The Natural Draught Cooling Towers are an open, direct-contact system. These work using a heat exchanger, allowing hot water from the system to be cooled through direct contact with fresh air. To increase the heat transfer surface area, hot water is sprayed from nozzles within the tower. This increases both the temperature and humidity of the air in the tower. The warmer, moister air moves to the top of the tower, while the cold water is collected at the bottom. The fresh air supply is located in the bottom of the Natural Draught Cooling Towers.