Much work to improve the adsorption capacity of adsorbent has been done [91–94]. But the relationship of the adsorption capacity with the time or the recycle times has seldom been studied, especially for physical adsorbent. Since the information about adsorption deterioration of physical adsorbent including silica gel in adsorption refrigeration systems is hardly found to be reported at present, the exact reasons have not been determined. However, two research topics on adsorption deterioration of physical adsorbent should be executed. One is the study how the adsorption capacity deteriorates. The other is how to prevent such deterioration or to restore the adsorption capacity after adsorption deterioration. Some physical and chemical methods can be proposed: