Fire Technology

, Volume 54, Issue 5, pp 1265–1282 | Cite as

The Response Time of Different Sprinkler Glass Bulbs in a Residential Room Fire Scenario

  • Magnus ArvidsonEmail author


The response time of fire sprinklers is essential for their performance, especially in applications where life safety protection is desired. The earlier the sprinkler activates, the smaller the size of the fire. Most commercial residential sprinklers are fitted with 3 mm, 68°C glass bulbs. However, thinner sprinkler glass bulbs with lower operating temperatures are available. The aim of this study was to determine the response time—and the corresponding heat release rate—of different glass bulbs in a residential room fire scenario. A series of tests were conducted inside a compartment measuring 3.66 m by 3.66 m having a ceiling height of 2.5 m. The compartment was either enclosed or had two walls removed to provide a more ventilated scenario. A propane gas burner was positioned at one of the corners. The mass flow rate of the gas was controlled such that either ‘slow’, ‘medium’ or ‘fast’ fire growth rate scenarios were simulated. In each test, nine Response Time Index (RTI) and operating temperature combinations were tested. Each test was replicated three times. In addition, two commercial fire detectors were tested. The results show that the fire is considerably smaller upon activation with a combination of a low RTI and a low operating temperature, as compared to the 3 mm, 68°C glass bulb typically used for residential sprinklers. The operating temperature proved to have a larger impact on the results than the RTI. The heat from the fire was typically detected by the fire detectors prior to the activation of the sprinkler glass bulbs, especially for the ‘slow’ and ‘medium’ fire growth rate scenarios.


Sprinkler glass bulbs Response Time Index (RTI) Operating temperature Fire detectors Response time Residential room fire scenario 



Jürgen Teschner from Job GmbH provided the sprinkler glass bulbs and Jan Blomqvist from Siemens AB the fire detectors and associated equipment as well as provided help with the data recording. The technical input and support from these people is gratefully acknowledged. The staff at RISE is also gratefully acknowledged, especially Morgan Lehtinen who was responsible for the measurement equipment and Mikael Björnram that manufactured the glass bulb mounts. The tests were financed by the Swedish Civil Contingencies Agency (MSB) under the project “Analys av brandsäkerhetens fysiska bestämningsfaktorer och tekniska åtgärder som stöd till nollvisionen” (“Analysis of fire safety physical determinants and technical measures to decrease the number of casualties in residential fires”) which is gratefully acknowledged.


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Safety and Transport – Fire ResearchRISE Research Institutes of SwedenBoråsSweden

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