The complete elimination of odorants from the gases released into the atmosphere is a practically impossible task. This is mainly due to the fact that they are released not only during the technological process itself, but also during unloading, reloading, and transport, which are components of the technological line and also sources of emissions. It is not always possible to encapsulate these stages. Many gases belonging to the group of odorous compounds, characterized by unpleasant odors, have a very low detection threshold. Thus, for the odor to be imperceptible, the compound must be completely removed from the exhaust gas. This task would involve the necessity to take into account the complete air-tight sealing already at the stage of design and construction of the installation [T. Twardowski, A. Michalska, 2000, J. Warych, 1998]. This scientific article concerns the tests carried out in the composting plant in the field of protection against odors. In the experiment, a biofilter with a permanent filling with full process monitoring was used. The research was carried out to determine the process parameters for the real object.