| Equation | Explanation |
|---|---|
| Risk = Likelihood × Severity | This is the most basic and widely used equation in risk assessment, where risk is calculated by combining the likelihood of occurrence with the severity of the consequences. |
| Residual Risk = Initial Risk − Controls | Residual risk refers to the remaining risk after implementing control measures. This helps assess the effectiveness of risk reduction strategies. |
| Risk Priority Number (RPN) = Severity × Occurrence × Detection | Used in Failure Modes and Effects Analysis (FMEA), the RPN helps prioritize risks by combining severity, likelihood (occurrence), and the likelihood of detecting the issue before it occurs. |
| Exposure = Duration × Frequency × Intensity | In exposure assessment, the risk of exposure to hazards (like chemicals, noise, or radiation) is calculated by considering how long, how often, and at what intensity workers are exposed to the hazard. |
| Incident Rate = (Number of Incidents × 200,000) / Total Work Hours | A common safety metric that calculates the frequency of incidents relative to the number of hours worked, using 200,000 as a base representing 100 employees working full time for one year. |
| Probability of Failure = Number of Failures / Total Opportunities | Used in reliability analysis, this equation calculates the likelihood of a system or component failing within a certain number of operational cycles or opportunities for failure. |
| Return on Investment (ROI) for Safety Measures = (Savings from Reduced Incidents − Cost of Controls) / Cost of Controls | This equation evaluates the financial return of implementing safety controls, helping organizations assess the economic benefits of investing in safety. |
| Severity Index (SI) = (Total Severity Points × 1,000) / Total Incidents | This index measures the average severity of incidents over time, allowing organizations to track trends and improvement. Higher values indicate more severe incidents. |
Table of Contents
Explanation of Key Equations:
- Residual Risk: After implementing controls, some risk still remains. The equation Residual Risk = Initial Risk − Controls helps evaluate whether the risk is reduced to an acceptable level.
- Risk Priority Number (RPN): The RPN is a critical tool in FMEA, combining severity, occurrence, and detection to prioritize which risks need immediate attention. It’s calculated as RPN = Severity × Occurrence × Detection.
- Incident Rate: This formula helps track how often safety incidents occur per hour worked. By multiplying by 200,000, you normalize the data for comparison across organizations or industries.
- Exposure: This formula helps determine worker exposure to hazards by factoring in the duration, frequency, and intensity of the exposure, ensuring that control measures target the most hazardous situations.
- Return on Investment (ROI): Evaluating the ROI for safety measures helps organizations justify investments in safety programs. It calculates how much financial benefit is derived from reducing incidents, making it easier to communicate the value of safety initiatives to decision-makers.
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