Patent ID: 8826727

Claim:
A gas sensor for detecting concentration of NO x contained in an object gas, comprising: a first measurement chamber into which the object gas is introduced via a diffusion resistor section which limits flow of the object gas therethrough; a reduction section provided outside of the first measurement chamber and upstream of the diffusion resistor section, wherein the reduction section reduces NO 2 contained in the object gas introduced into the first measurement chamber to NO; a first oxygen pump cell having a first solid electrolyte layer and a pair of first electrodes provided on the inner and outer sides of the first measurement chamber; a second measurement chamber which is located downstream of the first measurement chamber and into which the object gas is introduced from the first measurement chamber; and a second oxygen pump cell having a second solid electrolyte layer and a pair of second electrodes provided on the inner and outer sides of the second measurement chamber, wherein a current corresponding to the amount of oxygen produced as a result of decomposition of NO contained in the object gas introduced into the second measurement chamber flows between the pair of second electrodes; wherein each of the diffusion resistor section and the reduction section is formed of a porous body having a large number of continuous pores through which the object gas flows; and the reduction section has a porosity higher than that of the diffusion resistor section.