Who designs a commercial kitchen extract scheme
Three competences sit behind a workable extract scheme. A submission signed only by the kitchen equipment supplier is the usual reason a change of use fails on odour.
A commercial kitchen extraction and odour control scheme needs three different competences and they are rarely found in one person. A ventilation engineer sizes the system and designs the ductwork. An air quality specialist justifies the abatement selection and, where the case is difficult, models the dispersion from the discharge point. An acoustician deals with the noise from the fan and the condensers. The environmental health officer reading your submission will look for all three, and a scheme signed only by the kitchen equipment supplier is the commonest reason a change of use is refused on odour.
That is the answer to the question. The rest is about who does which part, and what each has to produce.
What the environmental health officer is assessing
Four things, and it helps to keep them separate in your own head because they are mitigated differently.
Whether the extract rate is adequate for the cooking proposed, which is a matter of canopy design and air volumes. Whether the abatement is proportionate to the odour risk, which depends on what is being cooked, how much, and how close the nearest residential windows are. Whether the discharge point disperses what remains rather than delivering it to a neighbour's bedroom. And whether the fan, the ductwork and the refrigeration plant will be audible above the background at those windows at night.
The officer is working to established guidance rather than to a statutory standard. The reference most authorities use for commercial kitchen exhaust is the Defra guidance on the control of odour and noise from commercial kitchen exhaust systems, which sets out a risk-based approach: assess the odour risk from the cooking type, the kitchen size and the proximity of receptors, then match the level of abatement to that risk. Alongside it sits the industry specification for kitchen ventilation systems used by mechanical contractors, and the British standard series on ventilation for commercial kitchens.
Ventilation engineer or odour specialist
The division of work looks like this.
The ventilation engineer establishes the extract volume from the cooking appliances and the canopy type, sizes the ductwork and the fan, sets the system pressure, designs the make-up air so the kitchen is not in excessive negative pressure, specifies the grease filtration, and produces the schematic and the plant schedule. They also deal with the interlocks that shut off gas if extraction fails, which is a safety requirement rather than a planning one but appears in the same drawings.
The air quality specialist takes that system and answers the planning question: will odour be perceptible at the nearest sensitive receptor, and is the proposed abatement sufficient. Where the risk is high, they will carry out an assessment using the recognised odour methodology and, on a difficult site, dispersion modelling.
Most small schemes do not need both. A single-unit cafe with a domestic-scale hob and no deep frying can be dealt with by a competent mechanical designer and a well-written statement. A restaurant with a charcoal grill in a building with flats above needs the specialist, and pretending otherwise wastes the determination period.
A Ventilation and Extraction Statement is the document that pulls the two together for the planning file. PlanScope drafts it from the answers you give about the unit, the cooking and the surroundings, and flags the air volumes, filter specifications and receptor distances that the designer has to supply.
Choosing the abatement, and who justifies it
Abatement is usually described in three tiers and the specification follows the risk:
- Grease filtration alone, meaning baffle or cartridge filters in the canopy. Suitable only for low odour cooking with a good discharge point and distant receptors.
- Grease filtration plus carbon adsorption, with pre-filtration to protect the carbon. The workhorse solution for most restaurants.
- Grease filtration plus electrostatic precipitation plus carbon, sometimes with ultraviolet or ozone treatment. Used for high odour cooking, tandoors, charcoal, heavy frying, or where the discharge point is compromised.
The choice has to be justified rather than asserted, and the justification belongs to whoever is accountable for the odour conclusion. Three things make it credible: the carbon residence time or bed depth stated as a figure, the filter efficiency claimed with the manufacturer's data behind it, and a maintenance interval tied to the hours of cooking rather than to a calendar.
Carbon is where schemes fail in operation. Carbon has a finite capacity, and an operator who changes it when the smell returns has already generated the complaint. Put the replacement interval in the maintenance schedule, offer it as a condition, and keep a log.
An Odour Assessment is a report councils normally expect from a suitably qualified specialist, and professional review before submission is strongly advised. The meaning of competent person across the planning regimes is worth understanding here, because odour is one of the areas where no statutory register exists and the authority is relying on professional judgement and institute membership instead.
The discharge point and dispersion
The discharge point does as much work as the filtration, and it is the item most often compromised by the building.
The guidance position is that extract should discharge vertically at high level, clear of the roof, with the termination at least a metre above the ridge or the highest part of the roof where that is practicable, and at a velocity high enough to carry the plume upwards rather than letting it fall back. Where that cannot be achieved, the answer is more abatement, not a lower flue.
Wall discharges, discharges into a courtyard, and terminations below the eaves of a taller adjacent building are all problems. So is a flue that meets the height requirement but sits within a few metres of an opening window on a neighbouring elevation.
Dispersion modelling is the tool for the hard cases, and it needs a specialist with the software and the meteorological data. It is not needed on most small schemes, and asking for it where the answer is obvious adds weeks. Where the building leaves no good flue route, it is the only way to demonstrate the outcome.
Noise from the plant is a separate discipline
Extract fans, make-up air units and refrigeration condensers produce a broadband hum with tonal content, and the assessment is made against the background sound level at the nearest window using the British standard method for rating industrial and commercial sound. That is an acoustician's work, not a ventilation engineer's.
The mitigation is ordinary: attenuators in the duct, anti-vibration mounts, acoustic enclosures around external plant, a fan selected to run at lower speed with a larger duct, and a limit on operating hours. The design consequence is that attenuators take space and add pressure drop, so the acoustician has to be involved before the duct route is fixed rather than after.
A Noise Impact Assessment covering the plant, and where relevant the customers and deliveries, is the companion document to the extract statement. Submit them together, because an officer reviewing one will ask for the other.
Landlord constraints on the duct route
This is the practical bottleneck on almost every high street unit. The duct has to get from the kitchen to roof level, and the routes are limited.
An internal riser through the upper floors needs the landlord's consent and often the consent of the occupiers above. An external duct on the rear elevation is usually the fallback, and it needs planning permission in its own right on visual grounds, plus listed building consent where the building is listed and careful handling in a conservation area. A duct crossing a party wall engages the party wall procedure. A duct through a neighbouring demise needs a wayleave.
Deal with this before you sign the lease. The commonest expensive mistake in this field is an agreement for lease signed on a unit with no viable flue route, followed by a planning application that cannot be designed around. Ask for the flue route to be identified and consented as a condition of the lease, and get a mechanical engineer to walk the building before exchange.
Briefing the team to avoid a refusal on odour
Give the designers this information at the start and the scheme usually lands first time:
- The menu and the cooking methods, honestly, including any charcoal, tandoor, wok or deep frying.
- The appliance schedule with ratings.
- Hours of operation, including preparation and cleaning.
- A measured survey showing the available duct route and the roof.
- The distance and height of every residential window within about 20 metres, with photographs.
- Any existing planning conditions on the unit and any complaint history.
Then ask for four deliverables: the mechanical schematic and plant schedule, a written odour risk assessment with the abatement justification, an acoustic assessment of the plant, and a maintenance schedule you are content to see turned into a condition. Offer the condition wording yourself.
Where a draft needs review and sign-off before it goes in, the professional directory is the route for that. Enter your postcode on PlanScope to see which documents a restaurant, takeaway or cafe proposal is likely to need.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.
Frequently asked questions
Can my kitchen equipment supplier design the extraction scheme?
They can size the canopy and supply the plant, but a planning submission usually needs more. The abatement justification and the odour conclusion belong to someone accountable for them, and the plant noise assessment is an acoustician's work. A supplier's schematic on its own is the commonest reason an application is refused on odour.
How high does a kitchen flue have to terminate?
Guidance expects a vertical discharge at high level, clear of the roof, with the termination at least a metre above the ridge or highest part of the roof where practicable, at a velocity that carries the plume upwards. Where that cannot be achieved, the answer is more abatement rather than a lower flue.
When is odour dispersion modelling needed?
On difficult sites where the building constrains the flue route, where receptors are close and elevated, or where high odour cooking is proposed and the discharge point is compromised. Most small schemes with a good flue route and modest cooking do not need it, and asking for it unnecessarily adds weeks.
How often does carbon filtration need replacing?
Carbon has a finite adsorption capacity, so the interval depends on cooking hours and load rather than on the calendar. Set it as a stated number of operating hours in the maintenance schedule, offer that schedule as a planning condition, and keep a replacement log. Waiting until the smell returns means the complaint has already happened.
Do I need planning permission for an external duct?
Usually yes, on visual grounds, and separately listed building consent where the building is listed. A duct crossing a party wall engages the party wall procedure and one crossing a neighbouring demise needs a wayleave. Identify and secure the flue route before signing a lease rather than afterwards.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.