💧 Water & Weather
Bathroom Extractor Fans: Why They Matter and How to Check Yours
A weak or noisy fan is a common cause of mould. Here is how to test, clean, and choose a replacement.
Dana Whitlock · Sep 8, 2026 · 5 min read · 4 steps
A shower can release a large amount of moisture into a small room in minutes. Without a working extractor fan, that moisture settles on cold walls and ceilings and feeds mould.
Many fans are fitted, forgotten, and slowly clog with dust until they barely move any air.
Test it
Turn the fan on and hold a single sheet of toilet paper near the grille. A working fan should hold it against the cover. If the paper barely moves, the fan or its duct is blocked, or the fan is too weak for the room.
Clean it
Switch off the power at the fuse box. Remove the cover — most clip or unscrew off — and wash it in warm soapy water. Vacuum and wipe dust from the blades and housing. If you can, check the outside vent is not blocked by debris or a stuck flap.
Use it well
Run the fan during showers and for at least 15–20 minutes afterwards, and keep the door closed so moisture goes out rather than into the rest of the home. Fans with a humidity sensor or overrun timer do this automatically.
Choosing a replacement
Look at the extraction rate (in litres per second or cubic metres per hour) compared with the room size, and the noise rating. Quiet fans are more likely to be left on. Wiring a fan into the lighting circuit is a job for a qualified electrician.
This is general home-maintenance information, not professional advice. Building codes, permits, and safe practices vary by location — consult a licensed contractor, electrician, or plumber for work beyond your experience.