What is ISO 12100?
ISO 12100 is the international basic (type A) safety standard that sets out how a machinery manufacturer systematically identifies the hazards of a machine, estimates and evaluates the risks, and reduces those risks in a fixed order of priority to an acceptable level. Its goal is the safety of the people who build, operate and maintain the machine. The current edition is ISO 12100:2010, Safety of machinery – General principles for design – Risk assessment and risk reduction. In Europe it is harmonised as EN ISO 12100 (NEN-EN-ISO 12100 in the Netherlands) under the Machinery Directive, which makes it the starting point of almost every CE marking of a machine.
In an OT context, ISO 12100 is where safety functions are born: the risk assessment decides which risks a control system must handle, and standards such as ISO 13849-1 and IEC 62061 then decide how reliable that control system must be.
🧠 Where does ISO 12100 come from and what does it cover?
ISO 12100:2010 is a consolidation, without technical changes, of three older documents: ISO 12100-1:2003 (basic terminology and methodology), ISO 12100-2:2003 (technical principles) and ISO 14121-1:2007 (principles of risk assessment). Standards that referred to those older parts therefore did not need to be updated. The standard is maintained by ISO/TC 199 and, in parallel in Europe, by CEN/TC 114.
Its structure is straightforward:
- Clause 3 - terms such as hazard, hazardous situation, risk and residual risk
- Clause 4 - the strategy: risk assessment and risk reduction as an iterative process
- Clause 5 - the risk assessment itself
- Clause 6 - risk reduction in three steps
- Clause 7 - documentation of the assessment
- Annex B - examples of hazards, hazardous situations and hazardous events
For practical methods, such as risk matrices, risk graphs and scoring tables, the standard refers to the technical report ISO/TR 14121-2. ISO 12100 itself does not prescribe a single calculation method.
🧱 Where does ISO 12100 sit in the hierarchy of standards?
Machinery safety standards come in three levels. ISO 12100 sits at the top and applies to every machine.
| Type | Content | Examples |
|---|---|---|
| A (basic safety standard) | General principles for all machinery | ISO 12100 |
| B1 (generic aspects) | Safety aspects that recur across many machines | ISO 13849-1, IEC 62061, ISO 13855 (safety distances) |
| B2 (safeguards) | Specific protective devices | ISO 14119 (interlocking devices), NEN-EN-ISO 13850 (emergency stop), IEC 61496 (light curtains) |
| C (machine-specific) | Requirements for one type of machine | ISO 10218 (industrial robots), EN 415 (packaging machines) |
If a type C standard exists for your machine, it takes precedence. A risk assessment to ISO 12100 is still needed for hazards that the C standard does not cover.
🔧 How does a risk assessment to ISO 12100 work?
Clause 5 describes four steps. Together, the first three are called the risk analysis.
- Determine the limits of the machine - use limits (intended use and reasonably foreseeable misuse, operating modes, users), space limits, time limits (service life, maintenance intervals) and other limits such as environment and materials.
- Identify hazards - across the whole life cycle: transport, installation, commissioning, normal operation, fault finding, cleaning, maintenance and decommissioning.
- Estimate the risk - for each hazardous situation.
- Evaluate the risk - is risk reduction needed? If so, clause 6 follows and the assessment is repeated for the chosen measures.
When estimating risk, the standard combines two elements. The first is the severity of harm. The second is the probability that the harm occurs, which in turn depends on three factors:
| Element (§ 5.5.2) | Question | Example |
|---|---|---|
| Severity of harm | How serious is the injury, and how many people are affected? | Bruise, amputation, fatality |
| Exposure | How often and for how long is someone in the danger zone? | Once a week during changeover versus every cycle during manual loading |
| Occurrence of the hazardous event | How likely is the event? | Component reliability, experience with similar machines |
| Possibility to avoid or limit harm | Can the person recognise and avoid the hazard? | Speed of the movement, operator experience |
Note that the well-known parameters S, F and P do not come from ISO 12100 but from the risk graph in ISO 13849-1, which determines the required Performance Level (PLr). IEC 62061 uses its own matrix with four parameters to select a SIL. Both methods build on the risk assessment to ISO 12100.
🛡️ What is the three-step method for risk reduction?
Clause 6 sets a fixed order of priority. You only move to the next step when the previous one is not sufficient.
- Inherently safe design (§ 6.2) - eliminate or reduce the hazard in the design itself: lower forces and speeds, no sharp edges, enough clearance between moving parts, lower voltages.
- Safeguarding and complementary protective measures (§ 6.3) - guards, interlocks, light curtains and other protective devices, plus complementary measures such as the emergency stop and means of safely isolating energy. This is where the safety functions that a safety PLC or safety relay performs are created.
- Information for use (§ 6.4) - signs, warnings, the instruction manual and training for the residual risk. A warning sticker is therefore never the first measure.
An organisational measure taken by the user, such as Lock-out Tag-out or personal protective equipment, complements the manufacturer’s measures but does not replace them.
⚠️ Which hazards does ISO 12100 list?
Annex B provides a list that serves as a checklist. The main groups are:
| Hazard group | Example |
|---|---|
| Mechanical | Crushing, cutting or entanglement by moving parts or pressing mechanisms |
| Electrical | Contact with live parts in a control cabinet or motor |
| Thermal | Burns from hot surfaces or steam |
| Noise | Hearing damage from prolonged exposure |
| Vibration | Hand-arm vibration from hand-held tools |
| Radiation | Laser radiation or welding radiation |
| Materials and substances | Inhaling dust, fumes or aerosols |
| Ergonomic | Awkward posture during operation, manual tooling changes |
| Environment of use | Slippery floor, poor lighting |
| Combinations | Hot, moving parts in a dusty environment |
An unexpected start-up, for example due to a software fault in a PLC or a wrong command from the HMI, is not a separate hazard group in the standard. It is a hazardous event that releases a mechanical or electrical hazard, and that is exactly where ISO 12100 meets control engineering.
🔐 How does ISO 12100 deal with cybersecurity?
The 2010 edition does not mention cyber threats. That is a growing gap, because the Machinery Regulation (EU) 2023/1230, which replaces the Machinery Directive from 20 January 2027, requires protection against corruption of safety-related software and against malicious interference by third parties.
ISO/TC 199 is therefore working on a second edition. A draft from December 2024 was not approved, and a second draft failed its vote at the end of 2025. The third draft, ISO/DIS 12100.3, appeared on 1 August 2026, and voting on it closed on 15 September 2026. Among other things, it adds:
- Cyber threats and data corruption as a cause of hazardous situations, with a reference to ISO/TR 22100-4
- AI and machine learning, with a reference to ISO/TR 22100-5
- Remote access, indirect control and remote software updates as potential sources of new hazards
- Marking of the version of safety-related software and of the values of safety-related parameters
- A definition of tolerable risk and a new diagram of the iterative process
The European Commission requested harmonised standards for the Machinery Regulation in January 2025, with 20 January 2026 as the deadline. That deadline was missed, so EN ISO 12100:2010 remains the reference for now. Until the new edition is published, the most practical approach is to assess cyber risks separately with IEC 62443-3-2 and link the results to the safety risk assessment.
🏭 How do you apply ISO 12100 in practice?
A typical approach for a new machine or production line in the Netherlands or elsewhere in the EU:
- Assemble a team - mechanical designer, controls engineer, an experienced operator and the maintenance department; no single person sees every hazard.
- Define the limits - intended use, operating modes (automatic, manual, setup) and foreseeable misuse such as bypassing a door switch.
- Walk through the life cycle - use Annex B as a checklist for each phase and each danger zone.
- Estimate and evaluate - choose a method from ISO/TR 14121-2, for example a risk matrix, and document the reasoning.
- Reduce in order of priority - design, safeguarding, information; for each safety function determine the PLr to ISO 13849 or the SIL to IEC 62061.
- Iterate and document - reassess new measures and include the result in the technical file.
A robot cell with a cobot, the safety distances of ISO 13855 and the electrical equipment to IEC 60204-1 therefore all start from the same ISO 12100 assessment. Anyone who substantially modifies an existing machine is considered its manufacturer under the Machinery Regulation and has to repeat that assessment. In the Netherlands the employer is also bound by the Arbowet, which requires a separate risk inventory and evaluation of the workplace.
❓ Frequently asked questions
Is ISO 12100 mandatory?
ISO 12100 is not legally mandatory as a standard, but the Machinery Directive does require a risk assessment for every machine. Following EN ISO 12100 gives a presumption of conformity with that requirement. That is why almost all machinery manufacturers in Europe use ISO 12100 as the basis for CE marking.
What is the difference between ISO 12100 and ISO 13849-1?
ISO 12100 determines which risks a machine has and which measures are needed. ISO 13849-1 takes over for measures implemented through a control system and specifies how reliable that safety function must be, expressed as a Performance Level. ISO 12100 therefore always comes first.
Which risk estimation method does ISO 12100 prescribe?
ISO 12100 does not prescribe a single method, but it does define the elements: severity of harm and probability of harm, built from exposure, occurrence of the event and the possibility of avoidance. Practical methods such as risk matrices and risk graphs are described in ISO/TR 14121-2. Whatever method you choose must be applied consistently and traceably.
Is ISO 12100:2010 still valid?
Yes, ISO 12100:2010 and EN ISO 12100:2010 are the current editions, even though a revision is under way. The third draft of the new edition appeared in August 2026, with additions on cybersecurity and AI. Once ISO publishes the new edition, the old one is expected to be withdrawn immediately, while in the EU a transition period of around two and a half years is expected for the presumption of conformity.
Does ISO 12100 also apply to existing machines?
ISO 12100 is written for designers of new machinery, but its method is also used for retrofits and for assessing existing machines. A substantial modification requires a new risk assessment to ISO 12100. Employers also use the method to check older machines against the requirements for work equipment.
How are ISO 12100 and cybersecurity related?
ISO 12100:2010 does not address cybersecurity, whereas the Machinery Regulation requires protection against tampering with safety-related software from 2027. The new edition of ISO 12100 does include cyber threats and data corruption. Until it is published, you combine the ISO 12100 assessment with a cyber risk assessment to IEC 62443-3-2.
📌 In summary
ISO 12100 is the type A standard that every machinery manufacturer uses to define limits, find hazards, estimate and evaluate risks, and reduce them in the order design, safeguarding, information. All other machinery safety standards, from ISO 13849-1 to IEC 60204-1 and ISO 14119, build on that assessment. The ongoing revision brings cybersecurity and AI into the method, in line with the Machinery Regulation.
ISO 12100 is the starting point of all machinery safety: without a risk assessment to this standard there is no well-founded safety function and no CE marking.