A swamp cooler, also known as an evaporative cooler, is a device used for cooling a home in the place of an air conditioner. Swamp cooler units are often used in the Southwest, in dry states like Nevada and Arizona.
The swamp cooler usually sits on the roof of a house and has a duct that leads down into the home. A swamp cooler essentially contains a fan and pads soaked with water. There is a reservoir of water at the bottom of the swamp cooler. To keep the swamp cooler pads wet, a water pump carries the water to the top of the swamp cooler, where it trickles onto the pads, wetting them.