This is the first in a series of articles on several new energy-saving technologies evaluated in a recent U.S. Department of Energy report. It is common practice in commercial building air conditioning to combine ventilation makeup air with return air from the building, condition (cool or heat) this air as needed, and distribute the conditioned air to the interior space, with or without zoned temperature control. Dedicated outdoor air systems (DOAS) condition the outdoor ventilation makeup air separately from the return air from the conditioned space.