Nowadays, sensing devices to monitor CO2 concentrations in human exhalation and the environment are essential to identify acceptable limits, including ventilation rates in workplaces in order to optimize the return to classrooms, laboratories and offices during the global coronavirus pandemic (SARS CoV‐2). In this study, we combined ZnO and MWCNTs to obtain a composite material and analyze their structural, and sensitive properties. In this work, pure ZnO nanostructures were synthesized by homogeneous precipitation with hexamethylenetetramine (HMTA) as precipitation agent. MWCNT used in the experiments were prepared by spray pyrolysis at 700 ºC. A nanocomposite of zinc oxide and multiwall carbon nanotubes (ZnO-MWCNT) was prepared by spray pyrolysis. The samples were tested in various concentrations of CO2 atmospheres ranging from 5 to 500 ppm. The Synchrotron X-ray (SXRD) measurements were carried out at room temperature confirming the hexagonal wurtzite phase of ZnO and composite. Raman analysis shows the detailed structural and significance differences between both ZnO and ZNO-MWCNT samples. SEM analysis indicated the rod-like morphology of ZnO structures and the agglomerates prisms of ZnO-MWCNT nanocomposite samples. Moreover, the CO2 detection properties like sensing response, response time, recovery time, repeatability, and stability for both the samples were obtained and discussed in detail. Finally, selectivity analysis with respect to acetone and ethanol were performed and corresponding gas sensing mechanisms are reported in this work.