The kinetics of photocatalytic degradation of benzene in air has been studied on a standardized micro-pilot scale continuous flow apparatus. Both the yield of conversion of the reactant and the apparition of CO and CO2 have been monitored. The influences of concentration, light flux and temperature on the initial degradation rate have been studied. An apparent deactivation of the catalyst was identified as the formation of a resistant intermediate, which underwent a slow photocatalytic degradation leading to CO and CO2 as the main carbonaceous products of oxidation. A kinetic model has been derived which gives a satisfactory agreement with the experiments. The relative humidity is not of importance in the primary attack of benzene but it is of great importance in the degradation reaction. Increasing the relative humidity indeed allowed the conversion yield to be much increased due to acceleration in the degradation of the intermediate. (c) 2007 Elsevier B.V. All rights reserved.