Alpert Correlation
Definition
An expression derived by Ronald Alpert at FM Global for ceiling jet temperature and velocity as functions of heat release rate, ceiling height, and radial distance from the plume axis. Used to predict detector activation.
- Originator
- Ronald Alpert, FM Global
- Predicts
- Ceiling jet temperature and velocity
- Key inputs
- Heat release rate, ceiling height, radial distance
- Practical use
- Detector and sprinkler activation timing
Common questions
What is a ceiling jet in this context?+
It is the fast-moving, hot layer of gas that spreads radially outward beneath a ceiling once a rising fire plume strikes it, and it is what actually contacts and activates smoke or heat detectors before the room fills with smoke.
What are the practical limits of applying this correlation to a real fire scene?+
The correlation assumes a relatively unconfined, flat, unobstructed ceiling and a fire with a known or estimable heat release rate, so its predictions become less reliable in compartments with beams, sloped ceilings, or ventilation-limited fires whose heat release rate is hard to reconstruct after the fact.
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