Apart from the exhaustion of the humidity, these extractor fans for sale have many other characteristics that will amaze you. As a basic guide, if you install a fan into a kitchen or utility room it should be a 6 inch, or 150 mm, fan, and for a bathroom or toilet, it should be 4 inches or 100 mm. This measurement refers to the diameter of the spigot, or pipe, that sticks out of the back of the fan.  What should be the size of the fan? When you've chosen what size fan you require for the room being referred...