A centrifugal fan or centrifugal blower is a pump or motor that moves air. It pulls the air inside the blower and then pushes it out at a 90º angle. The two main components of a centrifugal fan are the motor and the impeller. An impeller sucks or pulls air, in contrast to a propeller which pushes air. Some fans can pull and push air at lower than a 90º angle; these fans are called mixed flow fans. Centrifugal fans can either have no exterior housing or structure to offer protection or they can be built with some protective housing. As shown in the video below, there are five different types of centrifugal fans, which differ based on the type and shape of the fan blades. Each blade type varies in terms of efficiency – in other words, how fast the fan moves air through the duct or system where it’s installed. The most important thing to know is that backward curved blades are the most efficient, whereas forward curved blades are one of the least efficient types of fans. The video below discusses small low pressure centrifugal fans, which can move air quickly at a pressure between about 100 and 2, 000 pascals. A centrifugal fan is typically used for residential applications to move air through a duct in your home. Think of your air conditioning system, furnace, or range hood duct. You also might see these in commercial environments like your car wash. Once the wash is complete, large fans dry your car off in just seconds. Those fans are centrifugal fans. They take the outside air and move it rapidly, creating a pressure differential. So long as the pressure differential is maintained, the air continues to move, and your car dries off quickly. Centrifugal fans are also common in air conveyor devices, which use air to transport objects along a conveyor belt. This is something you might see in a factory or warehouse.