Carbon monoxide is a poisonous and hazardous gas and sensitive sensor devices are needed to prevent humans from being poisoned by this gas. A CO gas sensor has been prepared from WO3 synthesized by a sol-gel method. The sensor chip was prepared by a spin-coating technique which deposited a thin film of WO3 on an alumina substrate. The chip samples were then calcined at 300, 400, 500 or 600 ?C for 1 h. The sensitivities of the different sensor chips for CO gas were determined by comparing the changes in electrical resistance in the absence and presence of 50 ppm of CO gas at 200 ?C. The WO3 calcined at 500 ?C had the highest sensitivity. The sensitivity of this sensor was also measured at CO concentrations of 100 ppm and 200 ppm and at operating temperatures of 30 and 100 ?C. Thermogravimetric analysis of the WO3 calcined at 500 ?C indicated that this sample had the highest gas adsorption capacity. This preliminary research has shown that WO3 can serve as a CO gas sensor and that is should be further explored and developed. Copyright 2014 Higher Education Press and Springer-Verlag Berlin Heidelberg.