61508ISO

ISO/IEC 61508 is an international standard that provides a generic framework for the functional safety of electrical, electronic, and programmable electronic safety-related systems (E/E/PE SRS). It establishes a risk-based approach to design, implement, operate, and maintain safety functions across diverse industries, and it serves as the basis for many sector-specific safety standards.

The standard covers the entire safety lifecycle, from concept through decommissioning. It emphasizes hazard analysis and risk assessment, the definition of safety requirements, system design and integration, verification and validation, configuration management, operation and maintenance, and the creation of safety cases. A key concept is the Safety Integrity Level (SIL), with four levels (SIL 1 to SIL 4) that express increasing requirements for reliability and risk reduction. Higher SILs demand more rigorous development processes, validation, and proven-in-use life-cycle data. Independence of safety-related activities and proper management of competence, documentation, and change control are also central.

ISO/IEC 61508 is published as a multi-part framework that includes general requirements, requirements for E/E/PE safety-related systems, and software requirements, with additional parts and sector-specific derivatives used to tailor the framework to particular industries. It is widely referenced by national standards and has influenced related standards such as ISO 13849-1 (safety of machinery), IEC 62061 (safety-related electrical control systems), and IEC 61511 (process safety).

In practice, organizations use ISO/IEC 61508 to guide the design and operation of safety functions, determine appropriate SIL targets, and prove through audits and evidence that safety objectives are achieved throughout the system life cycle.