When comparing superheated steam and dry air in a drying process a temperature has been found, at which the drying rates into the gases compared are equal. This temperature is called the inversion temperature. Many different values for the inversion temperature have been reported in the literature in the last years. This paper presents a model to calculate the inversion temperature. The model is based on the equations describing coupled heat and mass transfer and the calculated results are in good agreement with experimental findings without the need of fitting parameters to the data. The range of inversion temperatures found can be explained with the theory of the model.