Abstract: A system for the sorption treatment of fluids comprises a sorption vessel having an exterior wall, a fluid feed entrance, a fluid product exit, and an internally-disposed sorbent material bed. The system further includes an element for determining a thermal characteristic of the sorbent bed, which element comprises a sensing element for generating a signal indicative of a temperature of the sorbent vessel exterior wall, and control means for processing that temperature-representative signal. The system further comprises an output element for generating a signal indicative of the particular thermal characteristic. The system has application in improving the efficiency of adsorption vessels, solids drying apparatus, and like devices. Moreover, the system may be utilized as a diagnostic device for such apparatus.