An apparatus employing a thermal conductivity bridge to compare the oxygen concentration in a gas stream before and after reaction with an inductively heated metallic pellet is described. The measurements are continuous and sensitive to rates of oxygen consumption of 10−6 g/min. The method has been used to study oxidation of silicides, borides, carbides and pure metals in the range 900°–2100°C. Results reported here on the oxidation of copper at temperatures around 1000°C are in reasonable agreement with results obtained by more conventional methods in other laboratories, and with the Wagner theory of parabolic reactions.