The discoloration of polyolefins has been extensively studied. The key mechanism of discoloration includes oxidation of polyethylene and/or oxidation of hindered phenolics used as antioxidants by oxygen or nitroxide pollutants from hydrocarbon combustion, e.g., internal combustion engines, or methane- or propane-fired heating systems. This seminar will present an open-literature review of the discoloration mechanism, the effects of the chemical structure of antioxidants on discoloration, and the prediction of gas fading during storage, with a comparison between two lab-scale test methods, using the kinetics of the reaction between commonly used hindered phenols and nitroxide.