Performance of Dual Photoelectric/Ionization Smoke Alarms in Full-Scale Fire Tests.
Performance of Dual Photoelectric/Ionization Smoke
Alarms in Full-Scale Fire Tests.
Cleary, T. G.
Suppression and Detection Research Application: A
Technical Working Conference, 13th Annual. SUPDET 2009.
Proceedings. Fire Protection Research Foundation.
Feburary 24-27, 2009, Orlando, FL, 2009.
photoelectric detectors; ionization detectors; smoke
detectors; large scale fire tests; UL 217; smoldering;
living rooms; bedrooms; time; data analysis; statistics;
Data from two full-scale residential smoke alarm fire
test series were 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 alarm responses 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 faster than ionization alarms and 79 s faster 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 thresholds could be defined by the
sensor outputs. In that test series, dual alarms, with
individual sensor sensitivities equal to their
counterpart alarm sensitivities, activated 261 s faster
on average than ionization alarms (with sensitivity
settings of 4.3 %/m smoke obscuration for the ionization
sensors) and 35 s faster 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 reach the alarm
threshold, the dual alarm activated 67 s faster on
average than the photoelectric alarm. While in cases
were a photoelectric sensor was the first to reach the
alarm threshold, the dual alarm activated 523 s faster
on average than the ionization alarm. Over a range of
ionization sensor settings examined, dual alarm response
was insensitive to the ionization sensor setting for
initially smoldering fires and fires with the bedroom
door closed, while dual alarm response to the kitchen
fires was very sensitive to the ionization sensor
setting. Tests conducted in the National Institute of
Standards and Technology (NIST) fire emulator/detector
evaluator showed that the ionization sensors in
off-the-shelf ionization alarms and dual alarms span 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 smoke sensitivity
may be a goal.