To avoid getting dust inside RACKs it was decided to close them as hermetically as possible and provide the closed air loop venntilation. In each cabinet there are temperature and humidity transducers , fans modules and radiators. Using RS-485 standard based on the MODBUS protocol and modules of logic outputs, fans are being switched on and off depending on temperature inside each RACK and their work time. The cabinets are working in master-slave configuration. Software is easy to adjust to load settings from database.