IEC 61508

IEC 61508 is an international standard that provides a framework for the functional safety of electrical, electronic, and programmable electronic (E/E/PE) safety‑related systems. It is considered the foundational or “umbrella” standard for functional safety across various industries.

Its purpose is to ensure that systems designed to perform safety functions will do so reliably and without introducing unnecessary risks. It achieves this by defining process requirements for the entire safety lifecycle, from the initial concept and risk assessment through design, implementation, operation, maintenance, and decommissioning of safety‑related systems.

The core concept of functional safety is compliance of the process with the requirements of the system. In other words, a safety‑critical function can be considered safe if it has been developed by following a safe process. Compliance is the precondition for safety. Compliance is like having a driving license: it does not guarantee safety, i.e., being a safe driver.

IEC 61508 is important for functional safety because it establishes a systematic and rigorous approach to managing risks associated with E/E/PE systems. In an increasingly automated world, many systems perform critical safety functions, such as preventing explosions, controlling machinery, or ensuring safe transportation. Failures in these systems can lead to severe consequences, including injury, environmental damage, or economic loss.

IEC 61508 provides a common set of principles and requirements to reduce these risks to an acceptable level, promoting consistency and confidence in safety‑critical applications across different sectors.

IEC 61508 serves as the master standard for functional safety, with numerous industry‑specific standards deriving their core principles from it.

For instance, in the automotive industry, ISO 26262 adapts the concepts of IEC 61508 to the unique automotive development lifecycle and its associated hazards. Similarly, for railway applications, EN 50716 translates IEC 61508’s requirements into the railway domain. In process industries, IEC 61511 applies its principles, and for machinery, IEC 62061 is relevant. Even in aerospace, standards such as DO‑178C (for airborne software) reflect its underlying safety philosophies.

While each of these sector‑specific standards tailors the requirements to its domain, they all trace their lineage back to the comprehensive framework established by IEC 61508, ensuring a unified approach to managing functional safety across diverse applications.

IEC 61508 is a generic, reusable functional safety standard for electrical, electronic, and programmable systems. Organizations that already have a domain‑specific safety standard (e.g., ISO 26262 for automotive, EN 50128 for railway, IEC 61511 for the process industry) typically follow that standard instead. Only organizations without a sector‑specific standard must comply directly with IEC 61508. Because most safety standards are derived from it, IEC 61508 serves as a cross‑domain reference for ensuring Safety Integrity Levels (SILs), safety lifecycle management, and proper tool and library qualification.

The system, the hardware, and the software are the key parts responsible for safety. Their requirements are typically considered within the compliance argumentation. However, the real risks often lie in the safety requirements for software tools and libraries. These are sometimes overlooked, but if an assessment reveals that they were not considered, it can take a long time to close this gap. Software tools are not part of the product, but they can heavily impact product safety, for example by inserting an error into the product or by failing to detect one. Therefore, the risks of all software tools must be considered as part of safety planning. Critical tools must be qualified.

Software libraries are pieces of software not written by the project team but are pre‑existing components, such as open‑source libraries for mathematical functions. Compilers sometimes silently add libraries into the product, and developers often prefer to reuse existing software. This is good practice and generally safe, since the risk of undetected errors in widely used libraries is typically lower because many developers rely on them. For this reason, IEC 61508 allows libraries to be qualified with a subset of requirements specified in the so‑called Route 3s.

The compliance risk is that these libraries can easily be overlooked. But if an assessor asks for a memory map of the product with all software units and functions, then there must not be a single unqualified function in the safety‑relevant parts. This does not mean that an entire library has to be qualified—only the functions that are actually used in the product. It is sufficient to qualify only the used library functions. A detailed library analysis can help reduce the qualification effort and save costs.

By combining deep functional safety expertise with a strong focus on tools and libraries, Validas helps organizations turn IEC 61508 requirements into actionable, scalable processes. This not only strengthens safety compliance but also accelerates development timelines and builds lasting confidence in safety‑critical systems.