The paper will cover new developments and new applications notably in solid waste composting plants and industrial installations. The experience gained from the installation of over 300 biofilters, primarily in municipal and industrial wastewater treatment plants during the 1990s, means Bord na Móna is able to talk knowledgeably about the routes to successful biological air treatment and the pitfalls to be avoided. Since the mid 1990s, Bord na Móna has concentrated its efforts on process development for VOC and industrial applications. New applications include treatment of airstreams containing high concentrations of H2S, ammonia, VOC or indeed a combination of all three. Success in biofiltration is closely linked with in-depth analytical process engineering, accurate characterisation of waste gas streams, control of process conditions for optimisation of biological activity and the physio-chemical properties of the filter media. Particular attention is given to the successful application of biofilters for extremely high concentrations of sulphur compounds and the increasing use of biofilters for VOC elimination.