Abstract: A water recirculating system is which (a) water is continuously re-circulated through the system for the prime purpose of causing evaporation from the circulating water: and (b) such water is caused during its flow through an open part of said system through which part atmospheric air may flow to impinge on one or more solid surfaces whereby to increase the free water surface area available for evaporation and at a speed sufficient to release small water droplets from the water flow into the surrounding atmosphere. The system includes in serial relation with the water flow path a decontamination means (64) which comprises a chamber through which the circulating water may flow and in which there is provided an ion releasing means (80.