Biofilter technology is used for high concentrations of malodorous compounds and water soluble volatile organic compounds (VOCs), including sulphur compounds such as hydrogen sulphide. The contaminated air passes through a moist media bed, which acts as a host for a layer of biofilm. Microorganisms, fungi and bacteria inhabit the biofilm and degrade the odorous compounds, significantly reducing their level in the exhausted airstream.

Biofilters can be stand-alone, or often combined with dry media such as activated carbon for polishing.