An air-conditioning system for a work space in which recirculated air is mixed with outside air and the mixture is passed through a washer. The controls for the system include an absolute moisture controller in the primary air supply downstream from the air washer, a direct-acting humidistat for the room air and a reverse-acting thermostat for the room air. The proportional output signals of the thermostat and humidistat are fed to a high-and-low signals selector which transmits the higher of the two signals to a heating control for the recirculated air and the lower of the two signals to a throttling valve for the air washer. In normal operation, the air washer is fully throttled before the heating control is activated to supply heat to the recirculated air since the heating control is responsive to a pressure above the range of pressures which are effective to modulate the washer sprays. Under special conditions, the throttling of the spray in the air washer is reduced after the heating control is activated so as to increase the humidification effected by the air washer.