Abstract: Described herein is an apparatus and method for removing moisture and/or sorbates from airstream and/or other fluid. The system comprises a preconditioning desiccant wheel and a main desiccant wheel. The preconditioning desiccant wheel comprises of at least two first sectors for allowing air to pass therethrough, including a first process sector and a first reactivation sector. The main desiccant wheel comprises of at least three second sectors for allowing air to pass therethrough, sequentially including a second outside air sector, a second process sector, and a second reactivation sector. The ambient airstream is sequentially dehumidified in one of the at least two sectors of the preconditioning desiccant wheel and the outside air sector of the main desiccant wheel, before being at least partially supplied for reactivation to the reactivation sector of the main desiccant wheel.