Although some desiccants are chemically inert, many are extremely reactive and require specialized handling techniques. The most common desiccant is silica, an otherwise inert, nontoxic, water-insoluble white solid. Tens of thousands of tons are produced annually for this purpose. Other common desiccants include activated charcoal, calcium sulfate (Drierite), calcium chloride, and molecular sieves (typically, zeolites).