How often should you clean a bathroom exhaust fan?

Short answer

Clean the bathroom exhaust fans every 6 to 12 months. The fan's job is to pull steam out of the room before it settles on the walls, and it can't do that through a grille packed with dust. Taking the grille down, vacuuming it and the fan blades, and putting it back takes 15 to 30 minutes per fan and costs $0 to $5.

Why it matters

A hot shower puts a surprising amount of water into the air. The exhaust fan carries it outside. When it works, the mirror clears in a few minutes and the walls dry. When it doesn't, the moisture condenses on the coolest surfaces, usually the ceiling and the corners above the shower, and that's where the black spots of mold start. Paint peels, the drywall softens, and in a bad case the ceiling joists above take on water.

The fan loses its pull slowly. Dust from the room gets drawn onto the grille and stays there, and the lint that gets through coats the blades. A blade with a layer of fuzz on it is heavier, out of balance, and moves less air for every turn. The motor works harder against the load, runs hotter, and burns out years early. A fan motor isn't an expensive part, but replacing one means working in the ceiling. A vacuum twice a year is a better deal.

When to do it more often

The fan doesn't care about the season, only about how much it runs and how dusty the room is. A bathroom used by several people every morning loads its fan faster than a guest bath that sees a shower a week. A fan that also serves a laundry area, where lint hangs in the air, deserves a look every few months. And a fan that's visibly fuzzy when you glance up at it is overdue whatever the calendar says.

What you need

A step ladder
A vacuum with a brush attachment
A screwdriver, for the few grilles that are screwed rather than clipped

Steps at a glance

Turn off the fan at the switch and, for safety, at the breaker.
Pull the grille down and squeeze the spring clips on each side to free it.
Wash the grille in warm soapy water, or vacuum it if it's only dusty, and let it dry.
Vacuum the fan blades and the housing with the brush attachment, turning the blades by hand to reach every one.
Wipe the blades with a damp cloth if fuzz is stuck on.
Clip the dry grille back in and restore power.

You're done when the fan runs quietly and a square of toilet paper held to the grille is pulled against it and stays there.

Signs it's overdue

Dust caked on the grille, often in a gray ring around the opening.
The fan is louder than it used to be, or rattles, from blades thrown out of balance.
The mirror stays fogged long after a shower, because the fan isn't moving enough air.

DIY or pro

This is an easy job for anyone comfortable on a step ladder. The grille comes down by hand on nearly every fan, and the vacuum does the rest. Nobody sells fan cleaning as a service, so there's no price to compare.

Where a pro comes in is when the cleaning doesn't bring the fan back. A fan that still won't hold the paper square after cleaning may have a dead motor, a crushed duct above the ceiling, or a duct that ends in the attic instead of outside. Those are repairs, and the last one is worth fixing because it dumps shower steam onto your insulation.

Safety

Electricity: switch the fan off and flip its breaker before you reach into the housing. The motor and its wiring sit right where you'll be working, and a fan that starts with your fingers on the blades can hurt you. Don't spray water into the housing.

FAQ

How do I know if my bathroom fan is working?

Hold a square of toilet paper up to the grille with the fan on. If it sticks, the fan is pulling air. If it drops, the fan needs cleaning or the duct is blocked.

Can I wash the bathroom fan grille?

Yes. Warm soapy water and a brush clean it well. Let it dry fully before it goes back up.

Why is my bathroom fan so loud?

Dust on the blades throws them out of balance, and the fan rattles. Cleaning usually quiets it. If it stays loud, the motor bearings are wearing out.

How long should the fan run after a shower?

Long enough to clear the mirror and dry the walls. A fan on a timer switch that runs after you leave does this without anyone remembering.