Extraction is the way a cooker hood cleans the air in the kitchen by taking it outside the building. In this mode of operation, the appliance draws in the steam, grease and odours produced during cooking and permanently exhausts them outside via ducting. The ducting can be directed through a wall, the roof or into a chimney or central ventilation shaft. To use the extraction function, it is therefore necessary to have a construction opening and a route for the extraction pipe. Unlike recirculation, where the air is filtered and returned to the room, an extraction system gets rid not only of odours, but especially of moisture and steam. This effectively prevents condensation and possible mould growth in the kitchen. It is therefore a method that physically removes polluted air from the interior.