Range hood not extracting well
Not urgent Weak extraction is a comfort and grease-buildup issue rather than an emergency, though a hood that has become noisy or smells hot should be switched off until it is looked at.
What this symptom might mean
A hood that runs but does not clear the air usually has a restriction somewhere between the filter and the outside. Grease filters that have not been washed in months choke the intake; Whirlpool's guidance is simply that they should be cleaned often. On a recirculating (ductless) hood, the charcoal filter saturates and needs replacing roughly every six months, and a recirculating hood will never move steam out of the kitchen, only trap grease and some odour. On a ducted hood, the duct can be crushed, undersized, run in ridged flex that Broan says creates turbulence, or blocked at the roof or wall cap; Bosch's advice is to check the ducts for blockage, damage or a disconnected joint.
Two things outside the hood also matter. A tightly sealed newer home may not let enough air in to replace what the hood pushes out, so the fan labours and the damper barely opens; Whirlpool notes some installations require make-up air. And a hood mounted too high above the cooktop, or with cabinets closer than the minimum clearance, simply misses the plume. If all that is in order and airflow is still weak, the fan motor may be slowing, the blower wheel may be caked with grease, or a speed control may have failed.
Safe checks you can do first
- Wash the grease filters. Pull the metal mesh or baffle filters and wash them in hot soapy water or the dishwasher if the manual allows. If they are bent or the mesh is clogged beyond cleaning, replace them.
- Charcoal filter. If the hood recirculates, find the charcoal filter behind the grease filters and replace it if it is more than six months old or smells of old grease. Charcoal filters cannot be washed.
- Damper and outside cap. Run the hood on high and check the outside cap (wall or roof) opens and blows. If it does not move, the duct or cap is blocked; birds and lint are common finds. Do not go on the roof.
- Duct behind the hood. If you can see the duct above the hood or in the cabinet, look for crushed, ridged or disconnected sections. Note the diameter; a hood specified for a 150 mm (6 in) duct on 100 mm (4 in) dryer duct will never perform.
- Make-up air. Open a nearby window a crack and run the hood again. If extraction improves noticeably, the house is too tight for the fan and needs a make-up-air solution from an HVAC contractor.
- Use. Start the hood a few minutes before cooking and leave it running a few minutes after; use the rear burners under the deepest part of the hood.
- Controls. Check the fan is set to a high speed and that any auto or timer mode has not dropped it to low.
Nothing above involves gas, wiring, refrigerant or removing panels. Those are technician-only: Removing the blower assembly or motor; Electrical work on the hood's wiring or switch; Roof work and duct alteration inside walls or attic.
Repairs a technician may recommend
After inspection, not from the symptom alone.
- Blower wheel cleaning or replacement. When the wheel is caked with grease and out of balance, or a blade is broken.
- Fan motor replacement. When the motor is slow, noisy or hot, with clean filters and a clear duct.
- Speed control or switch replacement. When only some speeds work or the fan runs at one speed regardless of setting.
- Damper replacement. When the backdraft damper at the hood or the cap is stuck, broken or missing.
- Duct repair or replacement. When the duct is crushed, disconnected, undersized or run in flex. Ductwork beyond the hood connection is often an HVAC or renovation job, and the finding says which.
- Hood replacement or re-mounting advice. When the hood is simply too small, too high or the wrong type for the cooktop; we say so rather than sell a repair.
When to book
Book when the filters are clean, the outside cap opens, and the hood still does not clear the air; when the fan has become noisy, slow or hot; when only some speeds work; or when the damper appears stuck. Tell us whether the hood is ducted or recirculating, the make and model, and whether it is an over-the-range microwave with a built-in fan, since the latter is serviced as a microwave. The diagnostic is $89 and waived when you proceed with the repair. See range hood repair; if a new hood or duct run is the answer, range, cooktop and wall-oven installation covers what we can and cannot do on the ducting side.
Questions
My hood is loud but doesn't move much air. Why?
Noise without airflow usually means the fan is pushing against a restriction: clogged filters, a crushed or undersized duct, or a stuck damper. Check the filters and the outside cap first.
Can a recirculating hood be converted to vent outside?
Many can, if a duct route to the outside exists and the hood has a ducted option. The duct run itself is usually a renovation or HVAC job; we can advise on what the hood supports.
What size duct does a range hood need?
Broan's guidance is metal duct only, smooth rather than ridged, and never below the size the hood specifies; a common minimum is 150 mm (6 in) round or its rectangular equivalent, with larger hoods needing more.
Does a hood need make-up air in Ottawa or Gatineau?
Newer, tightly built homes and high-capacity hoods can need it; the symptom is a hood that struggles until a window is opened. Your municipality's building rules set the threshold, and an HVAC contractor designs the solution to suit your local building, electrical and gas codes.
Related
Sources
- Bosch: Ventilation hood not extracting
- Whirlpool Product Help: Vent hood not removing smoke or odor
- Broan-NuTone: What type of duct is best for venting a range hood?
Reviewed 2026-09-24.
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