Noise or odour: which assessment a kitchen needs

A new kitchen in a commercial unit usually needs both: a noise assessment for the plant and an odour assessment for the cooking smells, even though they come out of the same flue. They measure different things against different criteria and they produce different planning conditions. Where the unit is small and the nearest window is close, environmental health will read both and will condition both separately.

The order you commission them in matters, because the background noise survey sets a design target that the fan selection has to meet, and fan selection affects the duct and the odour control equipment it can accommodate.

What each assessment measures

A Noise Impact Assessment for a kitchen is about plant and activity: the extract fan, the refrigeration condensers, the air conditioning units, deliveries, and in some cases patrons outside. The method for plant is the British Standard for rating and assessing industrial and commercial sound, which compares a rating level for the source against the measured background sound level at the nearest noise sensitive receptor.

An Odour Assessment is about the cooking process: what is being fried or grilled, how much of it, how far the nearest receptor is, and what abatement and dispersion the system provides. There is no numerical limit to test against in the way there is for noise, so the assessment is risk based.

Different units, different criteria, different conclusions. A system can be quiet and smelly, or clean and audible, and most refusals of restaurant applications turn on one of the two rather than both.

Plant noise and the background comparison

The background sound level is the number that controls everything. It is measured at the nearest sensitive window over representative periods, including the night if the kitchen will run late, and it is the statistical background rather than the average.

The rating level of the plant is then calculated from the manufacturer's sound data, the distance, the directivity, any screening and any correction for the character of the sound. A fan with a pronounced tone, or an intermittent compressor, attracts a penalty that raises the rating level above the bare sound pressure.

The standard treats an excess of around 10 dB over background as an indication of a significant adverse effect, and an excess of about 5 dB as an indication of an adverse effect, with context taken into account throughout. Context does real work: the same plant in a quiet residential street and beside a main road produce different conclusions.

The condition that commonly follows limits the cumulative rating level of all plant at the nearest residential facade to the background level, or to a figure a few decibels below it. Design to that figure rather than hoping to argue it later, because retrofitting attenuation into a completed installation is expensive and sometimes impossible within the available space.

Odour risk and extraction design

The accepted approach for commercial kitchens follows the government guidance on the control of odour and noise from commercial kitchen exhaust systems. It scores the risk from the type of food cooked, the size of the kitchen and the separation distance to the nearest receptor, and converts that into a required level of odour control: from no abatement for low risk situations through to high level abatement for high risk ones.

The abatement stages are grease filtration first, then carbon filtration, with electrostatic precipitation, ultraviolet or ozone systems used in combination where the risk is high. None of them work without maintenance, which is why the maintenance schedule is part of the submission rather than an afterthought.

Dispersion is the other half. Terminating the flue at high level, usually above the roof line and clear of openable windows and air intakes, does more for odour impact than another filter stage. A system discharging at first floor level into a courtyard will fail however well filtered it is.

Where one document can cover both

For a single small unit, a combined Ventilation and Extraction Statement often carries the whole case: the system schematic, the fan and duct specification, the odour risk assessment with the abatement proposed, the termination details, the acoustic calculation for the plant, and the maintenance regime.

That works where the risk is modest and the receptors are not immediately above. It stops working where there is a flat directly over the unit, where the background is very low, or where the authority's validation list asks for separate reports.

Ask the case officer which form they want before commissioning. The distinction between the two assessments for a restaurant is explored further in noise or odour assessment for a restaurant, and the answer changes with the receptor geometry.

What environmental health asks for

The list is consistent across authorities, because the officers are checking the same things:

1. A schematic of the full extract system from canopy to termination, with duct sizes and route.
2. Fan make, model, duty point, and manufacturer's sound power data.
3. The odour risk assessment with the scoring shown and the abatement specified.
4. Termination height and position relative to openable windows and air intakes.
5. Acoustic calculations for all plant, cumulative, at the nearest sensitive facade.
6. A maintenance schedule naming filter change intervals and who carries them out.
7. Grease management and cleaning arrangements.
8. Proposed operating hours for the kitchen and the plant.

Submit all eight with the application. Each missing item is a consultation response, and each consultation response is a fortnight.

Conditions that follow each assessment

Expect separate conditions, because they control separate things and they are discharged by different evidence.

The odour condition typically requires the extraction and abatement scheme to be installed in accordance with approved details before the use starts, and retained and maintained thereafter. The noise condition typically sets a cumulative rating level at a defined location, sometimes with a post-installation verification test required within a stated period of first operation.

That verification test is the one that catches operators. A system that was designed to the condition but installed with the attenuator omitted will fail the test, and the remedy is at the operator's cost.

Commissioning order for a small unit

Do it in this sequence and the design converges instead of looping:

1. Commission the background noise survey, including night periods if late opening is proposed.
2. Carry out the odour risk assessment from the menu, kitchen size and receptor distances.
3. Set the design targets: a plant noise limit and a level of odour control.
4. Design the system to both, checking that the duct route and termination are physically achievable.
5. Write the assessments against the designed system rather than an aspiration.
6. Agree the form of submission with the case officer and environmental health before validation.

Step four is where schemes fail quietly. A high risk kitchen needing carbon filtration and a high level termination cannot always be fitted into a unit with a 2.4 metre ceiling void and a listed rear elevation, and finding that out after the lease is signed is an expensive discovery.

To see which documents a food and drink change of use is likely to need, enter your postcode on PlanScope.

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.