Adsorption of molecules onto solid surfaces can be classified into physisorption and chemisorption. Physisorbed molecules are so weakly bound to surfaces that adsorption and desorption can proceed reversibly even at room temperature. By contrast, chemisorption is accompanied by chemical bond formation, and higher temperature are necessary for desorption. Solid gas sensors are normally based on chemisorption for modification of the electronic band conduction. We found that copper nanocables sheathed in carbon can detect physisorbed oxygen at room temperature by just measuring electric resistance. The sensing principle based on hoping conduction is specific to nanomaterials and enables detection of physisorbed oxygen.