Commercial kitchen extraction and ventilation: what the rules and guidance expect

What does the law actually require for kitchen ventilation?

Several pieces of law touch a commercial kitchen extract system, but none of them is a design specification. As Winchester City Council's planning guidance puts it, there is no legislation directly governing the design and performance of commercial kitchen ventilation systems. The duties come from elsewhere:

• Workplace ventilation. The Workplace (Health, Safety and Welfare) Regulations 1992 require every enclosed workplace to be ventilated by a sufficient quantity of fresh or purified air. HSE's catering sheet applies this directly to kitchens, which produce fumes, vapour and a lot of heat.
• Gas safety. Under the Gas Safety (Installation and Use) Regulations 1998, where an extract system acts as the flue for a gas appliance, HSE says it is treated as a flue and needs an interlock linking the airflow to the gas supply.
• Fire safety. The responsible person for non-domestic premises must carry out a fire risk assessment and keep it under review. Grease in ductwork is one of the hazards that assessment should cover.
• Nuisance and planning. Councils can act against food premises that cause a nuisance under the Environmental Protection Act 1990, and they assess odour and noise when an extract system needs planning permission.

HSE's catering guidance is not compulsory, but HSE says that following it will normally be enough to comply with the law. That makes it the practical baseline for owners, operators and the contractors they appoint.

What should a well-designed extract system do?

HSE's catering sheet on kitchen ventilation lists the objectives. A good system removes cooking fumes at the appliance, removes excess heat and brings in cool, clean air, avoids uncomfortable draughts, supplies enough air for complete combustion, stays easy to clean and runs quietly. The design has to account for the cooking load, the amount of equipment, the layout of the kitchen, the number of staff and how the system will be cleaned and maintained.

The detailed industry reference is BESA's DW/172, which BESA describes as the definitive industry standard for designing, installing and maintaining commercial kitchen ventilation systems. The second edition was published in October 2018, adding new sections on solid fuel appliances, demand-controlled kitchen ventilation and recirculation systems, and a May 2024 addendum updated the guidance on fire-resisting and smoke-control ductwork.

A documented design matters later on. HSE notes that a fully specified system, with a record of its design performance as DW/172 requires, makes it much easier for owners, caterers and gas engineers to check whether the ventilation suits the cooking load. Keeping records of design criteria, commissioning results, maintenance needs and test results is part of the same advice.

How are canopies and extract rates worked out?

The principles in HSE's guidance are straightforward:

• every appliance and other source of fumes and heat should sit under a canopy hood
• the hood should be as close as possible to the source, allowing for the work being done
• the hood must be big enough, with enough extraction, to minimise fumes spilling into the kitchen
• the extraction rate is best calculated from the information supplied with the appliances, taking account of the air change rate the kitchen needs

Where there is no canopy, for example with a ventilated ceiling, HSE says a competent heating and ventilation engineer should calculate the rates. DW/172's 2018 edition expanded the appliance coefficient schedules used for airflow calculation, which is why designers usually work from the appliance schedule rather than a rule of thumb.

Councils sometimes set their own minimums. The London Borough of Bromley's guidance, for example, asks for canopies to extend 250mm beyond the edge of the cooking equipment. It is worth checking whether your local authority publishes similar requirements before the design is fixed.

Why does make-up air matter so much?

Every cubic metre of air an extract fan removes has to be replaced. HSE's guidance says the design should account for replacing extracted air, by mechanical or natural means, and that the replacement air should be fresh and come from outside. It should not be drawn from dirty areas such as bin stores, and it should not upset the flues serving gas appliances.

The safety point is carbon monoxide. HSE says adequate make-up air is particularly important for gas-fired and solid fuel appliances, because a shortage can lead to combustion products building up. Smaller kitchens may get enough air through grilles in walls, doors or windows, but HSE suggests a fan-and-filter system is more suitable for larger installations. Bromley's guidance, as one council example, asks for a dedicated make-up air system of roughly 85% of the extract flow.

Make-up air also controls heat. HSE suggests directing cooler incoming air towards hot work positions and, if that is not enough, considering air conditioning or fixed fans that do not disturb fume extraction. Freestanding fans are not normally an effective way to provide make-up air. For a broader view of supply and extract systems, see the overview of commercial ventilation and heat recovery.

How do gas interlocks work, and when are they needed?

An interlock links the mechanical ventilation to the gas supply so that if the ventilation fails, the gas to the appliances shuts off. HSE's gas safety sheet says the installer should have fitted the appropriate interlocking system between any mechanical ventilation and the gas appliances, and that manual bypasses of interlocks are not permitted.

For new work, HSE's ventilation sheet asks designers to assess the need for an interlock based on a competent person's assessment of the risks. For older kitchens, HSE accepts that BS 6173 is not retrospective, but where there is no interlock it expects the risk to be assessed and then prevented or controlled. Any work on the gas appliances themselves must be done by a Gas Safe registered engineer, and HSE describes annual inspection as a reasonable minimum for catering gas equipment.

Where carbon monoxide alarms are fitted, HSE says they should sound an audible alarm and be interlocked to an automatic gas shut-off that needs manual intervention to restore the supply.

What will the council look at for odour and noise?

Planning requirements vary between councils, so the two examples below show the kind of evidence to expect rather than a national rule.

• Odour risk assessment. Bromley points applicants to the EMAQ+ 2018 guidance on odour and noise from commercial kitchen exhausts, whose Annex C risk assessment is used to decide the level of odour control needed. Winchester recommends that applications consider the same guidance.
• Discharge height and direction. Bromley says ducting should extend at least one metre above the eaves and warns that low-level discharge is likely to be refused. Winchester says discharge should ideally be 1m above the roof ridge and vertically upwards, unimpeded by flue terminals. HSE separately warns against devices that direct discharge downwards.
• Efflux velocity. Bromley asks for a final discharge velocity of at least 12 m/s to help dispersal.
• Unknown cooking type. Where the future food type is not known, Winchester says the installation should be designed for the highest level of odour control.
• Noise. Bromley asks for system noise to be calculated using BS 4142 methods, and Winchester notes that a noise report will usually be required because ventilation plant can introduce a new noise source.

Winchester's list of information for an application is a useful checklist: details of the premises and cooking, scaled plans showing the fans and filters, filter specifications, hood dimensions and velocities, flue design, a noise report and a maintenance schedule.

How often should extract ductwork be cleaned?

BESA's TR19 Grease specification sets minimum cleaning frequencies based on how many hours a day the kitchen operates:

Kitchen use	Hours per day	Minimum cleaning frequency
Heavy	12 to 16	Every 3 months
Moderate	6 to 12	Every 6 months
Light	2 to 6	Every 12 months

These are minimums. BESA says the actual frequency should be set by a competent person's cleanliness risk assessment, taking account of the type of cooking and the results of deposit thickness testing. TR19 Grease aims to keep grease deposits below a mean of 200 microns between cleans, and areas at 500 microns or more need immediate spot cleaning.

Cleaning covers the whole route: canopy, fan and the full length of ductwork, with access panels fitted where parts were previously unreachable. Bromley's guidance asks for panels at 3.0m centres. Verification normally includes before-and-after photographs from the same positions and a post-clean report, which insurers and fire safety officers may ask to see.

Odour control equipment has its own schedule. Bromley's guidance, for example, recommends changing pre-filters every two weeks, carbon filters every four to six months and cleaning electrostatic precipitators every four weeks. Mechanical ventilation as a whole should be maintained in line with the manufacturer's or installer's instructions.

Operators comparing contractors for design, installation or maintenance can request quotes through the site's form. Restaurant owners can also read about cooling for restaurants, and the guide to commercial ventilation requirements covers general workplace ventilation outside the kitchen. For supply, extract and heat recovery plant beyond the canopy, see commercial ventilation systems.

Sources

• Ventilation in catering kitchens (Catering Information Sheet No 10, rev 3), Health and Safety Executive, checked 20 October 2026
• Gas safety in catering and hospitality (Catering Information Sheet No 23, rev 3), Health and Safety Executive, checked 20 October 2026
• DW/172 Specification for Kitchen Ventilation Systems, BESA Publications, checked 20 October 2026
• Kitchen Extract System Cleaning for Fire Safety Compliance (TR19 Grease), BESA, checked 20 October 2026
• Food and Drink Premises: planning requirements for kitchen extraction/ventilation systems, London Borough of Bromley, checked 20 October 2026
• Odour Assessment Guidance 2024, Winchester City Council, checked 20 October 2026
• Workplace fire safety: your responsibilities, GOV.UK, checked 20 October 2026
• The Workplace (Health, Safety and Welfare) Regulations 1992, regulation 6, legislation.gov.uk, checked 20 October 2026

Common questions

Can a kitchen use a recirculating canopy instead of ducting to outside?

Recirculation systems have their own section in DW/172 since the 2018 edition, so they are a recognised option. Whether one suits a particular kitchen depends on the appliances, especially gas appliances that rely on the extract as a flue, and on what the council will accept.

Who is responsible for extract cleaning in a leased restaurant?

Fire safety duties fall on the responsible person, which can include the employer, owner, landlord or occupier. Where more than one person has responsibilities, government guidance says they have to work together, so the lease and the cleaning contract should say who books and pays for TR19 cleans.

Does an all-electric kitchen need a gas interlock?

The interlock requirements in HSE's guidance relate to gas appliances. An all-electric kitchen still needs effective ventilation under the workplace regulations and still has to meet any council odour and noise conditions.

What paperwork should a kitchen operator keep?

HSE recommends keeping records of the design criteria, commissioning performance, maintenance requirements and tests. For cleaning, TR19 Grease reports normally include before-and-after photographs, any deposit thickness results and a certificate, which insurers may ask to see.

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