Desiccant

A material, such as silica gel, that is able to absorb moisture from the air. When precision equipment is stored, bags of silica gel are packed with it. The silica gel absorbs moisture from the air and prevents the moisture damaging the equipment. In pneumatic power systems, the high-pressure compressed air passes through a desiccant which absorbs all the moisture in the air. If moisture were left in the air, it would freeze when the air expands and its temperature drops.