Extraction symptoms
When the ductis the problem.
The hood runs loudly and the smell stays. That is where you start at the duct.
01
It runs and the smell stays
If the noise is strong but the air above the hob is not moving, the duct is either packed with grease, its outside termination is shut, or the hood was never ducted at all and is recirculating the air.
02
Steam gathering on the ceiling
Steam rising past the hood and collecting on the ceiling and the cupboards means the pull is weaker than the steam being produced. Usually the route is long, or it carries too many bends eating into the draw.
03
Grease dripping from the duct
Greasy drops coming off the joint above the hood mean grease has built up inside the duct, cooled and started to run back. That case needs the route cleaned, not just a new filter.
04
Outside air blows back in
Feeling hot air or dust coming in through the hood while it is off means the flap on the outside termination is broken or missing. That opening needs a flap that lifts with the extraction and falls shut after it.
In short
The duct work.
Service
Kitchen flue and duct installation
Included
The duct route, joints, outside termination and its flap
Where it applies
Home and flat kitchens, and restaurant and shop kitchens
Harder cases
Flats with no outside wall, and long routes with bends
Hours
Daily, 6:00 in the morning to 12:00 midnight
How we route it
From the hood tothe outside wall.
The route is decided before a single component is bought.
We find the nearest way out
We work out the shortest route from the hood to the nearest outside wall or light well, because every extra length and every bend takes from the pull.
We size the duct
The duct is sized against the hood and the route. Narrowing it so it can pass behind a cupboard kills the draw, however strong the hood is.
We run it and seal the joints
The duct runs with as few bends as possible, and every joint is sealed so no steam or smell escapes into a false ceiling or behind the cupboards.
We fit the flap and test
The outside opening takes a flap that lifts with the extraction and closes after it, then the hood runs and we confirm the air above the hob really is moving.
The detail
Every bend eatsinto the pull.
A hood does not pull air so much as push it along the route behind it. The fan produces a fixed amount of force, and the duct spends that force in proportion to its length, the number of bends and how narrow it is. Which is why a powerful hood on a poor duct performs worse than an ordinary hood on a short straight run.
A sharp bend costs more than length. Air passes along a long straight run with reasonable resistance, but every right angle breaks its movement and cuts the flow noticeably. So when we plan a route we would rather add a little length than add another bend.
Grease is the long term problem. Steam from cooking carries fine grease with it, and that cools against the duct wall and sticks. Over time it becomes a layer that narrows the bore and raises the resistance, so the pull weakens gradually. The hood filter catches part of it, which is why cleaning that filter regularly extends the life of the whole route.
A restaurant kitchen is a different case entirely. The volume of grease and steam is far higher, so the run needs a wider bore and a grease trap ahead of the fan to stop grease collecting inside the duct itself. Access openings along the route are part of the design rather than an afterthought, because a restaurant duct with no access cannot be cleaned without breaking into it.
External links for referenceMinistry of Electricity and Water (the public water network in Kuwait)
Questions
Asked aboutkitchen ducts.
The noise comes from the fan and the extraction comes from the route, and they are not the same thing. Usually the duct is blocked with grease, its outside opening is shut, or the hood was never ducted and is simply passing air through a filter back into the kitchen.
We look for the nearest outside wall or light well we can reach. If none is possible, the only option is a hood running on a filter that returns the air to the kitchen. That reduces grease but removes neither steam nor heat, and you should know that difference before choosing.
Yes, and length, bends and bore all matter. Every extra length and every right angle spends part of the fan's force, and a narrow bore is the worst of the three. So we plan the route before buying instead of trying to compensate with a stronger hood afterwards.
Yes. A restaurant kitchen needs a wider bore, a grease trap and access openings along the route, because the volume of grease is far greater than at home. Tell us the type of kitchen and how many cooking points it has so we arrive with the right picture.
It means the layer inside the duct has built up enough to run back down under gravity. Cleaning the filter alone will not help here, because the grease is inside the route itself. That needs the run opened and cleaned, and sometimes an access opening added where there was none.