The fan-coil type of terminal provides direct heating or cooling of the room air. A supplementary constant volume air supply provides the necessary ventilation. Basic elements of fan-coil units are a finned-tube coil, filter, and fan section. The fan circulates air continuously from the space through the coil, which contains either hot or chilled water. A cleanable or replaceable filter, located upstream of the fan, prevents clogging the coil with dirt or lint entrained in the recirculated air. It also protects the motor and fan, and reduces the level of airborne contaminants within the conditioned space. Where units do not have individual outside air intakes, means must be provided to introduce pretreated outside air through a duct system engaging each room or space.