Over the last two decades, the application of photodegradation for the destruction of a wide spectrum of organic compounds in air has gained considerable interest in abating environmental pollution. This paper presents the results of a fundamental study conducted to evaluate the gas phase oxidation kinetics of volatile organic compounds (VOCs) with respect to different parameters pertinent to the operating conditions of air stripping and soil vapor extraction processes. Photodegradations of three chlorinated VOCs: chloroform, carbon tetrachloride (CTC) and trichloroethylene (TCE), were investigated in a semi-batch reactor using a low-pressure mercury UV lamp. The effects of different experimental parameters, such as the initial concentrations of the VOCs, the reaction medium, relative humidity, light intensity, temperature and the effect of mixture that may influence the kinetics of the gas phase photodegradation were evaluated. Mechanisms of photodegradation as supported by the experimental data are also proposed.