Oxygen permeability data, vital parameters for understanding and modeling the thermooxidative degradation of polymers, have been determined for various elastomers. Using a novel experimental setup, oxygen permeability through sheet materials was measured for elevated temperatures up to 225 degrees C. Under these conditions oxygen can react with the polymer reducing the effective O-2 flux. Knowing the relevant oxidation rates makes it possible to correct the permeability measurements for thermal oxidation occurring during permeation. A theoretical model using iterative data processing to determine true permeability data was developed to compensate for the oxidative loss of oxygen. The applicability to data collection and mathematical treatment for a range of materials is demonstrated. All permeability measurements exhibit curvature for an Arrhenius plot with activation energies being highly dependent on temperature.