#SFPE hydraulic model

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Evacuation test in a shopping mall atrium seen from a mezzanine — a thin grey smoke layer hangs flat under the glass roof while the air below stays clear, shoppers walk toward a green-lit exit and bunch up at the doors, red strobe beacons flash on the concrete columns, and a fire engineer in a navy jacket in the foreground holds a tablet showing two coloured bars labelled ASET and RSET

Fire Safety Engineering

ASET vs RSET: The Inequality Behind Every Evacuation Plan

ASET vs RSET decides whether a building passes. Here come the timeline, the tenability limits, the equations, and the one term that swings the answer most.

September 4, 2026 · 19 min read