Methods to Calculate the Response Time of Heat and Smoke Detectors Installed Below Large Unobstructed Ceilings.

Published

July 1, 1985

Author(s)

D D. Evans, D W. Stroup

Abstract

Recently developed methods to calculate the time required for ceiling mounted heat and smoke detectors to respond to growing fires are reviewed. A computer program, that calculated activation times for both fixed temperatures and rate of rise heat detectors in response to fires that increase in heat release rate proportionally with the square of time from ignition is given. This program produces equivalent results to the tables published in appendix C, Guide for Automatic Fire Detector Spacing, (NFPA 72E, 1984). A separate method and corresponding program are provided to calculate response time for fires having arbitrary heat release rate histories. This method is based on quasi-steady ceiling layer gas flow assumptions. Assuming a constant proportionality between smoke and heat release from burning materials, a method is described to calculate smoke detector response time modeling the smoke detector as a low temperature heat detector in either of the two response time models.

Citation

NIST Interagency/Internal Report (NISTIR) - 85-3167

Report Number

85-3167

NIST Pub Series

NIST Interagency/Internal Report (NISTIR)

Pub Type

NIST Pubs

Download Paper

https://doi.org/10.6028/NBS.IR.85-3167

Local Download

Keywords

ceilings, computer program, egress, escape, fire alarms, fire detection, fire suppression, heat detectors, smoke detectors, sprinkler systems

Citation

Evans, D. and Stroup, D. (1985), Methods to Calculate the Response Time of Heat and Smoke Detectors Installed Below Large Unobstructed Ceilings., NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NBS.IR.85-3167, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=100173 (Accessed October 27, 2025)