Cooling towers and evaporative condensers.

By 31 October 1978 there had been four confirmed instances where the Legionnaires' disease bacterium had been isolated from water samples taken from cooling towers or evaporative condensers located near the site of an epidemic of Legionnaires' disease. These devices are widely used to reject unwanted heat into the atmosphere and vary greatly in size and configuration. However, the operation of all towers and condensers depends on intimate contact between the circulating water and ambient air. Airborne contaminants in the vicinity of these devices are likely to be absorbed to some degree by the circulating water. The airstream leaving a cooling tower is saturated with water vapor and may also contain a relatively minute portion of the circulating water in the form of fine droplets known as drift. It is common practice to bleed a small portion of the circulating water, including all contaminants, from the tower into a storm sewer, sanitary sewer, or even a nearby body of water.