Secondary pyrolysis of vaporized unsaturated hydrocarbons in the presence of water vapor and oxygen gas was studied, using toluene and benzene as tar-derived species and/or volatile organic compounds (VOCs). Toluene and benzene have been chosen as model formulas for reactive one-ring species determined from tar constituents present in the gas derived from gasification and pyrolysis technologies. The experiments were performed in a plug-flow-reactor at atmospheric pressure via the introduction of dynamic steady-state assumptions.. a temperature of 1098 K: and residence times of tau less than or equal to 5 s. The gas-phase molar ratios were [H2O + O-2](air)/[C7H8] = 3.52 and [H2O + O-2](air)/[C6H6] = 3.53 in toluene and benzene, respectively. The experimental observations have been evaluated in terms of a chemical kinetics model. The proposed model interpreted the experimental trends and reproduced the experimental data. Benzyl radical species (C7H7) can be considered as a key component of the thermal dissociation of toluene. Comparison of the results from computer simulations shows that hydrogen influences the destruction of toluene. In the presence of water vapor and hydrogen, the intermediate compound C7H7 undergoes decomposition. During VOC dissociation, the oxidized environment enhances the formation of H-2, CO2 and CO2.