Bathroom Fans come in two types. Axial fans extract air through the impeller which is parallel to the shaft around which the blades spin. These are the most common of domestic wall fans and are perfect for use in the bathroom, toilet or smaller rooms where it needs to be installed in a window or ducted straight through the wall. The standard size impeller for this type of extractor is normally around four inches or possible six inches if it is a large space. They usually come in two different voltages, 240 volt for mains or 12 volt for low voltage applications. Different switching options are common with features like pullcords, himidistats and timers which can be used to activate the fan.