Study on the Smoke and CO Alarm Concentrations to Develop a Smoke & CO Combination Detector

Abstract

In this study, we studied smoke and CO alarm concentrations to develop a combination detector for both smoke and CO. The derivation of smoke and CO alarm concentrations involved examining CO concentrations by smoke concentration using a sensitivity tester, typically employed for the type approval of photoelectric smoke detectors. Fire alarm and false alarm tests were performed to analyze smoke and CO concentrations further. In the fire alarm test conducted with polyurethane foam, generating black smoke with a reduced light scattering effect in the smoke chamber, no fire alarm was triggered, although the fire alarm concentration of the existing photoelectric smoke detector of sensitivity type 2 was set at 15 %/m. The measured smoke concentration reached only up to 10.2 %/m. Conversely, in the false alarm test with sliced pork belly and mackerel, false alarms occurred as the smoke concentration exceeded 15 %/m. The determined smoke and CO alarm concentrations for the combination detectors were established at 7.5 %/m for smoke (continuously for 10 s) and 15 ppm for CO (continuously for 10 s). Applying these concentrations in subsequent tests revealed an improved performance. In the polyurethane foam fire, where the existing smoke detector failed to operate, a fire alarm was issued at 328 s with the newly derived concentrations. For smoldering wood, the combination detector issued a fire alarm 305 s faster than the existing smoke detector. Furthermore, in the false alarm test with hamburger patty, sliced pork belly, and mackerel, the adaptability of false alarms was enhanced.