Glossary · Risk assessment and risk reduction
Residual risk
German: Restrisiko
In machine safety, residual risk is the risk remaining after risk reduction measures have been implemented. The manufacturer must inform users about residual risks that are relevant to them.
- Machine safety
- Risk assessment
- Technical documentation
In one sentence
Residual risk is what remains after protective measures; it must be evaluated, accepted with a rationale and communicated in the information for use.
Example
A robot cell with a perimeter guard still carries a residual crushing risk during teach mode, which the manual addresses with reduced speed, an enabling device and specific training.
Explained in context
Context cards connect this term with others to answer one question. Also in British English and German.
- Attention and warning placement: from selective attention and habituation to where warnings goTransitional topicWhat does research on attention and warnings say about where and how warnings should be placed in instructions?UKDeutsch
- Documenting foreseeable misuse without making it an optionHow do instructions describe reasonably foreseeable misuse without presenting it as a way to use the product?UKDeutsch
- Operating modes in technical documentationWhy do operating modes change what the documentation of a machine has to say?UKDeutsch
- Where a warning belongs: safety chapter or before the taskShould a warning go into the safety chapter or directly before the step it concerns?UKDeutsch
How it applies
- Risk assessment: After each iteration of risk reduction, estimate the residual risk again and evaluate whether it is acceptable. If not, return to the three-step method.
- Technical documentation: Residual risks that users must manage go into the information for use, typically as a residual risk statement in the safety chapter and as warnings in the relevant tasks.
- Evidence: Link each residual risk to its hazard, the measures applied, the acceptance decision and the instructions that communicate it. Residual risk evidence makes this chain auditable.
- Maintenance: Residual risk can grow over time through wear, bypassed guards or modifications. Periodic inspection keeps the assumptions valid.
Residual risk vs. acceptable risk
Residual risk is a fact about what remains. Acceptable risk is a judgment against criteria. Informing users about a residual risk does not make an unacceptable risk acceptable.