Odour evidence for a bakery in a mixed use block

A bakery in a block of flats is an odour case that is usually won or lost on one drawing: the route of the extract duct. Bakery odour evidence planning work is straightforward technically, because the release points and the abatement options are well understood. What is not straightforward is getting a duct from a ground-floor unit to a discharge point above roof level through a building the applicant does not own. Where that cannot be done, no amount of filtration saves the application.

So the sequence is backwards from how most applicants approach it. Establish the flue route first, then design the system, then write the assessment.

Why bakery odour is treated as a nuisance risk at all

Bread smells pleasant, which leads applicants to assume there is no issue. Environmental health officers assess odour on the recognised factors of frequency, intensity, duration, offensiveness and location, and a bakery scores low on offensiveness and high on everything else.

The duration point is the one that matters. A bakery typically starts production between 3am and 5am, runs continuously, and discharges steam and volatile compounds for hours when residents above are asleep with windows open in summer. Baked bread at 4am stops being pleasant quickly.

Offensiveness also rises with the product. Laminated pastries and anything fried, such as doughnuts, release fat and acrolein rather than the compounds people associate with bread. Caramelised sugar and over-baked product produce burnt notes that generate complaints. A bakery that also operates a fryer is, for assessment purposes, closer to a hot food use than to a bread bakery.

Identifying the release points in a small unit

A small unit has more release points than the drawings usually show, and missing one is the commonest fault in a submitted assessment.

• Deck or rack oven steam vents, which discharge a large volume of hot moist air in short bursts at loading and at the end of a bake.
• The prover, which is low volume and continuous.
• A canopy over the bench or over any fryer, with its own grease load.
• General mechanical ventilation serving the unit.
• The shop front door, held open during trading, which is a release point nobody designs for.
• The rear door, opened for deliveries and waste.
• Passive vents and air bricks in the original fabric, often connecting into shared voids.

List them all, with volumes, in the assessment. An officer who finds an unlisted oven vent in the photographs stops trusting the rest of the document.

The flue route through a residential block

This is the controlling constraint. The recognised approach for commercial kitchen extraction is to discharge vertically, at high velocity, at a level above the roof or above the highest nearby openable window, so that the plume is carried clear rather than re-entrained at a window or balcony.

Three routes exist and all three have problems in a residential block.

An external duct up the rear or side elevation is the usual answer. It needs planning permission in its own right, because flues on commercial premises are not permitted development in the way domestic flues are, and it needs the freeholder's consent as an alteration to the structure. On a listed building or in a conservation area it needs a heritage case and will often be refused on the principal elevation.

An internal riser through the building requires space that rarely exists, consent from every leaseholder whose demise it crosses, and fire-stopping at every compartment floor to maintain the compartmentation of the block. Fire engineering input is needed, and in a higher-risk building the wider regulatory framework applies, as what a fire statement must cover at Gateway One explains.

Discharge at low level, at the back of the unit, is what applicants propose when the other two fail. It rarely succeeds where there are windows or balconies above, because the plume rises along the facade. Where it is the only option, the case has to rest on very high abatement performance plus a low-emission product range, and officers are rightly sceptical.

Settle the route before the lease is signed. A bakery fit-out where the landlord refuses a flue is an expensive discovery.

Abatement options and the maintenance that keeps them working

Abatement is selected against the assessed odour risk, and the recognised hierarchy runs from grease filtration through electrostatic precipitation, ultraviolet or ozone treatment, to activated carbon for the odour itself.

For a bread bakery with no frying, grease loading is low and carbon is doing most of the work. For a bakery with a fryer, a grease filter and an electrostatic precipitator come first, because fat blinds carbon quickly and an unmaintained carbon bed does nothing.

The part that gets skipped is maintenance, and it is what conditions will fix on. Carbon has a service life measured in operating hours and it degrades silently, so a system with no replacement schedule will be ineffective within a year. Expect a condition requiring the system to be maintained in accordance with a submitted schedule, with records kept and made available on request.

Put the schedule in the submission: filter change intervals, electrostatic cell cleaning frequency, carbon replacement by operating hours with the assumed hours stated, fan belt and impeller checks, and who holds the logbook. An Odour Assessment that specifies abatement without a maintenance regime has only solved half the problem.

Hours of operation as mitigation, and its limits

Conditions restricting hours are the usual mitigation offered, and for a bakery they are harder than they look.

Baking happens before trading. A condition restricting the hours during which the extraction system may operate therefore restricts production as well as trading hours, and a bakery that cannot run its ovens before 7am is not a bakery. Applicants sometimes accept such a condition to get permission and then breach it immediately, which is the worst outcome.

What is negotiable: the hours for deliveries and waste collection, which are usually the real source of complaint; the hours during which the rear door may be open; and a requirement that the shop front door be kept closed with mechanical ventilation making up the air.

Noise from the extract fan at 4am is frequently a bigger issue than the odour, and it is assessed separately against background levels. A Noise Impact Assessment covering the fan, the ovens' plant and the delivery activity should be submitted alongside, because an application that answers odour and ignores night-time plant noise invites a refusal on the other ground.

Lease and freeholder constraints, which planning does not solve

Planning permission authorises development. It does not give a right to fix a duct to someone else's wall or run it through someone else's demise.

For a leasehold unit in a block, check the lease for alterations provisions, whether the external walls and roof are within the demise or retained by the landlord, any absolute covenant against alterations, and whether a licence for alterations will be needed. Check also for a user clause restricting the permitted use of the unit, which can prohibit cooking or food preparation regardless of the planning position.

Where the block is managed by a residents' management company, consent means persuading the other leaseholders, who are also the people who will object to the application. Approaching them before submitting, with the flue route drawn and the abatement explained, tends to work better than meeting them at committee.

What environmental health will ask for

Prepare these and the consultation response is usually conditions rather than objection.

1. An odour risk assessment following the recognised approach for commercial kitchen exhaust systems, with the risk level derived rather than asserted, and the product range stated.
2. A system schematic showing every release point, duct sizes, the fan and its duty, the abatement in sequence, and the discharge point.
3. Extract volume calculations, with canopy face velocity and air change rate, and the discharge velocity at the terminal.
4. An elevation and section drawing of the flue, with the discharge height relative to the roof and to the nearest openable windows and balconies, dimensioned.
5. The abatement specification with manufacturer performance data, and the maintenance schedule.
6. A noise assessment of the fan and plant against measured background levels, at the nearest residential facade.
7. Evidence that the flue route is deliverable, which in practice means the freeholder's in-principle consent.

The last item is the one applicants omit and officers increasingly ask for. A Ventilation and Extraction Statement that sets out a flue the applicant has no right to install is a statement about a scheme that cannot be built.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Odour and acoustic assessment, and ventilation design, need a suitably qualified author, and councils expect one, so treat any draft as the starting point for that specialist. Enter your postcode on PlanScope to see which reports a change of use like this is likely to need.