Basic Study on Fire Detection Using Air Temperature Monitoring with an Ultrasonic Probe

This paper reports on a fire detection method using an ultrasonic probe that measures room temperature based on the speed of sound. We establish the relationship between the time-of-flight (ToF) of acoustic waves and air temperature in the presence of flames. An ultrasonic probe consisting of a speaker and a microphone was developed, and fire experiments were conducted to measure the ToF at multiple flame locations. Results indicate that temperature increases caused by a flame can be detected using acoustic waves. However, the correlation between the transmitted and received waveforms decreases when the acoustic wave passes through the flame, thereby interfering with the cross-correlation function used in the ToF measurement. These findings suggest that the ultrasonic probe has potential for early fire detection in indoor environments by monitoring changes in ToF.