Smoldering fire detection using low-power capacitive MEMS hydrogen sensor for future fire alarm

Abstract

In this study, we demonstrated detection of a smoldering fire using a low-power hydrogen sensor. To detect the low levels of hydrogen gas generated by smoldering fires, we used a capacitive MEMS hydrogen sensor with a microheater. The microheater accelerates the reduction of palladium oxide on the surface of the sensing film by hydrogen. Thus, more hydrogen is entrapped within the sensing film, and the sensitivity to ppm amounts of hydrogen is improved. The low thermal capacity and high thermal resistance of the structure enabled localized heating of the sensitive film at high speed (1 ms), thereby achieving sub-mW low power consumption by intermittent sensing. The fabricated hydrogen sensor was installed in a small wireless module and placed on a ceiling 3 m from a smoldering cotton fire. Our hydrogen sensor successfully detected 66 ppm hydrogen generated by the fire, and also detected the decrease in hydrogen by room exhaust.