There were considered some topical issues of choice of optimal adjutage design for process performance with respect to biological purification of gases from harmful pollutants (volatile organic compounds) in biological filters. Biofiltration process is described fully from a perspective of hydrodynamics, there are emphasized the main stages of the process for revealing of rate-determining step. There was made comparison of different types of adjutages (irregular, regular, combined) and their characteristics from viewpoint their applicability with respect to process of biological purification of gas, including odor control. On the basis if obtained experimental data, as well as elaboration of known data of other researchers made generalization of results on geometric characteristics of adjutages’ different types, for the purpose of identify of optimum performances, as well as development of effective type of adjutage for biological filter.