Over the past two decades, biofiltration had been recognised as a reliable, environmentally friendly and cost effective technology for air treatment. In this study, ammonia was chosen as a model gas. Ammonia is a toxic and strong odour gas, which is produced in cases of ventilating intensive cattle breeding facilities, manure handling and waste composting, and is considered to be a major contributor to acidification and eutrophication of terrestrial and aquatic environments.