3.4 Hazard Assessment
Once hazards have been identified, it is necessary to prioritize which hazards will be controlled first. Much like hazard recognition, hazard assessment is not just a technical practice. Through prioritizing, certain hazards will be brought to the forefront, and will therefore be more likely to be controlled, while others will be downgraded and likely receive little or no attention. It is important to be mindful of who benefits and who is harmed by the prioritization decisions.
Risk assessment is a common tool used by those determining the priorities in hazard assessment. Risk is the likelihood that a hazard will result in injury or ill health. A risk assessment quantifies the likelihood of injury or ill health by assessing the probability, consequences, and exposure posed by the hazards:
- Probability is the likelihood that the hazard will result in an incident.
- Consequences refers to the severity of injury or ill health that will result from an incident.
- Exposure refers to how often or regularly workers come in contact with the hazard.
Figure 3.1 Simplified Risk Assessment Tool
Figure 3.1 gives an example of a simplified tool for assessing the probability, consequences, and exposure associated with a hazard. Assessors use the description (e.g., rare, possible, probable, or likely). Each descriptor is then assigned a numerical value (e.g., 1, 2, 3, or 4).
Probability: Likelihood hazard will result in an incident.
☐ ☐ ☐ ☐
Rare (1) Possible (2) Probable (3) Likely (4)
Consequences: Severity of injury/ill health caused by incident.
☐ ☐ ☐ ☐
Negligible (1) Marginal (2) Significant (3) Catastrophic (4)
Exposure: Frequency workers contact the hazard.
☐ ☐ ☐ ☐
Rare (1) Occasional (2) Frequent (3) Continuous (4)
Once the probability, consequences, and exposure of a hazard have been quantified, they can be inputted into a mathematical formula to quantify the risk:
| risk = probability × consequences × exposure |
The greater the final number, the greater the risk posed by the hazard. Quantifying risk allows us to compare the relative risk of several hazards. For example, workers in a gas station face all manner of hazards, including slippery surfaces, gasoline fumes, and the potential for robbery. Without looking at the assessment below, which of these three hazards should the employer control first? Most people tend to say robbery. Yet quantifying the risks suggests that robbery poses the least risk of the three hazards:
- Slippery surfaces: Possible (2) × Significant (3) × Frequent (3) = 18
- Exposure to gasoline fumes: Possible (2) × Significant (3) × Continuous (4) = 24
- Robbery of cash on premises: Rare (1) × Catastrophic (4) × Continuous (4) = 16
Risk assessment tools allow the assessor to compare hazards, either overall or on a factor-by-factor basis, in order to identify which hazards should have the highest priority for control. It may be important, for example, to note that robbery poses the least risk of the three hazards but has the highest level of consequence and is a hazard to which workers are continuously exposed. These features may influence the type of control that is appropriate.
Likelihood that a hazard will result in injury/ill health.
Quantifying the likelihood of injury/ill health by assessing the probability, consequences, and exposure posed by the hazards.
The likelihood that the hazard will result in an incident.
The severity of injury/ill health that will result from an incident.
How often or regularly workers come in contact with the hazard.
