What this video covers
The extractor fan mistake in this clip is one almost everyone makes, and it is about timing rather than the fan itself.
Switching the fan off as you leave the bathroom stops it at exactly the moment it still has work to do. The air is saturated, every surface is wet, and clearing that takes roughly half an hour of continued extraction.
The takeaway
Leave the fan running for about 30 minutes after you finish. If your switch does not allow that, a timer or humidity-sensing fan does it for you and removes the decision entirely.
Read the full written guide: How to Remove Mold from a Bathroom Ceiling.