Desiccants are hygroscopic powders and substances, such as silica and other deliquescents, that act as drying agents. They are used in desiccators to provide moisture free environments for items that can be damaged by moisture. Products differ by material and application. Most are used in compressed air drying applications. Other products related to compressed air dryers include regenerative desiccant air dryers, refrigerated air dryers, and membrane air dryers.