The exhaust fan — that rattling, dusty vent hanging above the toilet — is the single most important gadget for the health of a bathroom. It eliminates the steam from a hot shower, helping battle the mould and mildew constantly threatening a bathroom’s finishes. The device also helps fix more immediate air quality issues — they’d never say it in front of a client, but in the salty slang of a plumbing supply house, pros refer to it as a fart fan.