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Effect of Recessed Sprinkler Installation on Sprinkler Activation Time and Prediction



Daniel M. Madrzykowski


The objectives of this study were to analyze the effects of recessed sprinkler installation on sprinkler activation time and evaluate the ability of sprinkler activation models to predict activation time. Full scale compartment fire tests were used to obtain activation times for four different types of sprinklers. The tests were conducted in an 18.9 m by 9.1 m by 2.35 m high compartment using floor based fires with constant heat release rates of 115, 155, 215, 290 and 520 kW. Non-dimensional sprinkler radial positions, r/H, of 0.64 and 1.28 were evaluated. In addition to sprinkler activation times, ceiling jet temperature, velocity and radiation measurements were made. Comparisons of activation times were made between sprinklers in a fully exposed pendent position versus those in a 25 mm recessed position. The 95% confidence limits for the test data were developed and a thermal tenability analysis was made to determine if the difference in response times was significant with respect to life safety. This analysis suggests that recessed installation does not have an adverse effect on life safety for the conditions tested. Several sprinkler activation models were compared to the test data. A modified sprinkler activation algorithm was developed that includes hot gas layer effects to the ceiling jet once the ceiling jet is fully developed.


sprinklers, sprinkler response, building technology, compartment fires, computer models, fire protection engineering, gas burners, large scale fire tests, sprinkler activation


Madrzykowski, D. (1993), Effect of Recessed Sprinkler Installation on Sprinkler Activation Time and Prediction, Thesis, [online], (Accessed June 16, 2024)


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Created January 1, 1993, Updated February 19, 2017