Biological deordorization receives attracting attention as an alternative method to physical and chemical treatment, mainly because of its energy-saving and easy maintenance features. A biofilter packed with scoria, and inoculated with Bacillus sp. as H2S oxidizer was used to remove hydrogen sulfide in the air stream. Various tests have been conducted to evaluate the effect of H2S inlet concentration and EBCT (Empty Bed Contact Time) on H2S elimination, and to determine the maximum elimination capacity. The pressure drop in the biofilter packed with particles of size range from 5.6 to 10 mm was 13.4 mmH2O/m at a representative gas velocity of 0.25 m/s. Biofilter showed the stable removal efficiencies of over 99% under the EBCT range from 8.2 to 60 sec at the 250 ppmv of H2S inlet concentration. When the retention time was reduced to 5.5 sec, the H2S removal efficiency decreased by about 10 percent and the H2S elimination capacity was 254 g-H2S/m(3)/hr. The removal efficiencies of over 99.9% were observed in the range of inlet H2S concentration from 30 to 1,100 ppmv at a constant gas flow rate of 15.2 L/min (linear velocity, 0.04 m/sec).