Dehumidification has long been an important industrial process, and its most extensive application is in the area of long-term storage and preservation of equipment and materials. Since moisture is the most important factor that contributes to material deterioration, both directly and indirectly, most materials can be preserved for a relatively long period in a low-humidity environment. In a large warehouse under relatively stable temperature conditions, it has been found that satisfactory long-term storage can be achieved if the warehouse is conditioned below 40% relative humidity.