Based on theoretical and experimental tests it was determined that the thermodynamic balancecondition in the working space of air-handling units (AHUs) of heating, ventilating and aircondltioningsystems (HVAC systems) is entirely defined by the humidity potential of thefinal parameters of air and water: @ = constant . This makes it possible to put forward anew thermodynamic method for the analysis and calculation of heat and moisture exchange inAHUs of HVAC systems [2,3]. It was established, that condition "@ = constant of finalenvironmental parameters is an index of the optimal mode of operation of the AHU, inwhich high thermodynamic efficiency is achieved in the processes of heat and moistureexchange. The data collected made it possible to work out a new method of air parameterscontrol for processing in AHUs. The features of processes of heat and moisture exchange inAHUs are considered in this paper, and also the results of the proposed method of regulatingthe moisture content of incoming air.