I have a friend who recently bought a house with a downstairs toilet that has no external walls - it is basically off the hallway and on the shared wall of a semi-detached house. At the moment there is no ventilation and we were trying to figure out the best way to achieve this. Any ducting would have to be at least 6-8 metres and would not be easy to install. Is there such a thing as an "extractor" fan that doesn't need a vent, e.g. with washable filters like in some kitchens? Any other suggestions?