However, in a recirculating air system, the air remains inside the room. The extractor draws away the air that is filled with cooking odours and grease molecules, It is then filtered and returned into the kitchen as fresh, clean air. In addition to the grease filter, an activated charcoal filter is also necessary.
Once, the grease and food particles are removed by the grease filter, the activated charcoal then absorbs the remaining food odours from the air. The recirculating air system blocks any odour particles re-entering the room. When used over a long period of time, the extremely large filter surface of the activated charcoal gradually absorbs less and less odour molecules, until none are absorbed at all. For this reason, the recirculation filter must be changed regularly. Please see the service life or operating hours in the operating instructions of your cooktop extractor system. Depending on the system, the BORA recirculation filters have different service lives of between 1 and 2 years. This means that they work for a comparatively long time before a filter change is necessary.
Compared to kitchen exhaust air solutions, recirculating air solutions are considerably easier to install. For this reason, recirculation is generally preferred for smaller apartments, kitchens and refurbished properties.