Abstract: Photoelectric smoke fire detector is the mainstream used in the civil aircraft cargo, is the key to guarantee the safe operation of the aircraft. The detector is based on the smoke particles of light scattering signal for alarm, but because of suspended particles in the air (water vapor or dust, etc.) also has scattering effect, will trigger the fire detector alarm occurs. False alarms caused by such defects in principle occur from time to time. Taking the cargo plane typical combustion corrugated sheets, ju wood and the cotton rope as examples, blue light scattering power (representation for the surface area of concentration), infrared light scattering power (characterization for volume concentration) and particulate matter sauter mean diameter of fire characteristic parameters were analyzed, to optimize the fire characteristic parameters for the development of composite detectors. The results showed that: under atmospheric pressure, blue and infrared light have a good response to the change of particle concentration, and the sault average particle size can distinguish fire smoke particles from non-fire smoke particles, which can reduce the false alarm rate effectively.

Key words: photoelectric smoke detector, fire characteristic parameters, blue light, infrared light, scattering power, sauter mean diameter