Kitchen extract removes steam, odour and grease at the hob or the cookline. Comfort air conditioning treats the people in the room. They are different systems. Do not dump kitchen grease into a comfort cassette or a wall split and call it ventilation. Grease blinds filters, coats coils and becomes a fire and hygiene problem. A home kitchen diner can still have a split, provided the hob has a proper extract and the indoor unit is placed out of the grease plume. A commercial kitchen needs a kitchen ventilation design, not a bigger fascia.
A fryer plume aimed at a ceiling cassette
The extract captures at source, with a canopy or a domestic hood ducted outside, and replacement air has to enter from somewhere lawful. Comfort cooling recirculates room air across a coil to remove heat. If the only path for cooking effluent is the split's return grille, the coil becomes the filter for the fryer. That mistake shows up as sour smells, water leaks from a blocked tray, and a unit that no longer meets its cooling duty. Cleaning a user filter will not undo a grease-loaded coil. A maintenance visit might. Preventing the path is cheaper.
A home kitchen diner with a ducted hood
A wall unit or a cassette can serve a UK kitchen diner if the survey places it so the return is not inside the hood's failure zone, and if a real extract already leaves the building. Cooking load still belongs in the cooling calculation. A Sunday roast plus south-facing glass is why a nominal 3.5 kW guess fails. Condensate will be heavier on humid cooking days. Gravity fall or a pump has to be real. The refrigerant side is an F-gas install. GOV.UK publishes certification for companies that open that circuit. The extract fan is not an F-gas job, but it still needs a competent electrical supply and a route that does not blow into a neighbour's window. Energy Saving Trust's air-to-air pages describe the comfort split, not the hood.
A cafe cassette asked to cover the cookline
Cafes and shop serveries often ask for one ceiling cassette to do the kitchen, the queue and the till. The cassette can cool the customer side. The cookline still needs extract sized for grease and steam, with make-up air that does not extinguish the cooling. Building control and your kitchen designer own that ventilation rate. This page will not invent one. Staff comfort remains an HSE topic: reasonable temperature for the work, with radiant heat from ovens called out honestly. A comfort unit cannot cancel an open chargrill. Spot cooling for a pass may be possible. It is a surveyed extra, not a mode on the remote.
- Extract at the hob, ducted as the kitchen design requires.
- Comfort cooling for the occupied zone, away from the plume.
- Make-up air is part of the extract design, not an open window by luck.
Two contracts: hood and comfort coil
Say what you cook, whether the hood is ducted, where replacement air comes from, and which zone is for people rather than for the range. Ask the air conditioning quote to exclude kitchen extract or to name a ventilation partner. One company pretending to cover both without a drawing is how grease meets the coil. Service both. Filters on the comfort unit, and the canopy on its own contract. If the comfort system is large enough to cross the GOV.UK inspection threshold, that inspection is additional to the deep clean of the hood.
Stop treating the cassette as the kitchen extract
Stop if the proposal points a cassette at the hob instead of fitting extract. Comfort cooling recirculates air. Grease and steam need a dedicated extract to outside. A finer filter clogs faster and still does not replace extract. Keep grease out of the comfort unit. Clean or replace the comfort filter as a separate habit. The extract installer needs F-gas certification only if they also open a refrigerant circuit. Kitchen extract is ventilation. The split or cassette beside it needs a certified company for the refrigeration work.
Frequently asked questions
Will a better filter grade make grease acceptable?
A finer filter clogs faster and still does not replace extract. Keep grease out of the comfort unit. Clean or replace the comfort filter as a separate habit.
Does the extract installer need F-gas certification?
Only if they also open a refrigerant circuit. Kitchen extract is ventilation. The split or cassette beside it needs an F-gas certified company for the refrigeration work.
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How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.