How to clean or replace the bathroom exhaust fan
To clean a bathroom exhaust fan, turn off the breaker, take down the grille, wash it and vacuum the housing and blades. Then hold a tissue to the running fan: it should stay against the grille. If the motor is noisy, hot or caked in dust, replace it with a matching part. The duct must end outdoors.
How often to clean a bathroom exhaust fan
Federal guides don't give a fixed cleaning interval. The Building America Solution Center, run by a U.S. national lab, says that vacuuming the cover and blades restores suction, so let the fan's performance guide you.
| Check | When |
|---|---|
| Vacuum the grille | Whenever you see dust on it |
| Open it up, clean the housing and blades | Once a year is a sensible habit, and right after you move in |
| Tissue test for suction | Each time you clean it |
| Look at the outdoor vent cap | Once a year, from the ground if you can |
How long to run it is a separate question, and sources differ. The Department of Energy says to turn exhaust fans off within 20 minutes unless they're built for continuous use. The Building America guide says about an hour after a shower helps control humidity. If your mirror and walls stay wet at 20 minutes, go longer. A timer switch handles this for you.
What you need to clean or replace a bathroom exhaust fan
- A stable step stool
- A vacuum with a brush attachment
- Screwdriver, dust mask and safety glasses
- Warm soapy water for the plastic grille
- A phone camera for the label inside the housing
- A tissue or a square of toilet paper for the suction test
If you're replacing parts, the model number on the label inside the housing is what you'll search for. Buy the motor assembly listed for that exact model, not a close match.
If you're replacing the whole fan, these numbers help:
| Spec | Guide figure |
|---|---|
| Minimum airflow, switched on and off by you | 50 cfm, and ENERGY STAR suggests at least 70 cfm to allow for duct losses |
| Minimum airflow, runs continuously | 20 cfm, and ENERGY STAR suggests more than 50 cfm |
| Noise, intermittent use | 3 sones or less |
| Noise, continuous use | 1 sone or less |
How to clean a bathroom exhaust fan, step by step
- Kill the power
Switch off the breaker for the bathroom, then flip the fan switch to confirm nothing runs.
- Lower the grille
Pull it down gently and squeeze the two spring clips to release it. Wash it and let it dry.
- Vacuum the inside
Clean the housing, blades and motor with the brush attachment. Don't get water on any electrical part.
- Read the label
Photograph the model number while you're in there, so you can find parts later.
- Inspect the motor
Spin the blades by hand. They should turn freely. Stiff blades or thick caked dust that won't lift means it's time to replace the motor.
- Refit and test
Reinstall the grille, restore power and hold a tissue to the grille with the fan on. It should stay there.
- Trace the duct
Find the outdoor cap and confirm the damper opens with the fan running, and that nothing blocks it.
Bathroom fan warning signs
- The tissue drops off the running fan. Clean it, and if the result is the same, look for a blocked duct or a worn-out motor.
- The housing smells hot, or the fan squeals, grinds or runs slowly. Stop using it until you've checked it.
- Mold or peeling paint on the ceiling. EPA says to bring in a pro for areas over about 10 square feet.
- A duct that ends in the attic, crawl space or soffit. The model code doesn't allow it, and the moisture stays in the house.
- Smoke or flames from the housing. Turn the breaker off and call 911.
- A combined fan, heater and light. Check it for recalls. In 2012 CPSC recalled about 68,000 Harbor Breeze units after 11 reports of overheating with smoke or flames in the housing.
Replace a bathroom exhaust fan yourself or call a pro?
Cleaning is DIY. So is a plug-in motor swap if your unit's motor connects to a socket inside the housing and the breaker is off. If you see wires tied to the house wiring with connectors, or anything scorched, call a licensed electrician. Adding a new circuit, timer or switch is also electrician work in most places, and may need a permit.
Finding where the duct goes takes a look in the attic. If that's a tight space, or if the insulation looks old and loose, leave it to a pro. Some older loose-fill insulation can contain asbestos, so don't disturb it.
A good duct job keeps the first three feet straight, uses few bends, seals the joints and has a cap with a damper. If yours falls short, an HVAC contractor or electrician can correct it, often while replacing the fan.
How long to run a bathroom fan and other questions
How long should a bathroom fan run after a shower?
The Department of Energy says to turn exhaust fans off within 20 minutes, while the Building America Solution Center says about an hour helps control humidity. Run it until the mirror and walls are clear, and use a timer if you forget.
Can a bathroom fan vent into the attic?
No. The model residential code says exhaust air can't go into an attic, soffit, ridge vent or crawl space. It must be discharged outdoors, so ask a contractor to fix a duct that ends indoors.
How do I test whether my bathroom fan works?
Turn it on and hold a tissue against the grille. If the fan has enough suction to hold it there, it's moving air.
Sources: basc.pnnl.gov, seattle.gov, U.S. Department of Energy, CPSC, EPA
General guidance for U.S. homes, not professional advice. For gas, electrical and structural work, call a licensed pro.