The transient behavior of a hybrid system composed of biofilter and photo-catalytic reactor was observed at the height of each sampling port to treat waste-air containing ethanol. The biofilter packed with mixed media (of granular activated carbon and compost) was inoculated with a pure culture of Burkholderia cepacia G4 and Pseudomonas putida, while a photo-catalytic reactor was composed of 15W UV-A lamps and annular pyrex tubes packed with glass beads coated with sol type of TiO2 before calcination. The maximum elimination capacities of toluene and ethanol turned out to be 130 g/m3/h and 230 g/m3/h, respectively, which were greater by 40 g/m3/h and 130 g/m3/h, respectively, than those from the experiments performed with a biofilter only. Thus, the maximum elimination capacities for toluene and ethanol increased by 44% and 130%, respectively, by use of a hybrid system. The photo-catalytic process contributed to the maximum elimination capacities of hybrid system on toluene and ethanol by 30.8% and 56.5%, respectively, which contributions for the elimination capacities on toluene and ethanol were allocated indirectly by 25.4% and 44.3% as well as directly by 5.4% and 12.2%, respectively. Direct contributions of photo-catalytic process were 17.5% and 21.5% to the increments of the elimination capacities on toluene and ethanol, respectively, while its indirect contributions were 82.5% and 78.5% to those on toluene and ethanol, respectively.