FeO monowire structures were constructed and optimized using density functional theory (DFT) to study the adsorption behavior of CO and HCHO gas phase molecules. The adsorption behavior of the target molecules was studied in terms of adsorption energy, charge density and the reaction time of the FeO monowire devices. Also, FeO monowire molecular devices are constructed to study the sensitivity of the devices towards CO and HCHO molecules using non-equilibrium Green’s function (NEGF) with density functional theory. The zero bias electronic transport properties confirm the adsorption of the CO and HCHO on the FeO monowire devices. From the V–I characteristic and the differential conductance calculations, the FeO monowire device is more sensitive to HCHO than CO molecule. However, the CO-adsorbed FeO monowire device exhibits high order of NDR behavior and can be used as a functional group for fabricating data storage device based FeO monowire.