$NO_x$ sensing properties of $Ba_2WO_5$ at elevated temperatures were investigated. $Ba_2WO_5$ sintered at 800℃ exhibited outstanding sensitivity to both NO and $NO_2$. When operating temperature was 500℃ the sensitivitis to NO 200 ppm and $NO_2$ 80 ppm were 47 and 29, respectively. The sensitivity increased almost linearly as the concentration of NO or $NO_2$ increased
The NO sensitivity strongly depended on the coexistent $O_2$ concentration. As $O_2$ concentration increased the NO sensitivity improved. In addition, interference effect by other gases, CO and $H_2$, examined. CO interference effect is rather serious but $H_2$ didn't interfere almost to NO sensing property.
