Short answer: Odour can continue because the selected technology treats the wrong pollutant, the airflow is outside its range, contaminated air bypasses the media, carbon is exhausted, ESP/UV stages are dirty or disabled, cooking duty exceeds the design, or the discharge exposes nearby receptors despite treatment.
The phrase “filtration installed” does not prove a performance outcome. A box may contain only particle filters while the remaining problem is gaseous odour. The correct equipment may also be undermined by missing seals, overloaded airflow, low fan duty or poor maintenance. Diagnosis should follow the treatment train from capture to terminal.
Important: This guide explains design questions; it is not a product selection, planning approval or performance guarantee. A competent designer should assess the actual kitchen, air system, discharge and maintenance conditions.
Was the system designed for the actual problem?
Check the original risk assessment, equipment schedule and proposed treatment sequence. If the design assumed light reheating but the operator installed fryers and a chargrill, the installed plant may be performing exactly as selected while the source has changed. Conversely, a carbon panel may have been presented as a complete high-duty solution without enough media or pre-filtration.
- Compare approved and actual appliances.
- Compare planned and actual hours/throughput.
- Identify particle versus gaseous treatment.
- Review claimed performance and test basis.
Is air actually passing through effective treatment?
Air can bypass around poorly fitted cells, frames, doors or temporary gaps. Fan shortfalls can reduce canopy capture, while excessive flow can reduce residence time through treatment. Measure the system and inspect physical fit rather than assuming air follows the drawing.
- Confirm filter and cell orientation.
- Inspect blanking plates and door seals.
- Measure total and branch airflow.
- Check loaded pressure and fan operating point.
Has performance degraded?
Carbon has finite capacity; ESP cells and UV lamps foul; lamps age; pre-filters load and controls fail. Maintenance records should show whether the system has remained within its service regime. If no baseline or service history exists, create one before making repeated component changes.
- Carbon replacement date and media identity.
- ESP cell-cleaning and alarm history.
- UV lamp hours, cleaning and replacement.
- Canopy-filter and duct condition.
What the observation may be telling you
| Observation | What it may mean | Correct next step |
|---|---|---|
| Odour existed from day one | Design, installation or commissioning deficiency likely | Review basis and measured performance |
| Odour returns gradually | Media exhaustion or maintenance degradation | Service complete treatment train |
| Only peak periods affected | Duty/airflow capacity may be exceeded | Compare peak use with design |
| Odour at one nearby window | Dispersion or downwash may dominate | Review terminal and receptor geometry |
| Odour after menu change | Pollutant and load changed | Reassess filtration and planning basis |
A practical evidence workflow
Planning evidence and commissioning evidence answer different questions but should describe the same installed system. The first explains why the proposal should control impact; the second proves what was actually fitted and how it performed on the day of test.
- Freeze the operating brief. Record appliances, fuel, menu, hours, peak demand and delivery constraints. Note assumptions that may change, such as a future chargrill or later opening hours, because they can alter both treatment duty and planning risk.
- Issue a coordinated specification. Align the drawings, equipment schedule, treatment stages, duct route, discharge, access, acoustic measures, utilities, controls and maintenance requirements. Assign responsibility for every interface.
- Inspect before concealment. Photograph labels, access panels, fire-rated penetrations, drains, isolators, controls and service clearances. Resolve substitutions against the approved performance requirement rather than accepting a similar-looking unit.
- Commission and close out. Measure airflow and relevant pressure, electrical, water, gas, temperature or control values. Record test conditions, instruments and defects. Retest corrective work and provide the operator with the final evidence set.
Keep a useful record: Use a controlled index for drawings, calculations, product data, approvals, test sheets, certificates, photographs, training and maintenance information. Mark superseded versions clearly. A concise, traceable pack is stronger than hundreds of unindexed pages.
Project or service checks
- Trace the air path from canopy to discharge.
- Identify the job of each treatment stage.
- Measure extract and replacement air.
- Inspect for bypass and missing components.
- Review maintenance against actual hours.
- Check cooking and menu changes.
- Record findings before buying additional equipment.
Turn the agreed checks into named deliverables. Each item should have an owner, due date and acceptance method. Where a measurement is required, record the value, unit, instrument or source, operating condition and result. This makes the information usable at handover and during a later investigation.
Common mistakes to avoid
- Adding more carbon without checking airflow.
- Increasing fan speed without checking treatment limits.
- Assuming no alarm means the ESP or UV is effective.
- Ignoring discharge downwash.
- Treating a neighbour complaint as a public-relations issue only.
Avoid closing the issue on appearance alone. A new filter, reset controller or revised drawing may change the symptom without resolving the underlying duty, utility, access or maintenance problem. Confirm the completed work under a representative operating condition and keep the evidence with the asset or ventilation record.
Frequently asked questions
Should the installer guarantee zero odour?
Absolute zero-odour promises are rarely credible. The contract should define design basis, treatment performance, commissioning and maintenance obligations.
Can a bigger carbon filter fix the problem?
Possibly if gaseous treatment is the limiting issue, but not if the source is bypass, airflow, smoke particles or poor dispersion.
Who should diagnose the system?
A competent ventilation/filtration specialist should coordinate measurements and product checks, with planning or environmental input where receptor impact is involved.
Related Kitchen Install Guide reading
- Commercial Kitchen Odour-Control Systems Guide
- What Is an EMAQ+ Kitchen Odour Assessment?
- What Should a Kitchen Extraction Quote Include?
Capture the installation and commissioning detail
Use the KIG 318 Commercial Kitchen Installation Checklist to record interfaces, checks, outstanding actions and the evidence needed at handover.
Sources and further guidance
- EMAQ+: Control of Odour and Noise from Commercial Kitchen Exhaust Systems
- GOV.UK: How councils deal with nuisance smells
- Purified Air: Commercial kitchen ESP systems
- Purified Air: Commercial kitchen multi-filter units
- Purified Air: Commercial kitchen UV-O systems
Last reviewed: 14 August 2026. This article provides general commercial-kitchen design information. It does not replace a site-specific ventilation design, manufacturer instructions, risk assessment, planning conditions or advice from a competent specialist.