Abstract: An air conditioning system is disclosed for adjusting air temperature and humidity to a predetermined level for the air supply to a paint spray booth. The system includes a multi-section sprayed surface heat exchanger combined with a bypass passage such that a portion of the air flow to be conditioned passes through the multi-section heat exchanger and the remainder of the flow bypasses the same, and is recombined and mixed downstream with the conditioned air to produce a mixture which is at the proper dry bulb temperature and relative humidity. Each multisection heat exchanger may be shut off to increase the proportion of bypass flow. Modulation of the cooling and heating effect of each of the heat exchangers is achieved by modulating valve controlling the flow of heating or cooling medium. Similarly, the humidification effect is controlled by valving controlling a number of water spray nozzles.