Short answer: An ESP primarily removes fine grease and smoke particles. Activated carbon adsorbs suitable gaseous odour compounds. UV-C-based systems support oxidation of grease and odorous compounds under controlled conditions. Because the pollutant mechanisms differ, a high-risk kitchen may use more than one stage rather than choosing a single winner.
Kitchen exhaust is a mixture of heat, moisture, grease droplets, fine particles, smoke and volatile compounds. A specification that calls every box an odour filter hides the most important question: which contaminant is each stage intended to control? The correct sequence normally protects sensitive downstream treatment from grease and makes maintenance possible.
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.
ESP: fine particulate control
Electrostatic precipitation charges and collects fine oil mist and smoke. It can reduce the load reaching the duct and later treatment stages. It needs electrical energisation, clean collector cells, correct airflow and a safe wash programme. It should not be credited with universal removal of gaseous cooking odours.
- Best aligned with fine grease aerosol and smoke.
- Washable collector cells rather than disposable media.
- Performance deteriorates when cells are dirty, damaged or bypassed.
- Requires controls, alarms and safe electrical isolation.
Activated carbon: gaseous-phase polishing
Activated carbon uses a porous adsorbent to retain suitable molecules on its internal surface. Its useful life depends on carbon type and mass, contact time, temperature, humidity, contaminant concentration and the quality of upstream particle removal. Once capacity is used, the media must be replaced; appearance alone rarely proves remaining life.
- Targets suitable gaseous and odorous compounds.
- Needs effective upstream grease and particle control.
- Requires a defined media quantity and contact-time basis.
- Has a finite capacity and replacement cost.
UV-C and oxidation systems
UV-based kitchen systems vary. Depending on design, ultraviolet energy may break down grease vapour and support oxidation of odorous compounds, sometimes with ozone present within the duct. Output, exposure time, lamp cleanliness, airflow, interlocking, materials and residual oxidant control all matter. UV lamps are not passive components: they age and foul.
- Requires correct wavelength, output and exposure conditions.
- Lamp surfaces must remain clean enough to transmit energy.
- Safety interlocks and access controls are essential.
- Residual ozone and discharge conditions require competent assessment.
What the observation may be telling you
| Observation | What it may mean | Correct next step |
|---|---|---|
| Canopy baffle filter | Larger grease droplets | First-line grease separation; not fine-smoke or odour treatment |
| ESP | Fine grease aerosol and smoke particles | Particle control; protects downstream stages |
| UV-C/oxidation | Selected grease vapours and odorous compounds | Application-dependent; needs controlled exposure and safety systems |
| Activated carbon | Suitable gaseous odour compounds | Final polishing stage with finite media capacity |
| Discharge design | Exposure at nearby receptors | Dispersion measure, not a filter, but often crucial to the result |
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
- Define the cooking pollutants before choosing equipment.
- Show the proposed order of every treatment stage.
- State airflow, clean and loaded pressure losses and fan duty.
- Provide evidence for the claimed performance under relevant conditions.
- Describe interlocks, alarms and failure indication.
- Document cell, lamp and carbon maintenance tasks.
- Confirm how the discharge location supports dispersion.
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 percentage claims without test conditions.
- Placing carbon directly in a heavy grease stream.
- Treating reduced visible smoke as proof that odour is solved.
- Ignoring the different replacement and cleaning costs.
- Specifying UV or ozone without safe access and interlocking.
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
Which technology is best?
There is no universal best. The answer depends on pollutant type, risk, airflow, space, discharge and the maintenance the operator can sustain.
Can carbon go before an ESP?
That is rarely a robust arrangement for grease-laden kitchen extract because carbon benefits from effective upstream particulate control. The project designer should confirm the sequence.
Can filtration compensate for a poor discharge?
Sometimes treatment can reduce risk, but it should not be assumed to neutralise a constrained low-level or recirculating discharge. Dispersion remains part of the design.
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
- Defra: Commercial kitchen exhaust odour and noise guidance
- Purified Air: Commercial kitchen ESP systems
- Purified Air: Commercial kitchen multi-filter units
- Purified Air: Commercial kitchen UV-O systems
- 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.