In fluidized bed coating, the system will always evolve towards an equilibrium state when environmental and process variables are all constant: the thermodynamic operation point. This condition of steady-state is often only described by a temperature measured in the bed or at the outlet and this value is used by the operator to adjust the spray rate if necessary from batch to batch. Nevertheless, the humidity should also be taken into account when characterizing the operation point. The importance of this defined state of the system is often underestimated. From the viewpoint of energy consumption, the thermodynamic operation point will determine the thermal efficiency of the drying process. Moreover, product quality characteristics (e.g. coating efficiency, coating quality, risk of agglomeration) are often related to this steady-state condition. Figure 4 illustrates how the different variables affect the thermodynamic operation point. Some of the process variables and ambient temperature also indirectly influence the thermodynamic operation point via the magnitude of the total reactor heat loss, comprising convective and radiative losses