Air conditioners move warm indoor air over refrigerant-filled coils to remove heat for cooling one or more rooms in a building. They also remove moisture from the air to make a room feel cooler than a humid room of the same temperature. These units keep people and equipment cool in commercial and residential settings and are ideal for cooling hot, humid areas where evaporative coolers would be ineffective. Ceiling, window, and wall air conditioners can be used as the primary source of cooling for a single room or as backup or supplemental cooling for a central air conditioning system. Central air conditioners provide cool air to multiple rooms in a building. Portable air conditioners are used for cooling a room or spot cooling people or processes.