IRPA

Definition

IRPA, or Individual Risk Per Annum, reflects the risk of dying at a specified location when considering occupancy (presence factor) and potential protection factors (such as being inside a building or wearing protective clothing). It is a risk criterion that can be applied to occupied buildings or specific employee roles with a defined presence at different locations on a site.

Unlike the general Individual Risk (IR) definition, which assumes 100% presence in an unprotected outdoor scenario, IRPA takes into account actual occupancy and protection factors, providing a more accurate measure for assessing risk in real-world scenarios where individuals are not constantly present and may be indoors or protected.

Calculation

To calculate IRPA, a similar type of calculation is performed for Individual risk (LSIR). However, in this case, the buildings and corresponding occupancy are considered. The calculation of IRPA is performed as follows:

Application

• International QRA compliance: In real-world scenarios, assuming 100% presence and no protection might be extremely conservative. For instance, the Singapore QRA guidelines require risk assessments for onsite “occupied buildings” , while the Australian QRA guidelines assess onsite risk for workers corrected for presence at various site locations.

• Workplace safety: IRPA is essential for assessing workplace safety by considering the actual time employees spend in different areas. This helps in identifying high-risk roles and locations, enabling targeted safety measures and improvements.

• Regulatory compliance: Compliance with occupational safety regulations often requires demonstrating that the risk to employees is within acceptable limits. IRPA calculations provide the necessary data to meet these regulatory requirements.

• Emergency planning: Understanding the IRPA for different roles and locations aids in creating effective emergency response plans. It helps in prioritizing areas for evacuation and ensuring that emergency resources are allocated appropriately.

• Risk communication: IRPA data can be used to communicate risk effectively to employees and other stakeholders. It provides a clear understanding of risk levels associated with specific roles and locations, fostering a culture of safety and awareness.

IRPA in RISKCURVES

RISKCURVES allows defining a building, its protection and occupancy as well as different roles counting for different employees present in these buildings. In addition, the building itself may be occupied by a specified number of people, leading to an additional Potential Loss of Life (PLL) criterion:

RISKCURVES provides aggregated results for IRPA as a report for all buildings and roles, along with detailed results per building and role.

IRPA - building

Displays a risk grid within the zone and a detailed report depicting average IRPA, Potential Loss of Life, ​and risk ranking by dominating scenarios, highlighting which scenarios contribute to specific parts of the building.

IRPA - role

Includes total IRPA for the defined role including correction for presence and potential protection by buildings, and ranks risk by dominating locations, highlighting which buildings contribute for which part to this role.

For more information about how to calculate Individual Risk Per Annum in RISKCURVES, please refer to the article “Calculating IRPA in RISKCURVES”.