Getting back to the discrepancies between Dual sensor #1 and Dual sensor #2.
Interestingly NIST, in an abstract, also noted that manufacturers have the freedom to set sensors separately and noted that they could not find any real benefit to standalone models.
(c) Copyright July 09
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Presented at the Fire Protection Research Foundation's 13th annual Suppression and Detection Research & Applications Symposium (SUPDET 2009), February 24-27, 2009, Orlando, FL
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Performance of Dual Photoelectric/Ionization
(combination) Smoke Alarms in Full-Scale Fire Tests
Thomas Cleary , Building and Fire Research Laboratory National Institute of
Standards and Technology Gaithersburg, MD, USA +1 301 975 6858 thomas.cleary@nist.gov
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The UL Standard 217, “Single and Multiple Station Smoke Alarms” allows for dual sensor alarms so long as the each sensor is primarily a smoke sensor and the design meets the Standard [6]. The alarm logic is an {OR}-type such that the the alarm is activated if either the photoelectric sensor or ionization sensor alarm threshold is met.
The individual sensor sensitivities are not tested separately. Therefore, manufacturers have the freedom to set each sensor’s sensitivity separately. Since an individual sensor can be set to meet all current sensitivity standards, it is not obvious what overall benefit is achieved from a dual alarm with an additional sensor technology that could be more or less sensitive than what would be found in a standalone unit employing such a sensor.
Additionally, another potential benefit of a dual sensor alarm may be realized by adjusting each sensor’s alarm threshold to reduce nuisance alarms. Thus, the sensitivity of each sensor factors into the overall performance of a dual alarm.
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Abstract:
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