Citation

Martin G, Boehmer H, Olenick SM. Fire Technol. 2020; 56(2): 673-692.

Copyright

(Copyright © 2020, Holtzbrinck Springer Nature Publishing Group)

DOI

10.1007/s10694-019-00898-6

PMID

unavailable

Abstract

Smoke alarms are relied upon to notify building occupants of a fire, and the performance of these devices in the fire environment is critical for the safe evacuation of the building occupants. Development of smoke detection technology has focused primarily on the activation time of the smoke alarm and the amount of escape time they will provide. The growth rate of fires in industrial and residential settings has increased significantly in the past four decades, often attributed to the construction and materials of modern-day furnishings and contents compared to that in the 1970s. This changes the thermal environment smoke alarms are exposed to and raises the question whether they are able to alert the occupants before failing due to heat exposure. Research by Ashley et al. in 2005 showed that approximately 30 s of sounding time is necessary to reliably awaken a sleeping occupant and initiate egress. As research has primarily focused on the activation of smoke alarms, there is a gap in the industry knowledge of the thermally induced failure in these devices. Experiments using two different smoke alarm designs were performed in a heated tunnel with induced airflow. The alarms were heated until they reached a code-mandated audibility failure criterion of less than 5 dB above ambient levels, as well as complete cessation of the audible alarm sound during experimental testing. For these samples, reduction in sound signal started to occur at a component temperature of 56°C, and all alarms had stopped sounding when heated to 144°C. The results of a plunge heating test were used to compute a generalized two-stage Response Time Index for the thermal response of each type of smoke alarm. The output data from the NIST Home Smoke Alarm Tests performed in 2008 were used to calculate the estimated time when the smoke alarm would have thermally failed during those tests. The calculations showed that in the scenarios analyzed, both smoke alarm designs tested would provide more than the 30 s required, before reduced audibility or failure occurs. The failure of both alarm designs in just over 3 min shows that more research is needed applying this methodology to a wider range of alarm models and fire scenarios to ensure that smoke alarms are able to provide adequate protection in modern fires.

Language: en