The effect of Rh loading on CO sensing was studied for the case of In₂O₃. This was done by performing measurements with sensors based on loaded and unloaded materials that were performed at an operation temperature of 300 °C in the presence of low background oxygen concentration according to an experimental procedure that was demonstrated to help clarify the reception/transduction functions of loaded Semiconducting Metal Oxides (SMOX). The experimental investigation methods were DC resistance and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The results indicate that in the case of Rh₂O₃ loaded In₂O₃ the reaction primary takes place on the Rh2O3 cluster and the electrical properties of the In₂O₃ are controlled by the pinning of the SMOX Fermi-level to the one of the Rh₂O₃ cluster.