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Performance of Dual Photoelectric/Ionization Smoke Alarms in Full-scale Fire Tests

Published

Author(s)

Thomas G. Cleary

Abstract

Data from two full-scale residential smoke alarm fire test series was analyzed to estimate the performance of dual sensor photoelectric/ionization alarms as compared to co-located individual photoelectric and ionization alarms. Dual alarms and aggregated photoelectric and ionization alarms were used to estimate dual alarm performance. It was observed that dual alarms with equivalent or higher sensitivity settings performed better than individual photoelectric or ionization alarms over a range of flaming and smoldering fire scenarios. In one test series dual alarms activated 539 s earlier than ionization alarms, and 79 s earlier than photoelectric alarms on average. In another test series, individual alarm sensor outputs were calibrated against a reference smoke source in terms of light obscuration over a path length (percent smoke obscuration per unit length.) so that alarm threshold could be defined by the sensor output. In that test series dual alarms activated 261 s earlier on average than ionization alarms (with sensitivity settings of 4.3 %/m smoke obscuration for the ionization sensors) and 35 s earlier on average than the photoelectric alarms (with sensitivity settings of 6.6 %/m, for the photoelectric sensors.) In cases where an ionization sensor was the first to respond, the dual alarm activated 67 s sooner on average than the photoelectric alarm. Tests conducted in the fire emulator/detector evaluator showed that the ionization sensors in ionization alarms and dual alarms cover a range of sensitivity settings. While there appears to be no consensus on sensitivity setting for ionization sensors, it may be desirable to tailor sensor sensitivities in dual alarms for specific applications, such as near kitchens where reducing nuisance alarms may be a goal, or in bedrooms where higher fire sensitivity may be a goal.
Proceedings Title
Research Foundation's 13th annual Suppression and Detection Research and Applications Symposium, February 24-27, 2009 (SUPDET 2009)
Conference Dates
February 25-27, 2009
Conference Location
Orlando, FL

Keywords

smoke alarms, fire detection, fire tests

Citation

Cleary, T. (2009), Performance of Dual Photoelectric/Ionization Smoke Alarms in Full-scale Fire Tests, Research Foundation's 13th annual Suppression and Detection Research and Applications Symposium, February 24-27, 2009 (SUPDET 2009) , Orlando, FL, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=901648 (Accessed April 14, 2024)
Created February 27, 2009, Updated February 19, 2017