How does a risk assessment to EN ISO 12100 work?
EN ISO 12100 describes an iterative process made up of risk analysis and risk evaluation. Risk analysis covers determining the limits, identifying hazards and estimating the risk; risk evaluation decides whether reduction is necessary. The risk follows from the severity of the harm and the probability of its occurrence, which in turn is made up of frequency of exposure, probability of the event and the possibility of avoidance.
How is the process of the standard structured?
EN ISO 12100 distinguishes two blocks that together make up the risk assessment.
Risk analysis consists of three parts: determining the limits of the machine, identifying the hazards and estimating the risk for each hazard.
Risk evaluation follows and answers a single question: is the risk adequately reduced? If the answer is no, measures are taken following the three-step method and the whole run starts again.
This cycle is the core of the standard. It ends only when all hazards are adequately reduced and the measures themselves have not created new, unevaluated hazards.
Which elements make up the risk?
| Element | Question | Typical grading |
|---|---|---|
| Severity of harm (S) | How severe is the possible injury? | Slight and reversible up to severe, irreversible or fatal |
| Frequency and duration of exposure (F) | How often and how long is somebody in the hazard zone? | Seldom up to frequent or continuous |
| Probability of occurrence (W) | How likely is the hazardous event to occur? | Very low up to high |
| Possibility of avoidance (V) | Can the person still avert the harm? | Possible under certain conditions down to scarcely possible |
The standard prescribes no fixed formula. The risk graph is a widely used aid, but it is a tool, not the standard itself. What matters is that the chosen method is documented traceably.
When does a risk count as adequately reduced?
Which hazards are overlooked most often?
- Hazards in secondary operating modes: setting, changeover, trial runs with the guard open.
- Maintenance and fault clearance, often under time pressure and with safeguards bypassed.
- Stored energy: springs, pressure accumulators, raised masses, capacitors.
- Ergonomic hazards such as awkward postures, obstructed view or controls that are hard to reach.
- Hazards from materials and emissions: dust, vapours, noise, radiation.
- Interactions with neighbouring machines and with the environment at the installation site.
- Foreseeable misuse, for instance deliberately bypassing a safeguard in order to work faster.
Sources and standards
- EN ISO 12100: safety of machinery, risk assessment and risk reduction
- EN ISO 13849-1: safety-related parts of control systems
- EN ISO 13857: safety distances to prevent hazard zones being reached
- Machinery Regulation (EU) 2023/1230, Annex III
Editions of standards and their harmonised status change continuously. Check standard numbers and editions against the current list in the Official Journal of the EU before applying them. This article is a technical classification and does not replace legal advice.
Frequently asked questions
Is EN ISO 12100 a harmonised standard?
EN ISO 12100 is the basic type-A standard for safety of machinery and the methodological basis of risk assessment. Check the current listing of harmonised standards in the Official Journal of the EU, as it is changing in the course of the Machinery Regulation.
What is the difference between type-A, type-B and type-C standards?
Type-A standards contain basic concepts and design principles for all machinery (EN ISO 12100). Type-B standards deal with individual safety aspects or safeguards (for example EN ISO 13849-1, EN ISO 13857). Type-C standards apply to a specific machine type and take precedence over type-A and type-B standards in case of conflict.
Do I have to use a risk graph?
No. The standard prescribes no particular evaluation method. What matters is that the method suits the machine, is applied consistently and is documented traceably.
Does EN ISO 12100 still apply under the Machinery Regulation from 2027?
The method remains the reference process for risk assessment. The Machinery Regulation presupposes a risk assessment without prescribing a procedure. Check the edition and the listing status before applying it.
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This article was produced with AI assistance and reviewed for technical accuracy before publication. Editorial responsibility within the meaning of Art. 50(4) of the AI Act (EU) 2024/1689 lies with Heinrich Knutas.
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