Short answer: An ESP can reduce smoke and fine grease particles, which may reduce part of the perceived emission, but many cooking odours are volatile gaseous compounds that pass through a particle collector. Site-specific gaseous treatment and suitable discharge may therefore still be required.
This distinction explains a common complaint: the plume looks cleaner after an ESP is installed, yet neighbours can still smell the cooking. The system may be doing its particulate job while the design has not adequately addressed gas-phase odour, discharge dispersion, cooking intensity or maintenance of downstream stages.
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.
Particles and gases behave differently
Smoke contains particles that can be charged and collected. Smell can be created by molecules present as gases or vapours. A particle-control efficiency cannot simply be applied to those gaseous compounds. The contaminant mixture also changes between frying, chargrilling, spices, baking and solid-fuel cooking.
- Visible smoke is not the same measurement as odour.
- Grease aerosol is not the same as a volatile organic compound.
- Different menus produce different chemical and particulate loads.
- Human odour response occurs at concentrations that may not be visible.
Why the ESP is still valuable
Removing fine grease before a carbon or UV stage can protect it from fouling and extend useful performance. It can also reduce downstream duct deposits and visible emissions when correctly designed and maintained. The mistake is not using an ESP; it is giving it credit for every pollutant in the exhaust.
- Controls a significant particulate fraction.
- Protects later treatment from some grease loading.
- Supports a staged treatment train.
- Needs its own cleaning, alarms and commissioning.
The other parts of odour control
Activated carbon or another suitable gaseous treatment may be needed, while UV-based systems require application-specific design and controls. High-level unobstructed discharge can improve dispersion. The EMAQ+ approach considers cooking type, kitchen size, receptor proximity and dispersion, which prevents technology from being selected in isolation.
- Assess cooking and hours of operation.
- Review distance and relationship to sensitive receptors.
- Select gaseous treatment for the actual compounds and duty.
- Design discharge rather than relying only on boxes in the duct.
What the observation may be telling you
| Observation | What it may mean | Correct next step |
|---|---|---|
| Smoke reduced, smell unchanged | Particle control works but gaseous odour remains | Review carbon/UV treatment and discharge |
| Odour worsens over months | Carbon saturation, dirty lamps/cells or changed cooking may be involved | Inspect maintenance records and actual operation |
| Only neighbours below roof level complain | Dispersion and plume downwash may be important | Review terminal location and surrounding buildings |
| Odour occurs at peak service only | Treatment may be undersized for simultaneous cooking load | Compare peak duty with design assumptions |
| Odour appears when filters are bypassed | Poor fit or maintenance procedure is defeating treatment | Restore seals and approved components |
A practical design and handover workflow
Treat the filtration unit as one component of an air system. A dependable design starts with the cooking process and ends with a maintainable discharge, rather than starting with a catalogue airflow. The following workflow gives the client, designer and installer a shared audit trail.
- Define the source. List every appliance, fuel, cooking method, duty, diversity assumption and operating period. Chargrilling, frying and light reheating do not create the same grease, smoke or odour load. Record the future menu where the tenant is not yet trading.
- Establish the air duty. Calculate the extract volume and capture arrangement, then record the expected operating range. Check make-up air, duct velocity, leakage class, fan curve and the resistance of clean and loaded treatment stages.
- Select the treatment train. State what each stage is intended to remove, the evidence used for selection and the conditions attached to any performance claim. Include bypass sealing, controls, interlocks, alarms and the effect of failure.
- Prove and maintain it. Commission airflow and functions at the installed condition. Give the operator baseline readings, access instructions, cleaning intervals, consumables and a clear trigger for inspection or replacement.
Keep a useful record: Keep the approved drawing, design airflow, fan duty, clean pressure readings, control cause-and-effect, commissioning results and maintenance log together. When performance changes, comparison with this baseline is more useful than replacing parts by guesswork.
Project or service checks
- State separately what controls grease, smoke and gaseous odour.
- Use the real menu and peak operating pattern in the assessment.
- Review discharge height, velocity and nearby structures.
- Confirm carbon media quantity or UV design basis.
- Record ESP, lamp and carbon service dates.
- Investigate changes to equipment or menu.
- Avoid promising zero odour without a defined performance basis.
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
- Using an ESP particle-efficiency claim as an odour claim.
- Removing carbon because the plume looks cleaner.
- Ignoring a poor low-level discharge.
- Waiting for neighbour complaints before checking maintenance.
- Adding fragrance or masking products instead of correcting the source.
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
Can an ESP reduce some smell?
It may reduce odour associated with captured particles, but it should not be treated as complete gaseous-odour removal.
Is carbon always required after an ESP?
Not universally. The need depends on the risk assessment and performance objective, but carbon is a common gaseous polishing stage.
Why can people smell cooking when no smoke is visible?
Many odorous compounds are gaseous and detectable at very low concentrations, so visibility is not a reliable odour test.
Related Kitchen Install Guide reading
- Commercial Kitchen Odour-Control Systems Guide
- What Is an EMAQ+ Kitchen Odour Assessment?
- Where Should a Commercial Kitchen Extract Duct Discharge?
Plan the whole commercial kitchen, not one isolated component
Use the Commercial Kitchen Install Guide to coordinate extraction, equipment, utilities, drainage, safety, access and handover before work reaches site.
Sources and further guidance
- EMAQ+: Control of Odour and Noise from Commercial Kitchen Exhaust Systems
- Defra: Commercial kitchen exhaust odour and noise guidance
- Purified Air: Commercial kitchen ESP systems
- Camfil: Activated carbon media and contact time
- Extechnology: ESP, carbon, ozone and kitchen extract treatment
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.