Glossary · Risk assessment and risk reduction
Acceptable risk
Also known as: tolerable risk
In machine safety, acceptable risk is risk that has been reduced to a level accepted under the applicable criteria and context. Whether a risk is acceptable depends on legal requirements, the state of the art and the documented acceptance criteria, not on a single universal threshold.
- Machine safety
- Risk assessment
In one sentence
Acceptable risk is the level a residual risk must reach under stated criteria; defining those criteria is part of the risk assessment, not an afterthought.
Example
For a palletizing robot, the team defines that crushing risks must meet the required Performance Level and be covered by perimeter guarding before the residual risk is accepted and recorded.
How it applies
- Risk assessment: Risk evaluation compares estimated risk against acceptance criteria. Write the criteria down before estimating, so they cannot be adjusted to fit the result.
- Machine safety: ISO 12100 speaks of adequate risk reduction, taking the state of the art into account. IEC 61508 uses the term tolerable risk for risk accepted in a given context based on current values of society.
- Evidence: Each accepted risk needs a risk acceptance justification with the criteria, assumptions, approvals and evidence.
- Technical documentation: Remaining risks that users must know about go into the information for use; acceptance by the manufacturer does not remove the duty to inform.
Acceptable risk vs. residual risk
Residual risk is whatever risk remains after measures are applied. Acceptable risk is a judgment that this remaining risk meets the criteria. Residual risk can exist without being acceptable, in which case further risk reduction is needed.