Glossary · Risk estimation methods
Exposure (risk estimation)
In machine safety risk estimation, exposure is the frequency and duration with which people are exposed to a hazard. It is one of the elements that determine the probability of harm.
- Machine safety
- Risk assessment
In one sentence
Exposure in risk estimation rates how often and how long people are near a hazard, based on tasks such as operation, setting, cleaning and maintenance.
Example
An operator loads parts into a press every 30 seconds, which is frequent exposure, while a technician enters the drive enclosure only during annual maintenance.
How it applies
- Risk estimation: ISO 12100 lists factors such as the need for access to the hazard zone, the nature of access, time spent in the zone, the number of persons and the frequency of access.
- Functional safety: The ISO 13849-1 risk graph uses parameter F: seldom to less often and/or short exposure (F1) versus frequent to continuous and/or long exposure (F2). IEC 62061 has a corresponding frequency and duration parameter.
- Human factors: Estimate exposure for all tasks, not only production. Troubleshooting and cleaning often involve closer and less protected access than normal operation. A job hazard analysis at the user's site shows real patterns.
- Evidence: Exposure assumptions should match the likelihood used elsewhere and be updated when throughput or maintenance practice changes.
Exposure vs. hazardous situation
A hazardous situation is the circumstance of being exposed. Exposure, in risk estimation, rates how often and how long that circumstance occurs.