is clarified;
  • more detailed requirements on the competence of people are provided (listed in IEC's abstract of the FDIS, not in the VDE summary of the earlier draft);
  • requirements on degrees of independence for the activities that ensure functional safety are introduced, in Annex B;
  • minor editorial errors are corrected, and the normative references and bibliography are updated.

These changes come from a draft, so the published Edition 3 may differ.

Why it matters

Part 1 sets the general requirements of the standard, and Parts 1 to 4 are basic safety publications, intended for use by IEC technical committees when they prepare their own standards (IEC 61508-1:2010, 1.4).

Two of the listed changes touch ideas that appear in everyday compliance work. Systematic capability is defined in Edition 2 as a measure, on a scale of SC 1 to SC 4, of the confidence that the systematic safety integrity of an element meets the requirements of the specified SIL (IEC 61508-4:2010, 3.5.9). Independence is already required for functional safety assessment: Edition 2 sets minimum levels of independence for the people carrying it out, graded by consequence in Table 4 and by SIL in Table 5 (IEC 61508-1:2010, 8.2.17 and 8.2.18).

Those two changes are the ones worth preparing for, because they change how compliance arguments are written. Suppliers and integrators who state systematic capability for their elements should expect to re-read those statements against the clarified relationship between SC and SIL. Anyone who runs functional safety assessments should compare their independence arrangements with the new Annex B once the published text is available.

Security is not new to Part 1: clause 7.4.2.3 of Edition 2 already says a security threats analysis should be carried out where the hazard analysis finds malevolent or unauthorised action reasonably foreseeable.

What it means for projects in progress. Projects running now are carried out against Edition 2, the edition in force, and that does not change until IEC lists the new edition as published. IEC's January 2027 forecast depends on the FDIS votes passing, so it is a date to watch rather than one to plan around.

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