Strictly speaking, desiccant has no shelf life, because its shelf life is its moisture absorption rate. If the moisture absorption is saturated, it may have no effect in a few hours. In terms of silica gel desiccant, its moisture absorption rate is about 30%, that is to say, it will lose its effect after absorbing 30% of its own weight of water. The moisture absorption rate of calcium chloride desiccant is up to 300%, and the effective moisture absorption can be up to 90 days. Therefore, the desiccant generally depends on the moisture absorption rate rather than the shelf life. If it is a desiccant in sealed packaging, it can be placed for a longer time, but no matter how sealed the packaging is, there will be some air, and there will be moisture in the air.