Abstract: A temperature and humidity control system for natatoriums. The system provides a constant volume of air circulation which is used to control temperature and humidity in the natatorium while inhibiting the accumulation of moisture on the surfaces defining the natatorium. Usually, ambient air is introduced into the system and moisture latent air discharged from the system under controlled conditions. When the humidity of the ambient air is too great the system operates in a self-contained cycle. Return air from the natatorium flowing through the system is treated to maximize its relative humidity. Subsequently, it flows across a cooling coil. This cooled air flows through a heat exchange module where it is placed in exchange relationship with the air being drawn from the natatorium. It cools the air drawn from the natatorium to maximize its relative humidity and this air in turn flows across the refrigeration coil removing substantial quantities of moisture.