Controlling the environment in an indoor swimming pool hall is a challenge. Evaporation from the heated pool water combined with chlorine-based water purifiers produces a potentially corrosive atmosphere. Moreover, attempts to control humidity by increasing ventilation in the pool hall carries a cost penalty.Most public swimming pools are heated to 28°C, or lower for competitive swimming. Though the rate of evaporation can be minimised by holding the air temperature at 2°C above the water temperature during busy conditions, 20kg/hour of water vapour will still be given off from every 100 square metres of surface area. For a typical 33 metre pool, this means that over 100kg of water vapour will be created every hour. At 28°C water temperature, this represents 66kW of heat energy lost. With many public pools requiring refurbishment earlier than expected due, in part, to the hostile indoor environment, owners and managers are increasingly turning to Calorex Delta and HRD systems to provide optimum environments for new and refurbished pools.