Bathroom mould removal before and after treatment. Multi level apartment with poor bathroom ventilation. To make matters worse the window is non functional allowing light but not air inside. This is a common problem in multi level apartments as the builder has only a couple of options to choose from for ventilation. The method used in this case for the exhaust fan system was satisfactory however the fan itself was under powered. In this case the exhaust fan was upgraded to a more powerful unit and the ceiling will be painted using a mould inhibitor additive or wet area paint with a min of two coats.