MP402 combustible gas sensor uses multilayer thick film manufacturing process, in micro Al2O3 ceramic substrate on both sides respectively made heater and metal oxide semiconductor gas sensitive layer, packaged in metal shell. When the ambient air contains a detectable gas, the sensor conductivity changes. The higher the concentration of the gas, the higher the sensor's conductivity. A simple circuit can convert this change in conductivity into an output signal that is proportional to the gas concentration. This product has good sensitivity to methane in a wide range of concentrations, has excellent anti-interference ability, low power consumption, fast response recovery, good stability, long life, low cost, simple driving circuit and other advantages. It is mainly used in combustible gas leak detection devices for household, factory and commercial use, fire/safety detection systems.