Longevity effects on the performance of fire detectors

Abstract

Smoke detectors, a critical part of any fire detection system, are employed as safety devices to warn building inhabitants of life threatening particles resulting from combustion. Two types of detectors are currently on the market: ionization and photoelectric. How longevity effects the performance of smoke detectors is a growing concern, not only for industry, but the American citizen as well. To determine longevity effects on the performance of detectors, a testing chamber was designed and constructed to measure the percent obscuration/ft, of smoke particles at the point of detector activation. Three different tests were conducted: smoldering tests using Douglas fir wood and urethane foam as a fuel source, and a flaming fire test using newspaper as the fuel source. A total of three hundred eighty tests were conducted using new, five (5), ten (10), and fifteen (15) year old ionization and photoelectric smoke detectors in an uncleaned and cleaned condition. Comparisons between the detectors performance was analyzed and reviewed. The results indicate that smoke detectors are often unreliable and are inconsistent in their pattern of activating within an acceptable operating range of 0.5% - 4.0% obscuration/ft. This study indicates that fifteen (15) year old detectors generally activate at a percentage exceeding 4.0% obscuration/ft., or often do not activate. Because of this finding and the fact that homeowners tend to not replace detectors once they are installed, further investigation into the causes for this shortcoming is warranted. Additionally, because of the generally unreliable behavior of current detectors, further research into the development of detectors that are durable and reliable is also warranted.