Symptoms
- Smoke and cooking smells linger despite the fan running
- Fan seems to run at full speed with weak suction
- Steam and grease accumulate on nearby cabinets
- Recently noticed the hood seems less effective than before
Likely causes
- CommonClogged or crushed exterior ductGrease and debris build up inside duct runs over years, or a duct can get crushed during other work in the wall or ceiling.
- CommonDuctless (recirculating) hood with an old charcoal filterCharcoal filters need regular replacement, and an old one can no longer absorb odors even if the fan runs fine.
- PossibleBackdraft damper stuck closedThe flap that lets air out but blocks outside air from coming in can stick shut from grease buildup.
- PossibleUndersized or overly long duct runA duct that's too long, too narrow, or has too many bends reduces airflow regardless of fan power.
What to do
- Determine if your hood vents outside (ducted) or recirculates air (ductless), since the fix differs.
- For ductless hoods, replace the charcoal filter, which typically needs changing every 6–12 months depending on use.
- For ducted hoods, clean the grease filter and check the exterior vent cap outside for obstructions like debris, insects, or a stuck damper.
- If accessible, check duct runs for crushed sections, especially near recent renovation work.
- Confirm the backdraft damper near the fan outlet opens freely by hand when the unit isn't running.
- Consider whether the duct length and number of bends match the manufacturer's specifications if venting issues persist despite clean filters.
Tools and parts
- Screwdriver
- Flashlight
Range hood charcoal filterSearch: “range hood ductless charcoal odor filter”
When to call a pro
Call an HVAC or appliance professional if the ductwork itself needs inspection or repair, since that may require accessing walls or the roof.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.