Kitchen operations · Design & fit-out
Ductwork and gas are the least movable objects on any kitchen plan. A layout that starts with the discharge route, the capture zone and the interlock costs a fraction of one that discovers them at fit-out.
Why services come first
Most kitchen layouts are planned back to front: equipment first, workflow second, and the extraction and gas retrofitted around whatever is left. It is the most expensive order of operations in catering. Ductwork has to route through a real building - risers, fire compartments, a discharge point that will not feed cooking smells into the flat upstairs - and the gas supply arrives where the meter and pipe runs allow. Those two services are the least movable objects on the plan, which means a layout that starts with them costs a fraction of one that discovers them at fit-out.
The governing document for the ventilation side is DW172, the BESA specification for kitchen ventilation systems, which sets out how canopies, filtration, ductwork and discharge should be designed for the appliances underneath. The practical consequence for layout is simple: the heavy cooking lives inside the canopy's capture zone, and the capture zone is not generous. Guidance works to the canopy overhanging the appliance line by at least 300mm to the front and sides, with the hood mounted around two metres from the floor. Move a fryer half a metre out from under that footprint and you have not adjusted a layout - you have exited the ventilation design.
The gas layer
Gas appliances in a commercial kitchen do not stand alone. Under BS 6173 - first introduced in 2001 and revised since, most recently in 2020 - gas should not be available in the kitchen unless the ventilation is running, enforced by a gas interlock that proves the extract is working before the gas solenoid opens. The proving is done either by an air-pressure differential switch in the ductwork or by a current monitor on the fan supply. Any kitchen built or substantially refurbished since 2001 is expected to have one, along with a clearly labelled manual shut-off and flame supervision on the appliances.
For layout, the interlock creates a dependency chain worth drawing on the plan: gas appliances sit under the canopy, the canopy connects to a duct route with a viable discharge, and the interlock wires the whole assembly together. Splitting gas cooking across two zones means two capture solutions and interlock logic that covers both. It also means the extract is now operationally critical - if the fan fails or the ductwork chokes, the gas goes off and the kitchen stops. That is the safety system working as designed, and it is also the strongest commercial argument for keeping the system maintained rather than discovering the dependency mid-service.
A duct route is not finished when the air moves - it has to be cleanable for the life of the kitchen. TR19 Grease expects access panels positioned so all of the ductwork can be reached, with guidance pointing to panels roughly every two metres and at both sides of bends, fitted on the side of the duct where possible. Long concealed runs above fixed ceilings, risers with no access, ducts buried behind new partitions: these are layout decisions that turn a routine clean into a dismantling job for decades. If the plan shows a duct nobody could reach with a panel, the plan is not done - a point worth checking against how often that ductwork will actually need cleaning once the kitchen trades.
Putting it together
Start at the roof, not the floor. Fix the discharge point and duct route first, because they are constrained by the building and the neighbours. Second, place the canopy under that route, sized to the appliance schedule - and be honest about the schedule, because a canopy designed for a six-burner range will not lawfully cover the chargrill added next year. Third, arrange the heavy cooking inside the capture zone in the order the workflow wants: fryers and grills where the effluent is heaviest, lighter equipment at the edges. Fourth, run the gas to the line with the interlock, manual shut-off and meter access positioned where a chef can reach them, not behind the combi. Only then lay out prep, wash-up and storage in the space that remains - they are movable; the services are not.
Finally, balance the air. Extract without make-up air turns a kitchen into a vacuum that whistles at door gaps, starves the interlock and drags in unfiltered air from wherever it can. DW172 expects supply air to be designed alongside extract, and a layout should reserve the route for it. The kitchens that feel calm at full tilt are not lucky - the air was planned as carefully as the cookline it serves.
Questions
Only if the canopy and duct system were designed for it. The extract is sized to the appliance schedule under DW172, and the canopy's capture zone should overhang the line by at least 300mm. Adding a chargrill or fryer outside that footprint, or beyond the system's design load, means re-checking the ventilation - and DW172 guidance expects replaced appliances to be interlocked too.
Any kitchen built or substantially refurbished since BS 6173 was introduced in 2001 is expected to have one. The interlock proves the ventilation is running - via a pressure switch in the duct or a current monitor on the fan - before gas is available at the appliances, alongside a labelled manual shut-off and flame supervision devices.
It means the duct route must be cleanable, not just installable. TR19 Grease expects access panels positioned so all ductwork can be reached - guidance points to roughly every two metres and at both sides of bends - so concealed runs, inaccessible risers and ducts buried behind partitions are layout mistakes that cost money at every clean for the life of the kitchen.
Phoenix Duct Clean · by the numbers
Get the duct route surveyed before the walls close. We clean and certificate extraction systems to TR19 Grease - and we know exactly where access panels need to be.