Ceiling Jet Temperature Calculator

Calculate ceiling jet temperature and velocity at any radial distance from fire centerline per Alpert correlations

Input Parameters

Results

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Ceiling Jet Temperature
C
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Temperature Rise
C
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Ceiling Jet Velocity
m/s
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Est. Detector Response Time
s
Note: Alpert correlations assume smooth, unobstructed flat ceiling with no draft curtains or beams. For beamed ceilings, temperatures may be higher and velocities lower. These correlations are the basis for detector spacing in NFPA 72.

Reference

Alpert Ceiling Jet Correlations: For r/H <= 0.18: dT = 16.9 * Q^(2/3) / H^(5/3) V = 0.96 * (Q/H)^(1/3) For r/H > 0.18: dT = 5.38 * (Q/r)^(2/3) / H V = 0.195 * Q^(1/3) * H^(1/2) / r^(5/6) Detector: t ~ RTI * ln(dT/(Tjet-Tact)) / sqrt(V)