Section outline: odour assessment for a hot food use

An odour assessment for a hot food premises is a short technical report with a fixed logic: describe what you will cook, identify who could smell it, grade the risk, then show an extraction and abatement design that answers that risk. The odour assessment hot food outline below follows the structure environmental health officers expect, drawn from the Defra guidance on the control of odour and noise from commercial kitchen exhaust systems and the risk-based approach in the air quality profession's odour guidance.

Write it in that order. Reports that lead with the equipment specification and work backwards to the receptors read as a sales brochure and get queried.

The proposed cooking process and its odour potential

Start with the menu, because the whole assessment flows from it. State the cooking methods, the equipment, the duty and the hours of operation.

The distinction that matters is between processes that produce heavy, persistent odour and those that do not. Charcoal grilling, deep frying, tandoor cooking, wok cooking with strong aromatics and anything involving fish or curry spices sit at the heavy end. Baking, reheating, light grilling and coffee sit at the light end. Councils know the difference and a report that describes a charcoal grill as light cooking loses credibility immediately.

Give the officer these facts in a short table: equipment schedule with kilowatt ratings, extraction volume in litres per second or cubic metres per second, hours of operation including any late-night trading, and the number of covers. Then state the grease and odour loading implied, in words rather than in invented numbers.

Where the proposal is a change of use, say what the lawful existing use is. A unit that was already a hot food takeaway is in a different position from a former shop, and the planning history belongs here rather than buried in a covering letter.

Receptor identification and separation distances

Receptors are the people who could reasonably be affected, and the plan showing them is the single most useful page in the report.

Identify every sensitive receptor within a sensible radius: residential windows, including those above and beside the unit, openable windows and ventilation inlets of other commercial premises, outdoor seating, school and nursery playgrounds, and any residential balcony or roof terrace. Mark the height of each one, because a window two floors up is a different problem from one at ground level. Measure the distance from the proposed discharge point to each, and state it.

Separation distance is not a pass or fail test on its own. It feeds the risk grading alongside the cooking type and the extraction arrangement. The point the guidance makes repeatedly is that discharge at low level close to a window cannot be solved by abatement alone, which is why the duct route needs resolving before any equipment is specified.

Flats above the unit are the hardest case. Where the only available duct route is through a residential building in separate ownership, say so plainly in the report and set out the alternative, because an officer who discovers that constraint later will refuse rather than condition it.

Risk based assessment approach

The accepted method grades the risk from three inputs and matches the abatement to the grade.

• The odour potential of the cooking process, from light to heavy.
• The proximity and sensitivity of receptors, taking account of height and the nature of the use.
• The dispersion available at the discharge point, which depends on termination height, position relative to the building envelope and efflux velocity.

Set the three out explicitly, state the resulting risk category, and then show the abatement level the guidance associates with that category. A report that announces a high risk and then proposes grease filters alone is internally inconsistent, and so is one that proposes a full electrostatic and carbon train for a coffee shop.

One honest caveat. Odour assessment is qualitative at this scale, and the risk grading involves judgement rather than calculation. Say so. An officer trusts a report that acknowledges the limits of the method more than one that presents a grading as though it were a measurement. Dispersion modelling is available for large or unusual installations, and the report should say why it is or is not proportionate here.

Extraction route, termination and discharge velocity

This is the section where applications are won and lost, because it is the part that cannot be retrofitted.

Describe the full route from canopy to discharge: canopy type and capture velocity, ductwork material and size, fan position and type, attenuation, access panels for cleaning, and the termination. Draw it on a section, not just on a plan.

Four design points carry the weight.

1. Termination height. Discharge at least a metre above the ridge or the highest part of the roof, clear of any adjacent higher building, and away from openable windows and air intakes. A termination at eaves level under a window is the classic refusal.
2. Discharge direction. Vertically upwards, uncapped or with a cap that does not deflect flow downwards.
3. Efflux velocity. Enough to carry the plume clear of the building envelope, commonly in the range of 10 to 15 metres per second at the outlet, with the figure stated and the fan selected to achieve it with the abatement in place.
4. Duct route and fire. A kitchen extract duct passing through other premises raises fire compartmentation issues that are a Building Regulations matter rather than a planning one, and the report should flag the interaction rather than resolve it.

A Ventilation and Extraction Statement usually carries this detail where the council asks for one, and on larger schemes it sits alongside the odour report rather than inside it.

Abatement selection and maintenance

Abatement is a train, not a single device, and each stage does a different job.

Grease filtration comes first, because grease carry-over destroys everything downstream. Baffle filters in the canopy, then a secondary filter stage for medium and high risk installations. Electrostatic precipitators remove fine particulate and some odour, and they need regular cleaning to keep working. Activated carbon adsorbs the odorous compounds and is the main odour control stage for high risk cooking, sized by contact time and air volume. Ultraviolet and ozone systems are sometimes proposed, and the report should be candid that their performance depends heavily on correct sizing and maintenance.

State the specification for each stage: filter class, carbon mass or bed depth, expected service life and replacement interval. Then state what happens when it is not maintained, which is the honest answer to the officer's real worry.

Maintenance frequency should follow the ventilation industry's grease hygiene guidance for ductwork cleaning, scaled to the hours of cooking. A premises frying for 14 hours a day needs a cleaning interval measured in months, not years.

Noise from the extraction plant

Odour and noise travel through the same equipment and are usually conditioned together, so a short noise section belongs in the report even where a separate assessment is also provided.

Cover the fan sound power level, the attenuation proposed, the position of the fan relative to residential windows, and the assessment against background sound levels under BS 4142. Night-time background levels govern where the premises trade late. Where the installation is substantial or the receptors are close, a full Noise Impact Assessment by a suitably qualified author is the right answer, and professional review is strongly advised for acoustic work.

Do not forget structure-borne transmission. A fan mounted on a shared floor slab or on a wall adjoining a bedroom will generate complaints no facade measurement picks up, and anti-vibration mounting should be specified rather than assumed.

Management and record keeping commitments

The last section converts the design into obligations the council can condition, and offering them yourself usually produces better wording than waiting for the officer's draft.

Commit to a named maintenance regime with intervals for filter change, carbon replacement and duct cleaning. Commit to keeping a logbook on the premises, available on request, recording each service with the date and the contractor. Commit to a commissioning test before first use, confirming extraction volumes and the noise level achieved. Offer a contact arrangement for complaints during trading hours.

Then set out the conditions you are content with, drafted tightly. A condition requiring the approved scheme to be installed before first use and maintained thereafter is manageable. A condition requiring an unspecified further scheme to be approved before opening is the kind that delays a fit-out by weeks, and the way to avoid it is the same discipline that gets a materials schedule discharged first time: submit the detail with the application.

The whole report should run to perhaps a dozen pages with a receptor plan, a duct section and an equipment schedule. Length is not what persuades an environmental health officer. A clear route from the menu to the termination point is. Where a draft of an Odour Assessment is produced with AI assistance, it needs a qualified reviewer to check the risk grading and the equipment sizing, because councils usually expect a suitably qualified author for this work.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. For specialist technical reports, qualified professional input may be required. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.