Room by Room
Extraction is the part of a kitchen nobody looks at until it smells
A cooker hood is a fan, a duct and a route out of the building, and the fan is the least important of the three. Most disappointing extraction is a ducting problem.
Comparisons of kitchen extraction usually pick a winner. This one picks the circumstances, which is more useful.
The difference in one place
- Grease and water vapour, not smoke, are the bulk of what extraction removes.
- Duct diameter, length and bends matter more than the airflow figure on the box.
- A recirculating hood can address odour but leaves heat and moisture in the room.
What extraction is actually for
Frying and boiling release grease aerosol and a large volume of water vapour, and both travel further through a house than the smell does. The moisture is the part people underestimate, because it migrates to the coldest surface in the building and condenses there rather than in the kitchen.
Cooking odour is absorbed by soft furnishings, which is why an open-plan kitchen leaves the sofa smelling faintly of whatever was cooked the night before. Fuel-burning appliances also release combustion products indoors, which is a safety question rather than a comfort one and belongs to a qualified installer under local rules. A quiet hood that actually gets switched on removes far more of all this than a powerful one that the cook finds unpleasant to stand beside.
Ducted and recirculating hoods are different machines
A ducted hood carries air out of the building, taking heat, grease, odour and water vapour with it in a single movement. A recirculating hood passes air through a carbon filter and returns it to the room, which can reduce odour but does nothing about humidity or heat.
The quieter point is that carbon filters saturate and stop working long before they look used, and a hood with an exhausted filter is an expensive light fitting that makes noise. Recirculation is often the only option in a flat where the external wall cannot be penetrated, and it is a fair compromise if filters are genuinely replaced. Where humidity has nowhere to go, a separate extract fan or a whole-house ventilation system has to carry the load the hood was never taking.
The duct decides the performance
Air moving through a duct loses energy to friction, and every bend, every reduction in diameter and every metre of hose costs airflow the fan cannot recover. Flexible corrugated ducting is convenient to fit and is among the worst choices, because the ridged interior generates turbulence along its entire length. Smooth rigid duct at the largest diameter the appliance permits, with few and gentle bends, is usually what separates a hood that works from one that does not.
Room to room, reducing a duct to suit a smaller hole in the wall throttles the whole system regardless of what the fan is capable of moving. The external termination matters as much, because a fine mesh grille slowly clogs with grease and strangles a system that performed well when it was new.
Noise is why extractors get switched off
Most of the sound from a hood is air noise rather than motor noise, generated wherever air accelerates through filters, gaps and tight turns. A larger hood running on a low setting moves the same volume of air far more quietly than a small one running at full speed. Remote motors, mounted in a loft or on an outside wall, put the noisiest component away from the person standing at the hob, and they need proper installation.
An extractor that is uncomfortable to stand under gets turned on late and turned off early, which is precisely when the grease reaches the ceiling.
Running the fan on for a while after cooking clears the residual moisture, and that is the first habit people abandon when the machine is loud.
Where it sits over the hob
A hood captures a plume that is already rising, so it needs to cover the cooking area rather than sit neatly centred on the run of cabinets. Mounted too high it loses the plume to room air currents, and mounted too low it becomes a hazard over a pan and something to hit your head on.
Manufacturers state a mounting height range for their own product, and that instruction takes precedence over any general rule someone repeats online. An island hood has no wall behind it to help contain the rising plume, which is why extraction over an island generally needs more capacity than the same hob against a wall. A door or window near the hob sets up a cross draught that pushes the plume sideways before the hood has any chance of catching it.
Maintenance is most of the story
Grease filters exist to keep the fan clean, and a clogged metal filter both restricts airflow and becomes a fire risk directly above a flame. Metal mesh filters can be washed and most tolerate a dishwasher, which is the practical reason they get cleaned when paper and carbon ones do not. Grease that gets past the filter coats the impeller and the inside of the ductwork, where it is hard to reach and permanently reduces what the machine can move.
A hood that has never been cleaned rarely returns to its original airflow, because the deposit hardens into a varnish that no longer wipes away. In a well-sealed home, pulling air out without providing a route for replacement air simply starves the fan, and where fuel-burning appliances are present that becomes a matter for a qualified professional.
Side by side
| Consideration | What it means in practice |
|---|---|
| What extraction is actually for | Grease and water vapour, not smoke, are the bulk of what extraction removes. |
| Ducted and recirculating hoods are different machines | Duct diameter, length and bends matter more than the airflow figure on the box. |
| The duct decides the performance | A recirculating hood can address odour but leaves heat and moisture in the room. |
The takeaway
Spend the effort on the duct, size the hood generously, run it slowly and wash the filters.
Buy slowly. The gaps are not a problem.
Questions readers ask
Is a recirculating hood worth having at all?
It can handle odour and grease if the filters are replaced on schedule, but it returns heat and moisture to the room. In a flat with no external route it is better than nothing, ideally paired with a separate extract fan for humidity.
Why is my extractor loud but not effective?
Almost always restricted ducting. Flexible hose, a reduced diameter or sharp bends make the fan work against resistance, and that energy comes out as noise instead of airflow.
