This paper presents a case study of a commercial biofilter, treating air streams contaminated with several odorous compounds including dimethyl sulfide, ammonia, methanethiol, hydrogen sulfide and ethylamine. The biofilter is packed with a proprietary wood-based (BIOMIX(TM)) medium which is designed to provide a good biological environment, pH buffer capacity, low pressure drop and resistance to compaction. This commercial biofilter treats a contaminated air volume of 15 000 actual cubic feet per minute (acfm) from a meat rendering and wastewater treatment operation with a 30-s empty bed residence time. The case study includes a novel gas sampling procedure and characterization of biofilter air streams through a mobile Fourier transform infrared system and olfactometer analysis. The results confirmed the good distribution of air, moisture and bacterial population across the medium. Four years of consistent performance of this commercial biofilter with >99% removal of 24500 odor units demonstrates that biofilters can be successfully applied for the removal of highly odorous gaseous sulfur compounds.