Evaporative coolers, or "swamp coolers" as they are often referred to, are devices used for air conditioning or cooling in drier climates where dry-bulb temperatures of 90°F or more occur simultaneously with wet-bulb temperatures of 75°F and below. The wider this gap, the greater the opportunity for efficient evaporative cooler applications. They accomplish cooling by adding moisture or humidity to the ambient air. Water is allowed to flow over a media or evaporative pad while warm, dry ambient air is forced across the wet media. Evaporation is induced, and the dry ambient air is cooled. Evaporative coolers can be used to directly cool ambient air for comfort air conditioning, or used as "pre-coolers" on mechanical air conditioning (air-cooled) condensers. As water is brought into an evaporative cooler and evaporated, its scale-forming minerals remain behind in the recirculating water and begin to "fall out" or precipitate as scale, plugging the media, reducing evaporation space for the water as well as air flow. In turn, the equipment's efficiency is reduced and the desired cooling is not achieved. Unfortunately, the process continues until the media pad becomes a "solid piece of scale."