Updated
Cooker Hood Not Clearing Steam
The hood runs but the kitchen still fills with steam, the windows stream and the smell of cooking hangs around.
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What's happening?
There are two kinds of cooker hood and they do completely different jobs. A ducted hood pushes air out of the building. A recirculating hood passes air through a grease filter and a carbon filter and puts it straight back into the room — it takes some odour out and no moisture at all. Approved Document F is explicit on this: a recirculating cooker hood on its own does not provide ventilation that complies with Part F. The required intermittent extract rate for a kitchen is 30 litres per second where a cooker hood extracts to the outside, and 60 litres per second where there is no hood or the hood does not extract outside. So a hood that runs loudly and clears nothing is very often working exactly as built — it just was never ducted.
What usually causes it?
- The hood is a recirculating unit and was never ducted to outside, so it removes no moisture at all
- Ducting fitted but never connected through to an external vent, or terminating in a void or a cupboard
- A long, kinked or flexible duct run choking the airflow well below the rated extract rate
- The external grille flap painted shut, blocked by debris or covered by a bird guard that has clogged
- Grease filters saturated and never washed or replaced
- The carbon filter in a recirculating hood exhausted, so odour is no longer removed either
- The hood too small for the hob or mounted too high above it to capture the plume
Is it dangerous?
The steam itself is not, but a kitchen that never clears its moisture is the reason condensation and mould appear on the cold walls, in the corners and behind the units — and GOV.UK guidance on damp and mould sets out the health risks that follow. A grease-laden filter above a hob is also a fire risk, which is why filter cleaning is a manufacturer instruction rather than a suggestion.
Can I fix it myself?
Establish which kind of hood you have: look on top of the unit for a duct going into the wall or ceiling, or for a carbon filter cartridge inside. Wash or replace the grease filters — most are dishwasher-safe — and replace the carbon filter if there is one. Go outside and check the external grille actually opens when the hood runs. Where the duct is flexible and coiled behind the unit, straightening and shortening it makes a real difference to what it moves.
When should you call a kitchen fitter?
Call a kitchen fitter to duct a recirculating hood to outside, to re-run choked or disconnected ducting, or when a new hood is going in as part of kitchen work. The extract route is designed at the same time as the units, because the run and the core drilling have to be planned before the cupboards go on the wall.
What will the kitchen fitter actually do?
- Establish whether the hood is ducted or recirculating and what the duct actually connects to
- Check the duct run for length, kinks, crushed flexible sections and dead terminations
- Plan and install a rigid duct route to an external terminal with a working grille
- Fit a hood sized to span the hob and set it at the height the manufacturer specifies above it
- Confirm the installation meets the kitchen extract rate required by the Building Regulations
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