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Results from a Full-scale Smoke Alarm Sensitivity Study



Thomas G. Cleary


A series of 24 full-scale experiments was conducted during the summer of 2008 to examine the effects of alarm type (photoelectric, ionization, and dual sensor), alarm location, fabric type (100 % cotton and 100 % polyester), polyurethane foam density, ignition scenario, and room configuration, on smoke alarm performance. A two-level, fractional factorial design of eight experimental configurations was developed around the five factors: fabric type, foam density, fire location, ventilation, and ignition scenario. A structure, designed to represent a single-story home or apartment, was constructed inside the Large Fire Laboratory at NIST for the experiments. The fire source was a chair mockup consisting of a seat and back cushion of a specific cover fabric and foam density, weighing approximately 6 kg, and resting on a metal frame that was subject to a small propane gas flame, or an electric cartridge heater to initiate smoldering. Each experimental configuration was conducted three times. Smoldering fires were allowed to progress until they naturally transitioned to flaming fires except for one test that was terminated early due to time constraints. The smoldering to flaming transition times ranged from 81 to 182 minutes. Each fire progressed for a time sufficient to produce multiple hazards (smoke, heat, and toxic gases). All alarms tested were purchased from retail outlets and activated at their preset levels. Photoelectric, ionization, and dual photoelectric/ionization alarms were co-located at multiple locations to facilitate comparisons of each alarm type, and different designs of the same type of alarm. It was observed that the composition and ignition mode of the chair mock ups can significantly affect smoke alarm response, as can the fire room volume and airflow. A photoelectric alarm did not always outperform an ionization alarm in smoldering fires. One dual alarm model yielded the shortest or nearly shortest average alarm time for all experimental configurations, while another dual alarm model yielded mixed results.
Proceedings Title
Suppression and Detection Research and Applications Symposium, February 24-27, 2009 (SUPDET 2009)
Conference Dates
February 25-27, 2009
Conference Location
Orlando, FL


smoke alarms, fire tests, smoldering


Cleary, T. (2009), Results from a Full-scale Smoke Alarm Sensitivity Study, Suppression and Detection Research and Applications Symposium, February 24-27, 2009 (SUPDET 2009), Orlando, FL, [online], (Accessed May 22, 2024)


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Created February 27, 2009, Updated February 19, 2017