Abstract: Air conditioning apparatus ventilates room air with environmental air after the environmental air has been filtered, heated and humidified to appropriate levels. Environmental air is drawn into an intake duct, is passed successively through an air filter, an electric filament heater and is humidified by directing the air stream through a moving evaporator belt which is saturated with water from a water tank which is automatically controlled by a humidistat. The humidity level and temperature are automatically maintained by means of the humidistat and air temperature sensor.