Calculating Individual Risk

About Individual Risk

Individual Risk (IR) is defined as the probability per year that a person at a specific location, who is continually and unprotected present at that spot, becomes a victim of an accident involving hazardous substances. In some countries, this is referred to as "Locational Risk (LSIR)" indicating that the value is specific to one location or coordinate. The criteria for Individual Risk assume a 100% presence and an unprotected situation outdoors.

Calculating Individual Risk

RISKCURVES automatically calculates the Individual Risk for each scenario. To perform the risk calculation, you need to define the consequence model inputs and the base frequencies for each event. The results of the Individual Risk calculation are presented in three formats: Iso Risk Contours, FX curve, and Iso Risk grid.

Iso Risk contours

• Description: Iso Risk contours illustrate locations on a map where the Individual Risk has identical values for a set of different levels.

• Usage: Iso Risk contours can be displayed at various levels of the RISKCURVES project tree, including calculation sets, cumulation sets, comparison sets, and individual equipment.

FX curve

• Description: The FX curve shows the Individual Risk as a frequency plotted against the distance from the release point, for different wind directions.

• Usage: This curve helps in understanding how the risk changes with distance and directional wind directions.

Iso Risk grid

• Description: The Iso Risk Grid allows you to read Individual Risk values at any location in the map using the crosshair tool. By default, the grid uses a cell size of 10 meters although this can be changed in Calculation settings.

• Usage: Activate the Risk Grid in the legend to view and analyse risk values at specific coordinates. This is particularly useful for detailed risk assessments at precise locations.

Note

The risk grid is only visible when Expert mode is selected.

Note

For scenarios involving very large affected areas (e.g., routes spanning many kilometres or toxic events impacting vast regions), the grid might become excessively large (> 10^6 cells). In such cases, a re-sampling process is performed automatically by RISKCURVES to manage memory usage efficiently.

Conclusion

Individual Risk calculations in RISKCURVES offer a comprehensive tool for assessing and managing risk associated with hazardous substances. Iso Risk contours, FX curves, and Iso Risk grids provide detailed insights into risk distribution, enabling informed decision-making in safety management, regulatory compliance, facility siting, emergency response planning, and public communication. These tools are essential for minimising risk and ensuring the safety and well-being of communities and facilities.