The removal of hydrogen sulfide (H₂S) from contaminated airstream was studied in a biotrickling filter (BTF) packed with open-pore polyurethane foam as a carrier of Thiobacillus thioparus (DSMZ5368) with counter current gas/liquid flows. The effect of operating parameters on BTF performance was studied. Experiments were performed at different Empty Bed Residence Times (EBRT) from 9 to 45 seconds, and different initial H₂S concentration from 25 to 85 ppm. The results showed reasonable performance of the BTF, in H₂S removal from the synthetic gas stream. However, the performance was somewhat lower than other studies in BTF in which either Thiobacillus thioparus with other packings or polyurethane foam with other microbial cultures were used. The effect of liquid recirculation rate (LRR) in the range of 175-525 ml/min (0.46-1.34 m/h) on BTF performance was also studied. Results showed that increasing LRR from 175 to 350 mL/min resulted in significant enhancement of H₂S removal efficiency, but further increase in LRR up to 525 mL/min had an insignificant effect. H₂S elimination at different heights of the bed was studied and it was found that decrease in EBRT results in more homogeneous removal of the pollutant in BTF. Determination of microbial species in the BTF after 100 days performance showed that during BTF operation the only H₂S degrading specie was Thiobacillus thioparus.