#QRA

Tunnel fire scene inside a long alpine road tunnel at night — wet asphalt reflects warm sodium lighting under a curved concrete vault, two jet fans hang from the ceiling, a green emergency exit sign glows above a steel refuge door and an emergency telephone on the right wall, a stopped lorry far down the bore trails grey smoke that flattens along the ceiling, and a tunnel safety engineer in a hi-vis jacket and white hard hat stands by a service pickup in the foreground reading an event-tree diagram and a falling risk curve on a tablet

📈 Fire Risk Assessment September 8, 2026 · 18 min read

Road Tunnel Fire Risk: The QRA Born From Mont Blanc 1999

The Mont Blanc tunnel fire killed 39 people in 1999. Here come the event trees, design fires, critical velocity and F-N lines that now govern tunnel QRA.

Modern fire-safety engineer's office at golden hour with a wall-mounted F-N curve chart — red intolerable zone above a downward-sloping diagonal, amber ALARP carpet in the middle, green broadly acceptable zone below, dotted plant curve descending through the carpet — and an engineer's hand pointing at the chart with a red marker

📈 Fire Risk Assessment May 8, 2026 · 19 min read

F-N Curve and Societal Risk: Drawing the Line on Safety

An F-N curve maps the societal risk a regulator will tolerate. Here is the math, the slope, the ALARP carpet, and where each sector draws the line.

Bow-tie risk diagram for fire — blue fault tree of causes converging into a central flame, and an orange event tree branching outward into five outcomes

📈 Fire Risk Assessment April 18, 2026 · 15 min read

Event Tree vs Fault Tree: Two Ways to Count Fire Risk

A fault tree asks how a fire happens; an event tree asks what happens next. The logic, the algebra, and a worked warehouse example.