Short answer: A common logic is canopy grease separation first, finer particulate control such as an ESP or suitable mechanical filters next, then application-specific UV/oxidation and activated carbon treatment before discharge. The exact order is product- and project-specific and must also coordinate the fan, attenuators, fire strategy and safe access.
The sequence matters because a downstream technology can be damaged or rapidly exhausted by a contaminant that should have been removed earlier. Carbon exposed to heavy grease loses useful capacity and may create pressure problems. UV lamps coated with oil cannot deliver their intended output. An ESP without effective canopy filters can foul unnecessarily quickly.
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.
Start with grease separation at source
The canopy is the first opportunity to remove larger droplets close to the cooking process. Filters should be the correct type, correctly oriented and fitted without gaps. Regular cleaning is essential. This stage reduces—but does not eliminate—the grease reaching the duct and later treatment.
- Correct canopy filter type and orientation.
- No missing filters or unsealed gaps.
- Safe removal and cleaning routine.
- Grease collection and drainage kept clear.
Protect gaseous treatment with particulate control
Fine mechanical filters or an ESP can reduce smoke and smaller grease aerosol before activated carbon. Product arrangements vary, especially where UV is used for grease-vapour treatment. The supplier should show the purpose of each stage, the allowed loading and the pressure loss across clean and service conditions.
- Pre-filter where required by the selected equipment.
- ESP or fine filtration matched to airflow.
- UV components kept within their temperature and cleanliness limits.
- Carbon protected from oil and bypass.
Treat the fan and discharge as part of the sequence
Fan position changes the pressure regime through upstream and downstream equipment. Attenuators can foul if placed in a grease-laden stream. The terminal must support dispersion and weather protection. There is no safe universal diagram that overrides manufacturer instructions, the fire design or the real duct route.
- Coordinate fan access and cleanability.
- Avoid placing unsuitable acoustic media in contaminated air.
- Account for every stage in the pressure calculation.
- Finish with an appropriate discharge arrangement.
What the observation may be telling you
| Observation | What it may mean | Correct next step |
|---|---|---|
| Canopy baffle filters | Remove larger grease droplets first | Inspect and clean frequently |
| Panel/bag pre-filters | Protect later fine or carbon stages where specified | Monitor loading and pressure |
| ESP | Reduce fine grease and smoke particles | Clean cells and prove electrical operation |
| UV-C/oxidation | Application-specific grease/odour treatment | Maintain lamps and safety interlocks |
| Activated carbon | Polish suitable gaseous odour compounds | Prevent bypass and replace before exhaustion |
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
- Ask for a labelled airflow schematic.
- State the contaminant controlled by every stage.
- Include clean and loaded pressure losses.
- Confirm maximum temperature and grease-loading limits.
- Show service clearance for each component.
- Coordinate fan, controls and alarm sequence.
- Use the manufacturer-approved arrangement for the selected products.
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
- Putting carbon directly after a heavily loaded canopy without suitable protection.
- Assuming a HEPA label makes a filter appropriate for grease extract.
- Placing inaccessible disposable filters above ceilings.
- Ignoring UV lamp fouling.
- Rearranging proprietary stages to fit space without supplier approval.
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 carbon always be last?
It is commonly downstream of effective particulate control, but the exact arrangement must follow the system design and manufacturer requirements.
Can a bag filter replace an ESP?
They use different mechanisms and pressure characteristics. Either may be appropriate in a designed system, but they are not automatically interchangeable.
Where does the attenuator go?
Its location depends on construction, grease exposure, access and acoustic design. It should not become an inaccessible grease trap.
Related Kitchen Install Guide reading
- Commercial Kitchen Odour-Control Systems Guide
- Best Route for Commercial Kitchen Extract Ductwork
- What Should a Kitchen Extraction Quote Include?
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
- BESA: DW/172 Specification for Kitchen Ventilation Systems
- Purified Air: Commercial kitchen multi-filter units
- Purified Air: Commercial kitchen ESP systems
- 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.