MP-7 adopts advanced planar construction production technics, using MOS material formed by micro AL2O3 ceramic tube and heater, electro-down-lead be fetched out, and are fixed into a metal base and cover. Adopting low and high temperature circling detection: when low temperature （VH=1.5V）, it detects CO, Conductance of sensor bigger along with CO concentration in air; When high temperature（VH=5.0V）, clean other gases, using simple circuit could change the conductance, change it to be output signal which relatively to the gas concentration.