Hazard Risk Rating

Posted: Feb. 4, 2020 • By Kevin Kohler

Hazard Risk Rating

What is a Hazard Risk Rating and how is it used?

Establishing a safe workplace means making sure that the hazards that workers might be exposed to are identified, assessed, and eliminated or controlled. Risk factors are evaluated in a formal process to obtain an overall risk rating for the hazard, task or task step being evaluated. This helps prioritize the hazards at our work sites.

We know the hazards we’re facing

Knowing that the hazards exist and ensuring that they have been properly documented and controlled, and workers trained, are two different matters.  Consider the following court case concerning the death of a tunnel foreman, reported by the Edmonton Journal on August 14, 2019:

…. a drainage tunnel (was)…. being constructed with a tunnel-boring machine.

This machine involved the use of a conveyor needing to be adjusted when it became misaligned, which was a “frequent occurrence,”….

“Workers were not provided formal training on how to adjust or align the conveyor,” (and) “workers (were) unaware of the potential hazards associated with their practice.”….

(The foreman) was instructed to fix an issue with the conveyor …. Being assisted by two labourers who didn’t have training in relation to hoisting or rigging, (the foreman) was standing on a walkway when the conveyor suddenly released toward the tunnel wall and pinned his head against the wall. 

No formal hazard training was provided, and workers relied on observing, or speaking to others who performed the task. 

How do we target the hazards that present the greatest risk?

This is the very reason for performing risk assessments on the hazards that we have identified. 

A risk assessment evaluates the risk posed to a worker by the hazard as it is currently encountered. The risk analysis might typically consider:

P – the probability that the hazard could cause harm

S – the severity of an injury or incident that the hazard could cause

E – the amount of exposure that workers have to the hazard

Standards are established to rank these risk factors.  For instance, P could range from 1 to 4, with one being a very low probability and 4 being very likely to occur. A consistent and workplace appropriate system should be used for establishing and ranking risk factors.

The Hazard Risk Rating (R) is a product, of the P, S and E risk ratings and can be expressed as:

R = (P) x (S) x (E)

Over selected ranges of possible values, the Hazard Risk Rating R can be expressed as low, medium or high (for example).  These values can be arrived at numerically or on a matrix with colour regions to indicate the areas of higher and lower risk factors.  It may be convenient to express P and E together if it’s difficult to untangle the two.  What’s important is that a consistent evaluation method is used that is appropriate to your workplace. 

You would initially target the higher risk hazards to determine which controls should be used according to the hierarchy of controls, with elimination or engineering controls preferred.  Training and retraining of workers can focus on those tasks with higher hazard risk ratings.

Best Practices

Hazard and risk assessments can be performed:

  • For the expected tasks in each individual job position
  • For a new or changed task before it exposes workers to uncontrolled hazards
  • Prior to beginning work at a new and unfamiliar worksite with un-assessed hazards
  • Prior to beginning work where conditions and tasks change daily or more often.

Documenting the hazard and risk assessments provides a basis for review, training and continuous improvement, to help ensure that workers are protected from the hazards that they may face.


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