Last edit: 11/08/2023
After hazard identification, risk estimation shall be carried out for each hazardous situation.
The risk associated with a particular hazardous situation depends on the severity of harm and the probability of occurrence of that harm. The probability of occurrence of the harm is a function of:
- Exposure of persons to the hazard;
- Occurrence of a hazardous event;
- The possibility to avoid or limit the harm.
The purpose of risk estimation is to assess the severity of the dangerous situation, providing a value to be attributed to the risk. In the risk evalutation phase it will be determined whether the risk should be reduced.
Severity of harm
The severity of the damage can be estimated according to the following aspects.
Harm can be:
The extent of the harm must also be considered:
- One person;
- Several persons.
When carrying out a risk assessment, the maximum foreseeable severity must be taken into account, even if the probability of such an event is not high.
Probability of occurrence of harm
As already explained, the probability of harm occurring is related to the exposure of persons to the hazard, the occurrence of a hazardous event and the avoidability of harm.
The exposure of people to the hazard takes into account the frequency with which people access the hazardous area, the time spent in the hazardous area, the amount of people accessing the hazardous area and the reasons for doing so (maintenance, normal operation, troubleshooting, etc.).
The occurrence of a hazardous event is based on statistical and historical data of accidents and injuries. It can be either of technical or human origin.
The possibility of limiting or avoiding an injury depends on several factors such as: the qualification of the persons exposed to the hazard and their experience or knowledge of the machinery, the speed at which the hazardous situation can cause an injury (the slower it is, the greater the possibility of avoiding the injury), and awareness of the risk (through alarms, direct observation, etc.).
Risk Estimation Tools
There are a number of different tools for estimating risk, one of them being hybrid tools. This type of method combines two different approaches to risk estimation: the Risk Matrix approach and the numerical approach.
The method involves risk estimation based on the assignment of a numerical value to describe:
- Severity of Harm;
- Probability of occurrence of harm;
Assigned numerical values, a matrix is used to derive the Risk Estimate.
Below is an example of a Risk Matrix.