IEC 61508: Functional safety (generic, cross-industry)
IEC 61508 is the foundational international standard for achieving functional safety of electrical/electronic/programmable electronic (E/E/PE) safety‑related systems. It defines a risk‑based safety lifecycle, Safety Integrity Levels (SIL 1–4), and requirements spanning management, system/hardware, and software to reduce risks to an acceptable level.
It serves as the generic base for many sector standards (e.g., road vehicles, medical devices, process industry) and is often applied when no dedicated domain standard exists.
Scope and core concepts (at a glance)
- Risk‑based approach with target risk reduction expressed via SIL 1–4.
- End‑to‑end safety lifecycle from concept, hazard and risk analysis, allocation, development, integration, operation, maintenance to decommissioning.
- Requirements for management of functional safety, competence, independence, verification & validation, configuration and change management.
- Hardware topics: architectural constraints, diagnostic coverage, Safe Failure Fraction (SFF), Hardware Fault Tolerance (HFT), systematic capability.
- Software topics: software safety lifecycle, techniques/measures by SIL, verification, validation, tool qualification, proven‑in‑use.
Qualities addressed by IEC 61508
IEC 61508 is primarily focused on functional safety, but to achieve this, it addresses a number of other important quality attributes:
| Quality | Rationale |
|---|---|
| Safety | The core of the standard. It’s all about ensuring that systems operate safely and fail in a predictable and safe manner. |
| Reliability | Closely linked to safety. The standard requires high levels of reliability to ensure that safety functions are available when needed. |
| Maintainability | The standard’s emphasis on a structured lifecycle, traceability, and change control directly supports the ability to maintain the system over time. |
| Testability | A rigorous verification and validation process is a cornerstone of the standard. This includes requirements for reviews, static analysis, and testing, making the system easier to verify and test. |
| Fault Tolerance | The standard explicitly addresses fault tolerance through concepts like Hardware Fault Tolerance (HFT) and Safe Failure Fraction (SFF). |
Parts overview (very brief)
- Part 1: General requirements
- Part 2: Requirements for E/E/PE safety‑related systems (hardware/system)
- Part 3: Software requirements
- Part 4: Definitions and abbreviations
- Part 5: Examples of methods for the determination of safety integrity levels
- Part 6: Guidelines on the application of Parts 2 and 3
- Part 7: Overview of techniques and measures
Related standards
- ISO 26262 - Road vehicles — Functional safety — automotive derivative.
- IEC 62304 - Medical device software — software lifecycle for medical devices; often complemented by ISO 14971.
- IEC 61511 — Process industry sector derivative (SIS for process plants).
- IEC 62061 — Machinery sector derivative (functional safety of machinery control systems).
- IEC 62443 — Industrial automation and control systems security; complementary from a cybersecurity angle.