Certification Expectations for Systematic Failure Avoidance in ISO 13849-1:2023

06 Nov 2026

Annex G is Informative... So, What Else Can Be Used?

One common misunderstanding encountered during ISO 13849-1:2023 assessments is the belief that Annex G can simply be ignored because it is informative. While this is technically correct, it misses a critical point: compliance with Clause 6.1.7 still needs to be demonstrated.

Annex G provides one recognised approach for demonstrating measures against systematic failures. If a manufacturer chooses not to use Annex G, they must still provide objective evidence showing that systematic failures have been adequately identified, prevented, controlled, and verified.

From a certification perspective, the question is not whether Annex G was followed. The question is:

"What evidence demonstrates compliance with Clause 6.1.7?"

If an alternative approach is used, it should provide an equivalent level of confidence that systematic faults capable of defeating the safety function have been prevented.

What Does Clause 6.1.7 Require?

Clause 6.1.7 requires systematic failures to be considered and controlled during the development of safety-related parts of control systems (SRP/CS). Unlike random hardware failures, which are addressed through architecture, MTTFd, DCavg, and CCF measures, systematic failures arise from errors in:

• Requirements specification
• Design
• Implementation
• Integration
• Verification
• Validation
• Configuration management
• Change management
• Maintenance processes

Systematic failures cannot be quantified using reliability calculations. Instead, confidence is achieved through robust engineering processes and supporting evidence. Unlike random failures, systematic failures propagate through the full design process. For example, an incorrect requirement in the SRS leads to incorrect design, which leads to incorrect testing procedures, therefore the ‘validated’ SRP/CS is not suitable for reducing the risk of the original hazard.

Why Annex G Exists

Annex G was included to provide examples of accepted techniques and measures for systematic failure avoidance.

It addresses topics such as:

Safety lifecycle activities Documentation practices Design reviews Verification activities

Validation activities Software development measures Fault avoidance techniques

For many manufacturers, Annex G effectively acts as a checklist of expected good engineering practice. This is therefore also a line of questioning that certification engineers will typically pursue in the absence of alternative evidence demonstrating compliance with Clause 6.1.7.

Although informative, certification bodies frequently use Annex G as a benchmark because it provides practical examples of how Clause 6.1.7 may be satisfied. If Annex G is not used, an assessor will typically expect equivalent evidence demonstrating the same objectives have been achieved.

Acceptable Alternative Approaches to Annex G

A manufacturer may demonstrate compliance through:

IEC 61508-Based Development	Many machinery products are developed using IEC 61508 methodologies. Evidence can often be mapped to the expectations of ISO 13849-1.
IEC 62061 Development Process	Where machinery safety systems are developed using IEC 62061 processes, much of the required systematic capability evidence may already exist.
Certified Safety Components	Where safety-related subsystems are already certified to standards such as: IEC 61508 IEC 62061 ISO 13849-1 IEC 60730 Annex H UL 1998 UL991 A significant portion of the systematic failure evaluation may already have been completed at component level. However, integration activities and application-specific development still require assessment.
Organisational Quality Processes	Some manufacturers rely on mature development processes incorporating: ISO 9001 design controls Formal design reviews Software quality procedures Change control systems Verification plans Validation testing While helpful, quality management systems alone are rarely sufficient unless they specifically address safety-related development.

Recommended Documentation Package

For a smooth ISO 13849-1:2023 assessment, manufacturers should ideally have the following documentation available:

Item	Example Evidence
Functional Safety Plan	Functional safety plan, Project development plan, Safety lifecycle definition
Requirements	Hazard/risk assessment, Safety requirements specification, Safety function definitions, Traceability matrix
Design	System architecture, Hardware architecture, Software architecture, Interface specifications
Verification	Design review records, Verification plan, Verification reports, Peer review records
Validation	Validation plan, Validation procedures, Validation reports, Fault testing records
Software	Software development plan, Coding standards, Source code review records, Static analysis reports, Unit and integration test reports
Configuration Management	Configuration management procedure, Version history, Release records, Build records
Change Management	Change control procedure, Engineering change records, Impact assessments
Competency	Training records, Competency assessments, Organisational responsibilities
Supporting Evidence	FMEA/FMEDA (where applicable), Reliability calculations, CCF assessment, MTTFd calculations, Supplier assessments, Third-party certifications

Conclusion

The key takeaway is that Annex G is informative, but Clause 6.1.7 is normative.

A manufacturer is not required to follow Annex G verbatim. However, they must provide objective evidence that systematic failures have been considered and addressed through a controlled development process. In practice, Annex G often becomes the benchmark against which alternative approaches are judged.

For certification assessments, the most successful projects are those that can clearly demonstrate:

1. Functional Safety Management Planning
2. Defined safety requirements.
3. Controlled design processes.
4. Independent verification activities.
5. Comprehensive validation.
6. Robust configuration and change management.
7. Competent personnel.
8. Appropriate software lifecycle controls.

If those elements can be demonstrated through documented evidence, compliance with Clause 6.1.7 can be justified even without explicit use of Annex G.