Risk Assessment
What is QRA? Quantitative Risk Assessment Explained
Vinit Pandey · Published 18 November 2025 · Updated 28 June 2026
In short: QRA (Quantitative Risk Assessment) is a numerical methodology that combines failure frequency data with fire, explosion and dispersion consequence modelling to calculate individual risk and societal risk for a facility.
- Select Scenarios
- Failure Frequency
- Consequence Modelling
- Hazard Footprints
- Risk Integration
- Risk Contours / F-N Curve
Key takeaways
- Combines failure frequency data with fire, explosion, and dispersion consequence modelling
- Used where regulatory, land-use planning, or insurer requirements demand numerical risk
- Produces individual risk contours and societal risk as an F-N curve
- Results are typically benchmarked against ALARP tolerability criteria
QRA is the most rigorous level of process risk assessment, used where regulatory, land-use planning, or insurer requirements demand numerical risk figures rather than qualitative rankings.
The process begins with selecting representative loss-of-containment scenarios across a facility's hazardous inventory, then assigning failure frequencies using recognised industry databases and fault tree techniques.
Each scenario's physical consequences — toxic dispersion, jet fire, pool fire, flash fire, vapour cloud explosion — are then modelled using validated software to determine hazard footprint distances.
Frequency and consequence results are integrated across all scenarios and weather conditions to produce individual risk contours overlaid on the site plan, and societal risk expressed as an F-N curve.