MOS multi-cyclones are a sort of serial dust extracting units. The comprise many little de-dusting cells fastened horizontally in a housing of a dust extracting unit. These so called "vibration generators" are made of a cast-iron. Since we apply series of small cells to erect a dust extracting unit, we increase in efficiency of the de-dusting process (it grows up as the diameter of the dust extracting unit goes down). Proper number and configuration of cells ensures stable operation of the installation and, at the same time, high efficiency of preliminary de-dusting process. What is important, the MOS dust extracting units are of small dimensions (e.g. compared to cyclones) and they increase in dimensions of an entire system slightly. Standard series of types of MOS multi-cyclones comprises their sizes starting from 1 cell up to 40 cells, efficiency range from 3000 to 120 000 m3/h.