Odour assessment competence and who can sign one

Odour assessment competence in planning is not regulated, so the question is what the environmental health officer will accept rather than what a statute requires. For a commercial kitchen the officer is looking for an author who can do three things: characterise the odour source from the menu and the cooking method, judge dispersion from the proposed discharge point to the nearest sensitive receptor, and specify abatement at a level that matches the risk. Most refusals on odour grounds follow an assessment that did the third thing and skipped the second.

The person who sells you the extraction system is rarely the right person to write it.

What the assessment has to do

A commercial kitchen odour risk assessment follows the approach set out in the Defra-commissioned guidance on the control of odour and noise from commercial kitchen exhaust systems, which pairs an odour risk estimate with a prescribed level of abatement. The method asks for the cooking type and scale, the proximity and sensitivity of receptors, the discharge height and location relative to those receptors, and the dispersion characteristics of the surroundings.

Out of that comes a risk category and a corresponding abatement specification, running from basic grease filtration up to combinations of electrostatic precipitation, carbon filtration and ultraviolet or ozone treatment. Discharge height and termination are treated as part of the mitigation rather than as a fixed constraint, which is why a flue taken to roof level can reduce the filtration needed.

The guidance is a framework rather than a calculation. Two people applying it to the same restaurant can reach different abatement conclusions, and the difference lies in how they read the receptor and dispersion inputs. That is the judgement the officer is testing.

For larger or more unusual sources the Institute of Air Quality Management's guidance on assessing odour for planning is the wider framework, and it is the document to follow where the source is not a kitchen at all.

Ventilation designers and air quality consultants compared

Two trades write these documents and they are good at different halves of the job.

On a straightforward unit with a tall flue clear of neighbouring windows, a competent ventilation designer's statement is often enough. On a mid-terrace unit with flats above, a shared rear elevation and an existing odour complaint history, it will not be, and the officer will ask for an assessment by someone who can reason about dispersion.

The sensible appointment on a difficult site is both, with the air quality consultant setting the performance requirement and the ventilation designer meeting it. A ventilation and extraction statement that combines the two reads very differently from one written by either alone.

Professional membership in air quality

There is no licence, and no protected title. What exists is specialist membership.

Membership of the Institute of Air Quality Management, at associate, full or fellow grade, is assessed and carries a code of conduct. Many practitioners also hold Chartered Environmentalist status through a licensed body, or chartered membership of an engineering or environmental institution. For acoustics, which usually travels with odour on kitchen applications, membership of the Institute of Acoustics is the equivalent signal.

Ask three questions before appointment. Which grade of membership is held, and in which institute. How many kitchen odour assessments has the author produced in the last two years. And has the author ever defended one at appeal.

That last question separates people quickly. An assessment written by someone who has been cross-examined on one reads differently.

Our note on checking a consultant's membership and currency covers how to verify a claimed grade rather than taking it on trust.

The supplier conflict

The most common arrangement in the sector is that the extraction supplier writes the odour assessment that justifies the equipment it is quoting for. Nobody hides this. It still creates a structural problem.

The supplier has an interest in the specification it can deliver at the price the client has accepted. If the honest answer is that the discharge point is unacceptable and the flue needs to rise two storeys to roof level at four times the cost, the assessment that says so loses the supplier the job.

I am not suggesting dishonesty. The effect is subtler: borderline inputs get read favourably, the receptor chosen is the second nearest rather than the nearest, and the dispersion commentary is thin because it is the part that would undermine the conclusion.

Three ways to manage it. Commission the assessment separately from the installation, so the author has no stake in the specification. Or accept a supplier-authored assessment and pay for a short independent review of the inputs. Or require the supplier to state the assessment author's membership and professional indemnity position in writing, which tends to concentrate minds.

Where liability matters, our note on liability when one party writes and another submits sets out who carries what.

Verification after installation

An assessment is a prediction. Conditions on these permissions increasingly require the installed system to be verified, and that is a separate competence again.

Verification typically covers measured extract volumes against design, filter pressure differentials, the sealing and route of the ductwork, the discharge velocity and direction, and a commissioning record signed by the installer. Where the abatement includes carbon, a maintenance and replacement schedule is the condition that gets discharged late and causes most of the subsequent complaints.

The specification for kitchen ventilation systems published by the building engineering services sector is the reference installers work to, and asking for compliance with it by name in the appointment is more effective than asking for "good practice".

Put the maintenance regime in the application. An officer who can see a signed commitment to filter replacement intervals has less reason to impose a tighter condition.

And be realistic about who will carry it out once the restaurant is trading. Carbon filters that are never changed are the single most common cause of an odour complaint on a system that passed its commissioning test, and the complaint lands on the operator rather than on the installer who left two years earlier.

What to require in the appointment

Specify the output, the standard, the author and the independence.

Name the guidance the assessment must follow. Require the nearest sensitive receptor to be identified by address and distance, with a plan. Require the discharge point height and direction to be stated as a drawing rather than described. Require the risk category and the resulting abatement to be set out explicitly, with the reasoning for the receptor and dispersion inputs. State who signs it, with their membership grade. And require professional indemnity cover appropriate to the value of the fit-out.

An odour assessment is a report type councils usually expect a suitably qualified author to prepare, and professional review is strongly advised. PlanScope can produce an AI-assisted draft structured to UK planning policy, with site-specific inputs flagged for completion, which gives that professional a starting point rather than a blank page.

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.