Evaporative cooling media are pads or panels that fit inside an evaporative cooler to provide a large surface area where heat is removed from warm air drawn into the cooler. Also called swamp cooler pads, they're made from natural or synthetic fibers that absorb water and wick heat from the air into the water to cool the air. They're used as replacements for pads that have deteriorated over time or become clogged with water scale or contaminated with bacteria or fungi.