Costing an odour assessment for a kitchen or waste use

The cost of an odour assessment turns on one early decision: whether the local planning authority will accept a qualitative, risk based appraisal or insist on dispersion modelling. A single kitchen extract serving a 60 cover restaurant is a short piece of work. The plume from a waste transfer station with housing 150 metres downwind is a different exercise, with a site survey, emission rate derivation and software time behind it. Both arrive on a fee proposal under the same heading. They are not the same job, and the gap between them is the main thing an occupier should be asking about before signing anything.

Risk based appraisal against dispersion modelling

Published odour guidance for planning, including the Institute of Air Quality Management's guidance on odour and planning, sets out a tiered approach. You start with source, pathway and receptor. If the source is well understood, the abatement is conventional and the nearest sensitive receptor is far enough away, a reasoned qualitative assessment against that framework is proportionate and usually accepted.

Modelling enters when the authority cannot be persuaded on judgement alone. That tends to happen with intensive livestock, composting, anaerobic digestion, sewage treatment, rendering and larger waste handling, or where an environmental health officer has a complaint file open on the site already.

The move from the first row to the third is not incremental. Modelling brings a different skill set and a different piece of software, and the fee reflects both.

Source characterisation is where the hours go

Writing the report is the quick part. Characterising the source is not.

For a commercial kitchen the assessor needs the menu, the cooking methods, the appliance schedule, the extract volume in cubic metres per second, the duct route and the proposed abatement train. Charcoal grilling and wok cooking sit at the difficult end. Steam and boiling sit at the easy end. An assessor who is handed a mechanical drawing with the fan duty marked can price the work confidently. One who is handed a floor plan and a promise that the kitchen layout is still being worked out will either price defensively or come back for a second round of fees.

For a waste use the equivalent inputs are tonnages, waste streams, residence times, whether handling is inside a building under negative pressure, and the proposed biofilter or scrubber design with its residual concentration. Deriving an emission rate in odour units per second from that is specialist work and it is often the single largest line in the fee.

Receptor sensitivity and the benchmark chosen

The assessment has to say who is affected and how sensitive they are. A high sensitivity receptor is somewhere people have a reasonable expectation of not being exposed to odour, such as a dwelling, a school, a hospital or a hotel. Industrial neighbours sit lower down the scale.

The benchmark concentration applied at those receptors depends on how offensive the odour is. Guidance distinguishes between odours that are most offensive, moderately offensive and less offensive, and the acceptable exposure level falls as offensiveness rises. Choosing the benchmark is a judgement call the assessor has to defend, and an officer who disagrees with that choice can unravel an otherwise sound report.

Receptor survey time scales with the number and spread of neighbours. Twelve dwellings on one boundary is a morning's work. A town centre site with flats above and behind, a nursery across the road and a beer garden at 45 degrees is not.

Abatement design and the cost that follows it

The report will specify abatement, and the specification carries a capital cost that dwarfs the assessment fee. For a kitchen that usually means a grease filter stage, then carbon, sometimes with ultraviolet or ozone upstream, plus a fan selected to overcome the added resistance. Carbon needs replacing on a schedule, so the revenue cost matters as much as the installation.

An honest assessor will tell you early if the abatement that would satisfy the officer does not fit in the ceiling void you have. That conversation is worth paying for.

Where a formal statement of the extract system is required, the Ventilation/Extraction Statement and the Odour Assessment often get commissioned together, because the second depends on the design fixed in the first.

Discharge height changes the architecture

Odour guidance and the dispersion physics both point the same way: get the discharge high, clear of the building wake, and vertically upwards. For a terraced high street unit that means a duct running up the rear elevation to roof ridge level, which is a planning question in its own right because it is a visual alteration, and in a conservation area or on a listed building it is a larger one.

Discharge height is therefore not a detail to settle after permission. It changes the drawings, the structural fixings, the landlord consent and the party wall position. An assessment that assumes ridge level discharge and a design that assumes a louvre at first floor level will not agree, and the reconciliation happens at your cost.

An illustrative example

Take a vacant Class E(b) unit in a Victorian parade, with flats above the two neighbouring shops, proposed as a charcoal grill. Illustrative only: the odour work would reasonably cover an appliance schedule, an extract duty, a three stage abatement train, a duct route to ridge level at the rear, a receptor survey of the flats and the rear gardens, and a qualitative assessment against the offensiveness benchmark. The modelling route would only be reached if the environmental health officer refused to accept the qualitative case. Two different fees, same address.

Complaint history widens the brief

If the premises or a predecessor has generated complaints, the brief grows. The assessor will want the complaint records, any abatement notice or informal warning, and the history of what was fitted and when. And baseline odour surveys by a trained panel, or sniff testing along a transect, may be added. That is a field exercise with repeat visits in different wind conditions, so it is priced by the day.

Complaint history also changes the tone of the submission. You are no longer arguing that an effect is unlikely. You are arguing that a specified change will fix something the council has already seen, which is a higher bar and a longer report.

Scope it with environmental health before you commission

The least expensive version of this work is the one whose scope the officer has already agreed. Most authorities will discuss odour at pre-application stage, and the question to ask is narrow: will a qualitative risk based assessment be accepted for this use at this address, or is modelling expected. Get the answer in writing and attach it to the assessor's brief.

A few practical steps, in order:

1. Fix the appliance schedule and extract duty with the mechanical designer before asking for fees.
2. Identify every high sensitivity receptor within roughly 100 metres, including upper floor windows and outdoor amenity areas.
3. Ask the environmental health team which approach they expect and record the reply.
4. Confirm the duct route and discharge point with the landlord and the building owner.
5. Then commission the odour assessment, with the abatement specification as a deliverable rather than an afterthought.

Odour work sits alongside the other fees a change of use attracts, and the application fee itself is set by floorspace and site area rather than by the technical evidence you submit. If conditions later need adjusting, the fee position for section 73 and section 96A applications is different again.

Councils normally expect an odour assessment to be written by someone with relevant air quality or environmental consultancy experience, and professional review is strongly advised before submission. PlanScope can draft the structure, the policy framing and the receptor narrative in minutes, and its pricing is one free report, £50 per report or £150 per month on the Professional tier, with the specialist inputs still coming from your designer and assessor.

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.