Risk Matrix Calculations – Severity, Probability, and Risk Assessment

Risk Matrix Calculations – Severity, Probability, and Risk Assessment
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Safety Professionals use a risk matrix to assess the various risks of hazards (and incidents), often during a job hazard analysis. Understanding the components of a risk matrix will allow you and your organization to manage risk effectively and reduce workplace illnesses and injuries. Check out the three components of the risk matrix; severity, probability, and risk assessment that we utilize in Vector EHS Management software below.

No time to read? You can download our Risk Matrix Calculation Guide to review it at your convenience:

1. Severity

Severity is the amount of damage or harm a hazard could create and it is often ranked on a four point scale as follows:

  • Catastrophic - 4: Operating conditions are such that human error, environment, design deficiencies, element, subsystem or component failure, or procedural deficiencies may commonly cause death or major system loss, thereby requiring immediate cessation of the unsafe activity or operation.
  • Critical - 3: Operating conditions are such that human error, environment, design deficiencies, element, subsystem or component failure, or procedural deficiencies may commonly cause severe injury or illness or major system damage thereby requiring immediate corrective action.
  •  Marginal - 2: Operating conditions may commonly cause minor injury or illness or minor systems damage such that human error, environment, design deficiencies, subsystem or component failure, or procedural deficiencies can be counteracted or controlled without severe injury, illness, or major system damage.
  •  Negligible - 1 Operating conditions are such that personnel error, environment, design deficiencies, subsystem or component failure, or procedural deficiencies will result in no, or less than minor, illness, injury, or system damage.

2. Probability

Probability is the likelihood of the hazard occurring and it is often ranked on a five point scale:

  • Frequent - 5: Likely to occur often in the life of an item
  • Probable - 4: Will occur several times in the life of an item
  • Occasional - 3: Likely to occur sometime in the life of an item.
  • Remote - 2: Unlikely but possible to occur in the life of an item.
  • Improbable - 1: So unlikely, it can be assumed an occurrence may not be experienced.

Risk matrices come in many shapes and sizes. For more information on how to build a risk matrix that's right for your project, see our more detailed guide.

3. How to Use the Risk Assessment

The Risk Assessment values are determined by multiplying the scores for the Probability and Severity values together. The higher the risk assessment, the greater the overall risk for the project. This method helps balance the weight of severity and probability, as you can see in the following chart that displays the default risk assessment values:

5x4 risk matrix

Setting Control Measures for Risk Mitigation

After you’ve evaluated the risks of a project, you can prioritize which risk controls to implement first.

All risk mitigation activities should be clearly defined; objective, not subjective; and have specific, measurable outcomes.

Hazard identification and risk management should be processes of continuous improvement. Your organization’s risks may change over time, so you should periodically review and update your risk matrix.

Risk management tools can save health and safety professionals valuable time and resources.

Check out our hazards product information page to learn more about how the Vector EHS Management software can assist you in tracking, reporting, and analyzing your risks.

Hazard Analysis Software

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