A new restaurant can have a correctly sized canopy, fan and duct run, yet still be refused sign-off or receive complaints from neighbouring premises. The usual question at that point is: when is ESP required? The practical answer is that an electrostatic precipitator is required when the site, authority or discharge route demands a higher level of grease-smoke filtration than canopy baffle filters and standard ductwork can provide.
It is not a box that every commercial kitchen must fit as standard. Whether an ESP is necessary depends on the cooking process, where the air is discharged, the building’s planning conditions and the expectations of the local authority, landlord or managing agent. Getting that decision right before fabrication avoids costly changes to ductwork later.
What an ESP does in a kitchen extract system
An electrostatic precipitator, usually shortened to ESP, is an in-line filtration unit fitted within a commercial kitchen extraction system. It uses electrically charged collector cells to remove fine airborne grease, smoke and particulate from the extracted air.
Canopy filters are the first stage. They catch a proportion of the larger grease droplets before air enters the duct. An ESP handles the finer material that passes through those filters, which is why it is commonly specified where frying, chargrilling, wok cooking or other grease-laden processes are involved.
That distinction matters. An ESP is primarily a particulate and grease filtration solution. It is not, by itself, an odour-control system. Where odour is a concern, the extract design may also need activated carbon filtration, correctly selected discharge arrangements, or both. UV treatment may also be considered in some high-grease applications, but it has to be designed as part of the complete system rather than added as a substitute for sensible duct routing and regular cleaning.
When is ESP required by a project?
In most cases, the requirement comes from the site rather than a single blanket rule. A local planning condition may require kitchen extract air to be treated before discharge. An environmental health officer may expect additional filtration where the proposed outlet is close to residential windows, offices or other sensitive neighbours. A landlord may impose it to protect a building, particularly in multi-occupied retail or leisure premises.
An ESP should be treated as necessary where one or more of the following applies:
- The kitchen will produce substantial smoke or fine grease aerosol through frying, grilling, charbroiling or wok cooking.
- The discharge point is restricted, such as a dense town-centre location or a building with nearby flats and neighbouring businesses.
- The extract cannot reasonably terminate at a location that disperses air well away from people, windows and air intakes.
- Planning approval, a fit-out specification, lease condition or managing agent specifically calls for ESP filtration.
- The duct route passes through areas where reducing grease deposition is especially valuable for maintenance and fire-risk management.
The discharge route often decides the answer
The first question should not be, “Which ESP unit do we need?” It should be, “Where can the extract air go, and what will be around it?”
A direct, well-designed route to a suitable high-level discharge location gives contaminants more opportunity to disperse. If that route is available and the kitchen has modest cooking activity, an ESP may not be necessary. The system still needs appropriate canopy filtration, correctly sized ductwork, a suitable fan and a compliant installation, but extensive air treatment may not be justified.
The position changes when the discharge is close to occupied buildings or public areas. Air released near flats, neighbouring restaurants, offices, pedestrian routes or fresh-air intake grilles is more likely to cause a grease, smoke or odour nuisance. This is where ESP filtration becomes a sensible and often specified part of the design.
Do not assume that simply fitting a more powerful fan solves the issue. More extraction without suitable treatment can move more contaminated air towards the same problem location. Fan selection, duct size, filtration and discharge position have to work together.
High-grease cooking is the main trigger
The more grease and smoke a cooking process produces, the stronger the case for an ESP. Deep-fat frying, solid-fuel-style grilling, chargrilling and intensive wok cooking create fine airborne contaminants that can pass beyond primary canopy filters.
This material does not only affect the air outside. Over time, it can settle inside ductwork, on fan components and on downstream equipment. That increases cleaning demands and can contribute to fire risk if maintenance is neglected. An ESP reduces the amount of fine grease carried further into the system, but it does not remove the need for regular professional duct cleaning.
A kitchen serving mainly reheated, boiled or lightly cooked food may have a lower filtration demand than one producing fried food throughout service. Menu changes are therefore relevant. If a tenant later adds chargrilling or expands frying capacity, the original extract specification may no longer suit the operation.
ESP is not an alternative to DW172 design
An ESP should sit within a properly designed commercial kitchen ventilation system, not compensate for an undersized canopy or poor duct installation. DW172 provides the recognised guidance for kitchen ventilation design and sets expectations around capture, containment, ductwork and access for cleaning.
The canopy must first capture the cooking plume effectively. Its size, overhang, filter arrangement and mounting height all affect performance. The ductwork should then be designed and fabricated to an appropriate standard, with practical access points for inspection and cleaning. DW144 is relevant to the quality and construction of ductwork, while DW172 addresses the kitchen ventilation application.
If grease-laden air escapes the canopy into the kitchen, installing an ESP downstream will not fix the working environment. Staff may still experience heat, fumes and poor comfort, while the fan works harder than it should. Likewise, poorly sealed duct joints or unsuitable bends can undermine an otherwise capable filtration unit.
Specify the complete system, not just the ESP
Before selecting an ESP, establish the canopy dimensions, cooking equipment layout, expected duty, duct route, fan position and available installation space. The unit must be matched to the airflow the system is designed to handle. Oversizing or undersizing can affect filtration performance, pressure resistance and operating cost.
Access is equally important. ESP collector cells require regular cleaning to remain effective. If a unit is boxed into a ceiling void or positioned where cells cannot be safely removed, maintenance will be delayed and performance will deteriorate. A practical installation includes service clearance, an electrical isolation arrangement and a maintenance plan agreed from the start.
There are trade-offs in location too. Installing filtration indoors can make servicing straightforward, but it requires sufficient space and consideration of noise, heat and access. External positioning may free up kitchen space, although weather protection, electrical supply and service access still need to be resolved. The right answer depends on the premises rather than a standard drawing.
Filtration does not remove ongoing responsibilities
An ESP can reduce grease and smoke released through the extract route, but it needs cleaning and inspection at suitable intervals for the cooking load. Dirty collector cells can restrict airflow and reduce effectiveness. They may also create unnecessary resistance for the fan.
The same principle applies to the rest of the installation. Canopy filters need routine cleaning, ductwork needs professional cleaning at intervals appropriate to the cooking process, and the fan should be checked as part of planned maintenance. Keep service records. They are useful evidence for insurers, landlords, managing agents and environmental health discussions.
Where odour is part of the concern, monitor the full system rather than assuming the ESP is at fault. Saturated carbon filters, changes to the menu, blocked canopy filters or a damaged fan can all alter how the system performs.
A practical way to make the decision
For a new kitchen or refurbishment, obtain the proposed menu and cooking equipment list before finalising the extract package. Then assess the available discharge route and any planning, landlord or authority requirements. If the operation is high-grease or the discharge is close to sensitive neighbours, allow for ESP filtration early enough to provide proper access and suitable duct connections.
CanopyMan manufactures commercial extraction canopies and ductwork in Birmingham, with standard and made-to-measure options available for projects across England and Wales. Standard canopies are produced in 430-grade stainless steel at 0.7mm thickness, while 304-grade stainless and alternative thicknesses can be specified where the site or application calls for them.
The best time to decide on an ESP is before the canopy, duct route and fan are fixed. A short review of the cooking process and discharge constraints at design stage is far less disruptive than trying to add filtration after complaints, failed approval or a difficult handover.