There are two ways in which hoods manage the vapour and grease produced when you cook. In recirculation mode, cooker hoods use a fan to suck in vapours and pass them through a filter made from metal (permanent filter) or fleece (disposable filter). This removes grease and absorbs odours with an integrated active carbon filter. The cleaned air is then returned to the room. In extraction mode, cooker hoods use a fan to suck in vapours and pass them through the same filters, but the filtered air is then extracted outdoors. For chimney hoods, the exhaust air can be routed through the wall behind the hood or through a lateral extractor duct.