The room-temperature nanosensors are demanded from different fields, such as rapid detection of hazardous, explosive and nocive gases, compounds and various risky nanomaterials. Due to their huge surface-to-volume ratio and high crystallinity, the one-dimensional (1- D) semiconducting oxide nanostructures, such as nanowires have attracted great interest toward their integration in modern sensing micro-devices and nano-devices. In this work, we investigated performances of individual Pd-, Au-nanoparticles functionalized zinc oxide nanowires integrated into nanosensor devices using dual beam focused ion beam/scanning electron microscopy (FIB/SEM) and investigated them as gas nanosensors at room temperature. Important parameters as length, diameter and relative humidity (RH) on the gas sensing properties were studied in detail. The obtained results demonstrate that thin Au/ZnO nanowire (radius of 65 nm) have a gas response of about 8 to 100 ppm of H2 gas which is higher compared to ~ 1.2 for those with a radius of 130 nm. The corresponding gas sensing mechanisms are tentatively proposed for each type of nanodevices. The proposed nanosensors are essential for next understanding the role of noble metal nanoclusters on semiconducting oxide nanowires and contribute for a design of modern room-temperature gas nanosensors.