Abstract: An air handler for conditioning recirculated or make-up space air and including a conditioning chamber and air flow means for moving air therethrough. An evaporative air cooler of the air handler has an air permeable pad extending across the chamber and a fluid spray system for maintaining a moist condition of the pad. The spray system is constructed and arranged to discharge cooling fluid spray patterns covering the upstream side of the pad in a plurality of predefined zones, and further includes a plurality of moisture sensors positioned at predetermined locations adjacent to the downstream side of the pad. A controller is responsive to sensed moisture conditions for controlling the activation and deactivation of the spraying mechanism to maintain at least a preselected moisture content in the pad.