The paper considers the issue of improving the aerodynamic characteristics of ventilator units by modification of the structural elements for connecting radial ventilators to ventilation system. It is noted that the peculiarity of a diffuser, placed directly after the ventilator outlet pipe, is the formation of non-uniform and asymmetric velocity field in its inlet section, which causes an increase in pressure losses. Recommendations for increasing the efficiency of diffusers are considered. In the Flow Simulation module of the SOLIDWORKS software package, numerical simulation of the turbulent flow in the construction elements connecting outlet pipe and air duct was carried out, on the basis of which it is recommended that the leveling plate be made compound with the different angles of inclination of its parts, when installed in the asymmetric diffuser. Based on our own experimental studies of the aerodynamic characteristics of ventilator unit, recommendations are given for choosing the geometric parameters for placing the leveling plate in a diffuser, which ensure the maximum increase in the capacity of radial ventilator. The use of ventilator units with improved aerodynamic characteristics makes it possible to increase the energy efficiency of ventilation systems and reduce their operating costs.