Biofilters contain a mass of organic material (peat, compost, heather, bark or their mixtures) whose thickness is normally 1.0 – 1.5 m. In this substrate we select and develop a bacterial microflora able to degrade the molecules of the polluting compounds (organic and inorganic) contained in the air to be treated. In the biofilter therefore, pollutants are metabolized by bacteria that live in the bed. In detail, the air to be treated is collected by the environment to heal and sent to the scrubber that remove coarse particle. The scrubber also deals with humidification required for the development of the bacterial flora. The treated air comes out from the top of the scrubber and is sent inside the BIOCLEAN where there is the contact between the pollutants and bacteria that metabolize and turn them into odorless compounds (water and carbon dioxide).