In this study, piezoelectric quartz crystals are used as a gas sensor to investigate the detecting properties of titania nanoparticles for carbon monoxide and nitrogen dioxide gases. Titania nanoparticles are deposited on the surface of a piezoelectric quartz crystal by a gas condensation method. It is found that the amount of frequency change is dependent on gas concentrations at constant temperature. The amount of adsorbed carbon monoxide gas at 150°C hardly increases with increasing concentration, and the amount of adsorption is less than which at 200°C. The amount of adsorbed NO₂ also indicates similar results. The amount of adsorbed CO at 200°C is more than that of NO₂. The results are obtained from this study within one or two order difference in comparison with results in literature.