Abstract: A moisture control device for drying air, having an enclosed housing including an inlet and at least one restricted outlet. Contained within the housing, in between and on opposite sides of the inlet and outlet, are first and second desiccant columns, each containing a desiccant material. An inlet plenum is located between the inlet and the desiccant columns, and the discharge plenum is located between the restricted outlet and the desiccant columns, with the inlet and discharge plenums communicating through the desiccant columns. A valve damper is pivotally supported within the inlet plenum having one end extending across the inlet to alternately direct air into the housing by a blower into one of the desiccant columns. Pivotal exhaust doors are actuated by the damper to direct dry air into the opposite desiccant column, regenerating that column, before exhausting the air out of the housing.