ISO 13849-1 vs IEC 62061: Choosing the Right Functional Safety Standard for Your Machine
Document version: 1.0 | Fact-checked: August 2026 | Standards status verified against ISO, IEC, European Commission and certification-body sources.
Executive summary
- ISO 13849-1 (current edition ISO 13849-1:2023, EN ISO 13849-1:2023) rates the reliability of safety-related parts of control systems (SRP/CS) using Performance Levels (PL a–e). It is technology-neutral: electrical, electronic, hydraulic, pneumatic and mechanical control systems all qualify.
- IEC 62061 (current edition IEC 62061:2021, EN IEC 62061:2021, with amendments A1:2024 and A2:2026) rates safety-related control systems (SCS) using Safety Integrity Levels (SIL 1–3), the machinery-sector adaptation of the IEC 61508 approach.
- The two standards were deliberately aligned in their 2023/2021 editions: they now share identical PFHd targets, comparable architectures and harmonized software requirements, and cross-use of components designed to one standard is explicitly permitted.
- PL ↔ SIL correspondence (informative): PL b/c ≈ SIL CL 1, PL d ≈ SIL CL 2, PL e ≈ SIL CL 3. PL a has no SIL equivalent.
- Bottom line for machine builders: if your Type-C (product) standard or customer specification names one route, use it. Otherwise choose ISO 13849-1 for electro-mechanical / pneumatic / hydraulic safety circuits and IEC 62061 for programmable electronic systems with complex software. A single design can usually be documented under both.
1. What each standard is
| ISO 13849-1:2023 | IEC 62061:2021 | |
|---|---|---|
| Full title | Safety of machinery — Safety-related parts of control systems — Part 1: General principles for design | Safety of machinery — Functional safety of safety-related control systems |
| Issuing body | ISO (TC 199) / CEN (TC 114) | IEC (TC 44) / CENELEC |
| Rating scale | Performance Level PL a → e | Safety Integrity Level SIL 1 → 3 (SIL 4 is not used for machinery) |
| Scope | Safety-related parts of control systems (SRP/CS) in any technology | Safety-related control systems (SCS) in any technology (since 2021; previously electrical only) |
| Operating modes | High demand / continuous mode only | High demand / continuous mode only |
| Low-demand applications | Out of scope → use IEC 61508 series | Out of scope → use IEC 61508 series |
| Companion standard | ISO 13849-2 (validation); ISO 13849-1:2023 Annex N software | Based on IEC 61508; verification & validation built into the standard |
| EU harmonization | EN ISO 13849-1:2023, cited in the OJEU under the Machinery Directive (May 2024), transition until 15 May 2027 | EN IEC 62061:2021, cited in the OJEU under the Machinery Directive (April 2022, CID 2022/621) |
Historical note. The 2005 edition of IEC 62061 covered only electrical/electronic/programmable-electronic systems (SRECS); ISO 13849-1 traditionally covered everything else. The 2021 edition removed that technology boundary, which is why the two standards now overlap almost completely in scope. A merger project (ISO 17305) was abandoned, and the revision committees instead harmonized the two documents clause by clause.
2. The two rating systems: PL and SIL
Both standards ultimately quantify the same thing: the average frequency of a dangerous failure per hour (PFHd) that the safety function may exhibit. The PFHd target ranges are identical in both documents.
2.1 PL ↔ SIL ↔ PFHd correspondence table
| Performance Level (ISO 13849-1) | PFHd range (1/h) | Equivalent SIL (IEC 62061 / IEC 61508) |
|---|---|---|
| a | ≥ 10⁻⁵ to < 10⁻⁴ | — (no SIL equivalent) |
| b | ≥ 3×10⁻⁶ to < 10⁻⁵ | SIL CL 1 (upper portion) |
| c | ≥ 10⁻⁶ to < 3×10⁻⁶ | SIL CL 1 |
| d | ≥ 10⁻⁷ to < 10⁻⁶ | SIL CL 2 |
| e | ≥ 10⁻⁸ to < 10⁻⁷ | SIL CL 3 |
SIL ranges per IEC 61508: SIL 1 = ≥ 10⁻⁶ to < 10⁻⁵; SIL 2 = ≥ 10⁻⁷ to < 10⁻⁶; SIL 3 = ≥ 10⁻⁸ to < 10⁻⁷ (1/h). The PL–SIL correspondence is informative, not a substitution rule — a PL is a performance range, a SIL is an integrity claim limit. Never mix verification methods mid-project.
2.2 How each standard achieves the target
| Design element | ISO 13849-1:2023 | IEC 62061:2021 |
|---|---|---|
| Structural building block | Categories B, 1, 2, 3, 4 (behavioural architecture classes) | Subsystem architectures: basic, single channel with diagnostics, double channel |
| Quantitative inputs | Channel MTTFd (low 3–10 y / medium 10–30 y / high 30–100 y), Diagnostic Coverage DC (none <60% / low 60–90% / medium 90–99% / high ≥99%), CCF scoring (≥ 65/100 points) | PFHd per subsystem, DC-based architectural constraints (replaces the older SFF/HFT tables from the IEC 61508 heritage), CCF measures |
| Output label | Achieved performance level PL | Achieved SIL (the 2021 edition renamed "SIL claim limit / SIL CL" to "maximum SIL" of a subsystem) |
| Software requirements | Clause 7 (use cases: software safety requirements, parameterization, verification) | Clause 8 (use cases, independence of software verification) |
| Validation | ISO 13849-2-based validation (adopted as Clause 10 of the 2023 edition) | Validation within the standard; degrees of independence defined |
| Typical tooling | SISTEMA (IFA, free), PAScal, SafetyEvaluator | PAScal, SIL verification spreadsheets, supplier PFHd data |
Category ⇄ architecture correspondence (informative):
| ISO 13849-1 Category | Approx. IEC 62061:2021 architecture | Key behaviour |
|---|---|---|
| B | Basic | Single channel, no diagnostics, any component quality |
| 1 | Basic (well-tried components & principles) | Single channel, proven components |
| 2 | Single channel with diagnostics | Periodic test function detects faults |
| 3 | Double channel | Redundant channels, fault detection, DC low–medium |
| 4 | Double channel | Redundant channels, high DC, accumulation of faults considered |
3. Risk assessment: how the required level is determined
Both standards start from a risk assessment according to EN ISO 12100 (risk reduction process: risk analysis → risk evaluation → risk reduction). The difference is the parameter set used to derive the required level.
| Step | ISO 13849-1 | IEC 62061:2021 |
|---|---|---|
| Starting point | Risk assessment per EN ISO 12100 | Risk assessment per EN ISO 12100 |
| Parameters | Risk graph: S severity (S1 slight / S2 serious), F frequency & duration of exposure (F1 seldom / F2 frequent), P possibility of avoiding (P1 possible / P2 hardly possible) | Se severity of harm (1–4), Fr frequency & duration of exposure (1–5), Pr probability of occurrence of the hazardous event (1–5), Av possibility of avoiding/limiting harm (1–5) |
| Output | Required performance level PLr (a–e) | Required SIL (1–3) via the standard's assignment table |
| Style | Qualitative graph → quantitative verification | Semi-quantitative parameter classification + quantitative verification |
| Documentation emphasis | Safety requirements specification; risk graph result | Safety Requirements Specification (SRS) is mandatory (explicit clause) |
4. Strengths and limitations
| Aspect | ISO 13849-1 | IEC 62061 |
|---|---|---|
| Technology coverage | Excellent — genuinely covers pneumatic, hydraulic, mechanical and electrical | Good — all technologies since 2021, but the heritage and much of the data ecosystem is electrical/electronic |
| Learning curve | Shorter; PL logic and SISTEMA are widely taught | Steeper; SIL/SRS concepts assume IEC 61508 familiarity |
| Simple electro-mechanical circuits (safety relays, contactors) | Natural fit | Possible, but heavier than needed |
| Complex programmable systems (safety PLCs, safety drives, networks) | Possible (Cat 2/3/4 + software clauses) | Natural fit — designed for it |
| Cross-industry recognition | Very high (esp. Europe, machine tools, packaging, robotics) | Very high where IEC 61508 culture exists (drives, process, semiconductor) |
| Ecosystem | Component MTTFd/DC data ubiquitous; SISTEMA free tool | Supplier PFHd data for subsystems; PAScal and similar |
| Software depth | Use-case based (2023) | Use-case based, independence of verification required (2021) |
| Weakness | Software/systematic-integrity requirements less explicit than IEC 61508-style thinking | Historically over-engineered for simple circuits; documentation burden heavier |
5. Typical applications and industry preferences
| Application / industry | Common route | Why |
|---|---|---|
| Safety relays, contactor-based circuits, presses, guillotines | ISO 13849-1 | Electro-mechanical SRP/CS; Cat 1–4 concept fits perfectly |
| Packaging machinery, food & beverage lines | ISO 13849-1 (often specified by Type-C standards) | Simple-to-medium safety functions, PL c/d typical |
| Machine tools, machining centres | ISO 13849-1 (e.g., PL d / Cat 3 per many Type-C standards) | Prescriptive in C-type standards |
| Industrial robots & AGVs | ISO 13849-1 (e.g., PL d / Cat 3 referenced by ISO 10218-1:2011, ISO 3691-4) | Established precedent; new editions increasingly accept either route |
| Safety drives / adjustable speed drives (STO, SLS, SS1…) | IEC 62061 / IEC 61508 family | IEC 61800-5-2 publishes SIL-rated safety functions |
| Programmable safety controllers, safety networks (PROFIsafe, CIP Safety, FSoE) | IEC 62061 | SIL/PFHd data published per subsystem; software depth required |
| Safety light curtains / ESPE (EN/IEC 61496) | Both — datasheets claim Type 4 → PL e, Cat. 4, SIL 3 | Dual-rated product claims are the norm (see §7) |
| Semiconductor, pharmaceutical equipment | IEC 62061 | Engineering culture and customer specs |
Always check the applicable Type-C standard first: many product standards prescribe which functional-safety route to take (and at what level). When a Type-C standard is silent, either B-standard is acceptable.
6. Decision guidance and dual-compliance strategy
Which standard should you use?
Choose ISO 13849-1 when… - Your safety functions are implemented with relays, contactors, pneumatic/hydraulic valves or simple electronics. - A Type-C standard or customer specification references PL / Category. - Your team is new to functional safety — the PL route is the gentler entry point. - You want free tooling (SISTEMA) and abundant component MTTFd/DC data.
Choose IEC 62061 when… - The safety function is executed by programmable electronic systems (safety PLCs, drives, networks) with substantial software. - Your supply chain publishes SIL/PFHd data (drives, safety controllers). - Customers or integrators demand an IEC 61508-heritage approach, SRS documentation and verification independence. - You operate in sectors where SIL language is the norm.
Both standards, one design (dual compliance) — recommended practice: 1. Perform one risk assessment per EN ISO 12100; derive both PLr and SIL (the informative correspondence table makes this easy). 2. Write a Safety Requirements Specification (SRS) once — both standards now effectively require it. 3. Choose subsystems whose published data covers both worlds (most safety components are dual-rated). 4. Verify the PFHd budget once; it is the common currency. 5. Claim "PL e, Category 4, SIL CL 3" style dual ratings in datasheets and DoCs — this is exactly how the leading safety sensor suppliers present Type 4 products. 6. Validate per ISO 13849-2 requirements (now embedded in ISO 13849-1:2023 Clause 10) and the validation provisions of IEC 62061; keep one technical file for both.
7. What this means for safety light curtains (ESPE)
Electro-sensitive protective equipment (light curtains, light grids, area scanners) is designed to EN/IEC 61496 (Part 1 general, Part 2 AOPD, Part 3 AOPDDR) and rated for functional safety as follows:
| ESPE type (EN/IEC 61496) | Usable in applications up to |
|---|---|
| Type 2 | PL c (ISO 13849-1) / SIL 1 (IEC 62061) |
| Type 3 (introduced in the 2020 4th edition) | PL d / SIL 2 |
| Type 4 | PL e (Category 4) / SIL 3 |
Two practical takeaways for buyers: 1. "Type 4" is the top ESPE class — it corresponds to the highest PL/SIL ratings a machine can claim, suitable for hazards with serious injury potential (PL e / SIL 3). 2. Type examination matters. Because EN/IEC 61496 is not a harmonized standard under the EU Machinery Directive/Regulation, there is no automatic presumption of conformity — independent type examination by a recognized body (e.g., TÜV, DEKRA, SGS) is the established market practice. A DADISICK Type 4 safety sensor carries type-examination and dual PL e / SIL 3 claims so integrators can rely on the numbers without re-deriving them.
8. Version and harmonization status — keep this table current
| Standard | Edition | EN version | OJEU harmonization (Machinery Directive) | Notes |
|---|---|---|---|---|
| ISO 13849-1 | 4th ed., 2023-04 | EN ISO 13849-1:2023 (2023-11) | Cited May 2024; replaces EN ISO 13849-1:2015; transition until 15 May 2027 | 2023 edition restructured; new software, EMI-immunity and SRS annexes |
| ISO 13849-2 | Validation | Revision in progress (EN ISO 13849-2:20xx) | — | Expect a new edition aligned with ISO 13849-1:2023 |
| IEC 62061 | 2nd ed., 2021-03 | EN IEC 62061:2021 (2022-01) | Cited April 2022 (CID 2022/621); EN 62061:2005 presumption ended 11 Oct 2023 | Amendments: IEC 62061:2021/AMD1:2024 (EN A1:2024), AMD2:2026 (EN A2:2026) |
| EN ISO 12100 | 2010 | EN ISO 12100:2010 | Cited | Risk assessment & risk reduction (Type-A standard) |
Regulatory timeline to watch (EU): - Until 19 January 2027: Machinery Directive 2006/42/EC applies; Declaration of Conformity may reference both Directive and Regulation if compliant. - From 20 January 2027: Machinery Regulation (EU) 2023/1230 applies exclusively (no transition period). Harmonized standards for the Regulation are expected to carry over with minor adjustments — apply EN ISO 13849-1:2023 and EN IEC 62061:2021 now to be future-proof. - The Regulation adds: software/cyber-security requirements for safety functions, stricter conformity assessment for higher-risk machinery, new economic-operator duties (importers/distributors), and digital technical documentation.
9. References and sources
- ISO 13849-1:2023, Safety of machinery — Safety-related parts of control systems — Part 1: General principles for design (ISO; 4th edition, 2023).
- ISO 13849-2:2012, … Part 2: Validation (ISO).
- IEC 62061:2021 + AMD1:2024 + AMD2:2026, Safety of machinery — Functional safety of safety-related control systems (IEC; 2nd edition, 2021).
- IEC 61508 (all parts), Functional safety of electrical/electronic/programmable electronic safety-related systems (IEC).
- EN ISO 12100:2010, Safety of machinery — General principles for design — Risk assessment and risk reduction.
- EN/IEC 61496 series (Parts 1, 2, 3), Safety of machinery — Electro-sensitive protective equipment (IEC 61496-1:2020, 4th ed.).
- Regulation (EU) 2023/1230 on machinery, OJ L 165, 29 June 2023 (EUR-Lex) — applicable 20 January 2027.
- European Commission, Machinery sector page and harmonized standards database (single-market-economy.ec.europa.eu).
- ISO Online Browsing Platform (iso.org/obp) — edition/status verification.
- Pilz, EN/IEC 61496 and IEC 62061 technical reference pages (pilz.com) — PFHd/SIL tables and harmonization status.
- DGUV Test, EU Machinery Regulation conformity-assessment guidance (dguv.de).
Document control: verify standard editions and OJEU citation status at least annually or before publishing updates. Last verified: 2026-08.
