Application Research Of CO Gas Detection Based On TDLAS For Early Fire Detection

With the development of science and technology,various types of fire detectors have been developed.These fire detectors have realized fire warning and protected people's lives and property.This paper introduces the development of fire detectors,and the advantages and disadvantages of different types of fire detectors are analyzed.Aiming at the poor stability of traditional gas fire detectors,the Tunable Diode Laser Absorption Spectroscopy is used to detect the concentration of CO in early fires,which improves the sensitivity and stability of fire gas detection.In this paper,the principle of absorption spectroscopy is introduced,and the characteristics of direct absorption spectroscopy,wavelength modulation spectroscopy and frequency modulation spectroscopy are analyzed.Finally,the Tunable Diode Laser Absorption Spectroscopy system is used to detect CO concentration in early fires.The system is introduced from three aspects:optics system,pneumatic system and circuit system.The Herriott multipass optical device in optics system is used to increase the effective optical path which improves the detection sensitivity.In the aspect of pneumatic system,a fire experiment box based on Froude model was designed and fabricated,and the pneumatic systems for concentration calibration and fire experiment were built.The harmonic detection in the circuit system are used to reduce the noise.Experiments show that the minimum detection limit of the system is3.7575×10^-6.Finally,fire tests were carried out on common combustibles such as beech,cotton,paper,polyvinyl chloride and plastic foam,and the CO concentration of these combustibles during early fires were measured and analyzed.