Odour assessment for a hot food takeaway
Odour is the ground applicants control most directly on a takeaway application. Here is how the control level is reached, what the filtration train looks like and where discharge points fail.
Most hot food takeaway applications are refused on odour, noise or parking, and odour is the one applicants control most directly. The council wants to see three things: an assessment of how much odour the cooking will produce, a ventilation and filtration system sized to deal with it, and a discharge point high enough and fast enough to disperse what is left.
A hot food takeaway is a sui generis use, so a change from a shop, cafe or restaurant needs planning permission whatever the unit was before. The extraction ductwork usually needs permission in its own right as well, because it alters the external appearance of the building.
What drives the level of odour control needed
The industry approach is a risk assessment rather than a measurement. Four factors set the required level of control.
The type of cooking. Deep frying, chargrilling, tandoor ovens, wok cooking and spit roasting sit at the high odour end. Steaming, boiling, microwaving and reheating pre-prepared food sit at the low end. A menu is evidence, and councils read it.
The scale of the kitchen. Number and rating of cooking appliances, covers served, and hours of operation.
The proximity and sensitivity of receptors. A flat above the unit is the most sensitive receptor there is, followed by dwellings within a short distance, then offices and other commercial uses. Windows, balconies and roof terraces all count.
The dispersion available. A three storey building with a clear roof route and no taller neighbours gives good dispersion. A unit in a courtyard with dwellings on three sides gives almost none.
Combining these gives an odour control level, and the level determines the filtration train rather than the other way round.
The filtration train, in the order the air meets it
| Stage | Purpose |
|---|---|
| Canopy and grease filters | Capture at source, remove grease particulates, protect everything downstream |
| Pre-filters and bag filters | Remove finer particulates before the odour treatment stage |
| Electrostatic precipitator | Removes fine grease aerosol on medium and high risk installations |
| Ultraviolet or ozone treatment | Breaks down odour compounds, used on higher risk installations |
| Activated carbon | Adsorbs the remaining odour compounds, sized by contact time and air volume |
| Discharge | Vertical, at velocity, above the roofline |
Odour neutralising sprays and masking agents are not odour control and should not be presented as the primary system. They change the smell rather than removing the load, and environmental health officers treat a scheme that relies on them as unresolved.
Carbon is the stage that fails in service. Its capacity is finite, it needs replacing on a schedule, and a system with an undersized carbon bed will perform for a few months and then stop working. Give the carbon volume, the design contact time and the replacement interval in the application.
The discharge point
This is where applications are lost.
Discharge should be vertical, at high level, terminating above the roof of the host building and clear of the roofline and openings of neighbouring buildings. Efflux velocity matters as much as height, because a slow plume drops back down the face of the building. Design for a high discharge velocity, typically in the range the published guidance recommends for kitchen extract, and do not fit a cowl or a horizontal bend at the termination that deflects the plume downwards.
Low level discharge into a rear yard, a light well or a side alley is the single most common reason for refusal. So is a termination just below a neighbour's bedroom window.
Where the building is listed or in a conservation area, the duct route becomes a heritage question as well. A stainless steel duct up a principal or visible elevation will be resisted, and the alternatives are an internal riser, a route up a secondary elevation, or a colour-matched duct with a carefully designed termination. Solve this at survey stage, because it can determine whether the unit is viable at all.
Noise comes with it
The extract fan, the make-up air system and the refrigeration condensers all generate noise, and the same neighbours who object to smell object to hum.
Plant noise is normally assessed to the British Standard method for rating industrial and commercial sound, comparing the rating level of the plant with the background sound level at the nearest noise sensitive receptor, measured at the times the plant will run. Late night operation is the difficult case, because background levels fall and the same fan becomes far more noticeable.
A Noise Impact Assessment prepared to that method, with measured background data rather than assumed values, is what an environmental health officer expects. Councils usually expect a suitably qualified author for acoustic work, and professional review is strongly advised.
Attenuators, anti-vibration mounts, acoustic louvres and plant enclosures all work, and all take space. Allow for them in the roof or plant area at design stage rather than adding them after an objection.
What the submission should contain
- A description of the cooking process, the menu type, the appliance schedule and the hours of operation.
- An odour risk assessment reaching a stated control level, with the reasoning shown.
- Extract rate calculations, canopy design and duct sizing.
- The full filtration specification, including carbon volume and contact time.
- Duct route drawings on plan, section and elevation, with the termination detail.
- Discharge height and velocity, with a scale drawing showing the relationship to neighbouring roofs and windows.
- Plant noise assessment with measured background data and the proposed mitigation.
- A maintenance schedule naming the intervals for filter cleaning, carbon replacement and duct cleaning, and who will carry it out.
An Odour Assessment covers the first two and the reasoning behind the control level. A Ventilation and Extraction Statement covers the system design, the route and the termination. On a straightforward unit the two can sit in one document, provided the odour reasoning is not lost inside a specification.
Conditions, and life after permission
Expect conditions requiring the extraction scheme to be approved in writing before the use starts, installed as approved before first use, and maintained thereafter. A condition on hours of operation is common, and a condition requiring a maintenance log to be kept and made available on request is increasingly so.
The maintenance log matters. Where a complaint is made later, the log is the evidence that the system was being run as approved, and its absence shifts the argument.
Planning permission does not remove the statutory nuisance regime. Where odour or noise amounts to a statutory nuisance under environmental protection legislation, the council can act regardless of the permission, and compliance with a planning condition is not a complete answer.
Illustrative example. A vacant unit under two flats takes a lease for a fried chicken takeaway. The odour risk assessment reaches a high control level because of the frying and the flat directly above. The proposed duct terminates at first floor level in a rear yard. Redesigning the route to a vertical riser terminating above the ridge, with an electrostatic precipitator and a sized carbon bed, is what makes the application approvable. This example is illustrative only.
Before you sign the lease
Check the planning history for conditions restricting the use of the unit, since a condition limiting the premises to a former shop use survives the use class reforms and needs its own application to change.
Then walk the duct route with a ventilation engineer. If there is no way to get a duct to the roof without crossing a third party demise or a principal elevation, the unit is a poor candidate for hot food whatever the rent looks like.
Then set the planning case out in a short Planning Statement that deals with odour, noise, litter, servicing, parking and hours together, because those are the six matters the officer's report will cover.
This is general guidance, not legal advice. Check the position with your local planning authority and environmental health team before relying on it.
Enter your postcode on PlanScope to see which reports a hot food or restaurant change of use is likely to need.
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Frequently asked questions
Do I need planning permission for a hot food takeaway?
Yes. A hot food takeaway is a sui generis use outside the use class system, so a change from a shop, cafe or restaurant is a material change of use needing permission. The extraction ductwork normally needs permission as well, because it alters the external appearance of the building.
What decides the level of odour control required?
Four factors: the type of cooking, with frying, chargrilling and tandoor cooking at the high end; the scale of the kitchen and its hours; the proximity and sensitivity of receptors, with a flat above the unit the most sensitive of all; and the dispersion available from the building and its surroundings.
Are odour neutralising sprays acceptable?
Not as the primary system. Neutralising and masking agents change the character of the smell rather than removing the odour load, and environmental health officers treat a scheme that relies on them as unresolved. They can supplement a properly sized filtration train that already deals with the load.
Where should the extract discharge?
Vertically, at high level, terminating above the roof of the host building and clear of the roofline and openings of neighbouring buildings, at a high efflux velocity. Cowls and horizontal bends at the termination deflect the plume downwards and should be avoided. Low level discharge into a rear yard is the commonest reason for refusal.
Does planning permission protect me from odour complaints later?
No. The statutory nuisance regime operates independently, so the council can act on odour or noise that amounts to a statutory nuisance even where the installation matches the approved scheme. Keeping a maintenance log showing filter cleaning, carbon replacement and duct cleaning is the practical protection.
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.