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Algorithm to Describe the Spread of a Wall Fire Under a Ceiling



Henri E. Mitler


After some discussion of wall fires, the effects that a ceiling has on a wall fire are analyzed and discussed qualitatively. There are two kinds of effects: first, when the upper sill of the ventilating opening lies below the ceiling (as is usual), a layer of hot gas is trapped, which heats the walls by convection and radiation; the heated ceiling also radiates to the walls. A calculation which uses the wall-fire computer model SPREAD is carried out to demonstrate how these effects can be calculated now. Second, when the flame impinges on the ceiling, it bifurcates and spreads horizontally, rather than vertically. A simple algorithm is presented which calculates the spread rate of these horizontal flame extensions, as well as the modified pyrolysis rate, due to the modified radiation feedbacks.
NIST Interagency/Internal Report (NISTIR) - 5547
Report Number


algorithms, ceilings, ceiling fires, computer models, fire growth, fire spread, pyrolysis rate, wall fires


Mitler, H. (1994), Algorithm to Describe the Spread of a Wall Fire Under a Ceiling, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed April 12, 2024)
Created November 1, 1994, Updated November 10, 2018