Biofiltration is the biological degradation of gaseous pollutants and is one methods of deodorizing disruptive malodorous gases. Micro-organisms play a central role in this process. As a result of their work, non-toxic compounds are produced. Biofiltration belongs to the methods that are low to non-waste producing. This is an alternative to classical methods used so far. The research on the improvement of process parameters and increasing its efficiency is being carried out. The applied solutions referred to above still constitute unresolved problem and for this reason are seldom used. This article presents a mechanism for biofiltration of odorous gases. The article is devoted to the mechanism of malodorous gases biofiltration on the basis of a study carried out on the half-scale support.