Demystifying Functional Safety Certification

29 Jan 2026

What IEC 61508 Certificates Really Mean – and What They Often Don’t

Functional Safety certification is often treated as a badge of assurance – a simple signal that a product is “IEC 61508 compliant” and therefore suitable for use in safety-related applications. In reality, the situation is far more nuanced, and misunderstanding what a certificate represents can introduce risk rather than reduce it.

IEC 61508:2010 does not mandate that products must be certified in order to claim compliance with the standard. Certification is optional. However, when used correctly, product certification can provide valuable independent evidence of a product’s integrity, availability, and reliability when implemented as part of a Safety Instrumented System (SIS).

The challenge lies in understanding what a Functional Safety certificate actually represents, how it was derived, and whether it truly supports the safety integrity claims being made.

The Problem: Certification Without Consistency

Unlike many product certification schemes, IEC 61508 does not operate under a single, globally harmonised conformity assessment framework for product certification. In practice, this lack of a harmonized conformity assessment framework leads to several challenges:

• There is no uniform methodology for issuing IEC 61508 certificates
• Certification Bodies may apply different interpretations of the standard
• The content, depth, and clarity of certificates and supporting reports can vary significantly

For manufacturers and system integrators, this creates a real risk. You may purchase a “certified” product without fully understanding what has actually been assessed, or whether the product can genuinely support the required Safety Integrity Level (SIL) in your application.

In some cases, ambiguous or incomplete certificates only reveal their weaknesses during bidding or project execution, leading to redesign, re-assessment, or even re-certification – all of which carry cost, delay, and reputational risk.

Certification Is Not the Same as Compliance

A Functional Safety certificate does not automatically mean a product is suitable for your safety function. Compliance is demonstrated through the ability of the product to perform a defined safety function to the required integrity, not simply through possession of a certificate.

To demonstrate compliance with IEC 61508:2010, a product assessment must show that the device meets the random hardware and systematic capability requirements for the intended SIL when performing a defined safety function, under stated assumptions and constraints.

In other words, certification must be:

• Function-specific
• SIL-specific
• Usage-specific

Anything less risks being misleading.

What Should a Functional Safety Certificate Contain?

To remove ambiguity and support meaningful use by end users and system integrators, best practice Functional Safety product certificates should include, as a minimum, the following information:

Core Integrity Parameters:

• Random Hardware Safety Integrity Capability (SIL)
• Systematic Safety Integrity Capability (SC)
• Route to compliance (1H, 2H, 1S, 2S, or 3S)
• Assessment standard and edition (e.g. IEC 61508:2010)

Product Classification:

• Product Type (Type A or Type B per IEC 61508-2, Clause 7.4.4.1.2/3)
• Hardware Fault Tolerance (HFT)
• Safe Failure Fraction (SFF)
• Diagnostic Coverage (DC)

Reliability Data:

• Failure rates (λsu, λsd, λdu, λdd)
• Probability of Dangerous Failure on Demand (PFDavg)
• Probability of Dangerous Failure per Hour (PFH)

Safety Function Definition:

• Clear definition of the safety function(s) assessed
• Demand mode (low demand / high demand / continuous)
• Proof test interval assumptions
• Assumptions and limitations

Without this information, a certificate may provide confidence without clarity, which is rarely sufficient in real-world SIS design, verification, or bidding scenarios.

Why This Matters for Manufacturers and Integrators

A Functional Safety certificate is only as strong as the technical evidence that underpins it. Where key parameters are missing, unclear, or poorly justified, there is a real risk that incorrect SIL claims are made at the system level, assumptions used during SIL verification are invalid, or challenges arise from EPCs, end users, or independent assessors reviewing the safety case. In many projects, these weaknesses only become visible late in the lifecycle, resulting in re-work, additional assessment effort, and avoidable cost and schedule impact. Conversely, a well-structured certificate that is supported by robust and transparent assessment reports enables faster system integration, clearer SIL allocation and verification, reduced overall project risk, and greater acceptance by end users, integrators, and authorities having jurisdiction.

Key Takeaways

1. Always request the supporting assessment reports used as the basis for certification, not just the certificate itself.
2. Understand the credentials of the certifying body: are they accredited, and to what scheme?
3. Where certification is issued by a non-accredited third party, perform due diligence to verify alignment with IEC 61508:2010 requirements.
4. Ensure both random hardware integrity and systematic capability have been explicitly assessed and stated.

Functional Safety certification can be a powerful tool – but only when its scope, assumptions, and limitations are properly understood. In Functional Safety, clarity is as important as compliance.

How Intertek Can Help

Intertek supports manufacturers, system integrators, and end users in navigating the complexity and ambiguity that can exist around Functional Safety assessment and certification activities. Rather than treating certification as a standalone outcome, Intertek focuses on ensuring that Functional Safety assessments are technically robust, transparent, and genuinely usable at the system level. This includes independent review and assessment of products against IEC 61508:2010, with clear definition of safety functions, demand modes, assumptions, and limitations, supported by traceable evidence and assessment reports.

Where products are already certified, Intertek can provide independent verification, gap analysis, or due diligence reviews to help confirm whether the information presented on existing certificates is sufficient and correctly aligned with IEC 61508 requirements for the intended application. For manufacturers seeking certification, Intertek can support the full assessment lifecycle, from functional safety management and lifecycle process reviews through to hardware reliability analysis, systematic capability assessment, and preparation of clear, defensible certification outputs.

By focusing on clarity, consistency, and technical credibility, Intertek helps ensure that Functional Safety certificates are not just issued, but can be confidently relied upon by EPCs, system integrators, end users, and authorities when making SIL-related decisions.