Symptoms
- Fan noise louder than when new
- Noise increases at certain times of day
- Rattling or buzzing in addition to fan noise
- Noise changes when moved to a different spot
Likely causes
- CommonFilter clogged with dust, pet hair, or debrisA dirty filter makes the fan work harder and louder to pull the same amount of air through.
- CommonAuto mode increasing fan speed due to detected particles or odorsSmart/auto sensors ramp the fan up when air quality readings are poor, which is normal behavior.
- PossibleUnit placed too close to a wall or in a cornerRestricted air intake or exhaust can increase noise as the fan compensates.
- PossibleDebris caught in the fan bladeA stray hair, string, or dust clump can cause a rattling noise as the fan spins.
- Less commonWorn fan motor bearingsProduces a grinding or whining noise that worsens over time.
What to do
- Check the filter replacement indicator or count of months in use, and replace the filter if it's overdue or visibly gray and clogged.
- Switch the unit out of auto mode temporarily to a fixed lower speed to see if the noise level matches that setting.
- Move the unit at least a foot away from walls and furniture to give it clear intake and exhaust space.
- Unplug the unit and check the fan blade area (behind the filter) for hair, string, or debris caught in it.
- Vacuum the intake grille and any visible dust buildup on the housing.
- If a persistent whine or grinding continues at a fixed low speed with a clean filter and clear surroundings, the fan motor may be wearing out.
Tools and parts
- Vacuum with brush attachment
- Soft brush
Replacement air purifier HEPA filterSearch: “air purifier replacement filter for [brand/model]”
When to call a pro
Consider replacement rather than repair if the fan motor itself is worn, since that's rarely cost-effective to fix on a consumer air purifier.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.