Rotary vacuum units are designed for pumping down air and nontoxic explosive and fire hazardous gases, which are non-aggressive to the pumped fluid and construction materials, vapors and gas-vapor mixtures which are precleared from condensed moisture and mechanical pollutions with oxygen content of air not more than 21 % . The maximum pumping speed is achieved in the inlet pressures range from 1,3·102 to 6,6 Pa (from 1 to 5·10-2 Torr). Also units can be used as pre-vacuum units for high vacuum pumps. Ambient class is UHL 4 according to all-Union State Standard 15150-69 for operation at the ambient and pumped medium temperatures from 283 to 308 K.