Emissions from industrial sources are characterized by a large variety of pollutants including inorg. compds. of high toxicity. Very little is yet known regarding the lifetime and mechanism of the photo-oxidn. of such species in the troposphere. As part of an investigation of the reactive removal of such emissions by homogeneous gas reactions, direct rate measurements were made for the reactions of OH radicals with C2H4O (ethene oxide), PH3, and HCN by using an excimer laser photolysis/resonance fluorescence system. These rate consts. are used to propose probable oxidn. mechanism of these species applicable to tropospheric conditions.