The S600-ExIR4 four-wavelength point infrared flame detector contains four infrared sensors and optical filters. The main sensor has the highest sensitivity to the CO2 emission spectrum (4.4 μm) generated by the combustion of hydrocarbons, and the other three infrared sensor pairs The detection of ambient light and background light interference from thermal body radiation. The detector has multiple signal processing algorithms, combined with the logical comprehensive judgment of the flame flicker frequency, to maximize the suppression of false alarms and the best fire detection performance. The special fire signal processing method and multi-sensor detection technology greatly improve the sensitivity and response time of the detector. The detector is suitable for liquid and gas fires, open flames with smoke and places where deflagration occurs.