A NASICON based amperometric sensor was designed for the detection of total NO chi (NO + NO2) in air. To make the device sensitive to both NO2 and NO, the sensing electrode (Au) was covered with NO oxidation catalysts. With the sensing electrode potential fixed at - 150 mV vs, reference electrode (Au), the device attached with double catalyst layers of WO, and Pt(0.5 wt%)-loaded SiO2 produced current response proportional to the concentration of NO2 or NO up to 1 ppm at 150 degreesC. In addition, the proportionality constants (sensitivity) were almost the same to NO and NO2. The current responses were barely affected by the coexistence of CO2 or H2O.