Currently, semiconductor gas sensors are among the most common types of sensing devices for detecting dangerous and toxic gases in the atmosphere. However, the problem of improving their characteristics should be solved for practical application. In this work, techniques have been developed to improve the response of sensors based on zinc oxide nanowires. The first technique is to modify the chemical composition of the nanowires by forming a shell of ternary Zn-Sn-O and Zn-Fe-O systems on their surface. Another approach is to control the surface concentration of oxygen vacancies by adding sodium bromide during the synthesis of zinc oxide nanowires. The surface chemical composition and the sensor properties of the samples were studied. It was found that the sensor responses of samples of ternary oxide systems and zinc oxide sample with a high content of oxygen vacancies exceed the one of the initial zinc oxide nanowires. The results are analyzed in the terms of the interaction of reducing gases with metal oxides.