A basic zirconia oxygen sensor was utilized to monitor the gas-solid oxidation reaction characteristics of metal/metal-oxide powder beds. The method described allowed for simple determination of chemical reaction rate constants for the oxidation reactions. The signal output of the sensor was analyzed for oxidation of the powder bed and diffusion of oxygen into the powder bed. The oxygen transport mechanisms occurring inside the sensor were described to further understand the signal outputs from the powder bed, and a discussion of relevant thermodynamic and kinetic theory was provided. Two metal/metal-oxide systems were examined using this device to demonstrate its performance. The simple Ni/NiO system was chosen to demonstrate feasibility, and the complex W/WO3 system was chosen to demonstrate versatility of the sensor. Combining the experimental data with relevant kinetic theory, chemical reaction rate constants were calculated from plots of sensor ocv versus time for each reaction step during the metal oxidation sequences.