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Fire safety - the extract duct
A fire risk assessment walks the whole building, and when it reaches the kitchen it does not stop at the visible surfaces. The extract duct - the enclosed run carrying grease through the structure - is exactly the kind of hidden fire path an assessor is trained to look for.
The short answer
A fire risk assessor looks at the kitchen extract duct as a potential fire path: an enclosed run carrying combustible grease through the building, capable of letting a fire travel through the structure. They will consider the grease build-up in the system, whether it is being cleaned on an adequate cycle, and whether fire dampers and other protections are in place and maintained. Crucially, they look for the evidence - cleaning records and reports - that shows the risk is actually being managed rather than merely assumed.
Why the duct
A fire risk assessment exists to identify how a fire could start, grow and spread in a building, and to check the measures controlling those risks. When the assessment reaches a commercial kitchen, the extract duct stands out, because it is precisely the kind of thing that concerns a fire risk assessor: a concealed run of ductwork, carrying combustible grease, passing through the building's structure - potentially through walls and floors meant to contain a fire. To a trained assessor, that is not just a duct, it is a ready-made path for fire to travel.
So the assessor approaches the extract duct as a fire-spread risk to be understood and controlled. The questions are how much combustible grease is in it, whether it could carry a fire through the building, and what is being done to keep that risk in check. It is one of the less visible items in a building's fire risk - out of sight inside the structure - which is exactly why an assessor knows to look at it rather than take the clean-looking kitchen surfaces at face value.
Grease build-up
The first thing the assessor is concerned with is the grease itself, because grease is the fuel that makes the duct a fire risk. They will want to understand how much grease has built up inside the ductwork and fan, since a heavily grease-laden duct is both more likely to have a fire and more able to sustain and spread one. The build-up is the hazard, and its extent is central to how serious the assessor judges the risk to be.
Because the grease is inside enclosed ductwork, the assessor often cannot simply see it - which is where evidence becomes important. They will look for indications of the grease condition and, above all, for the records of cleaning that show the build-up is being kept under control. A system with no evidence of its internal condition is a blind spot in the fire risk assessment, and an assessor will treat an uncleaned, unverified duct as an uncontrolled fuel load until shown otherwise.
Cleaning and protections
Beyond the grease itself, the assessor looks at whether the risk is being actively managed. Is the extract system being cleaned on a cycle appropriate to how heavily the kitchen cooks, so grease does not accumulate to a dangerous level? Where the ductwork passes through fire-resisting walls and floors, are fire dampers fitted to close the duct against fire, and are they being tested and maintained so they would actually work? These are the controls that turn a fire path into a managed risk.
An assessor is essentially checking that the building has a system for keeping the duct's fire risk under control, not just a duct that happens to look alright on the day. Regular cleaning on an adequate interval, fire dampers in place and tested, and the whole thing documented - that is what a well-managed extract fire risk looks like from the assessor's point of view. The absence of those controls, or of any evidence of them, is what the assessment will flag as a gap needing action.
The records
Running through all of this is the assessor's need for evidence, because a fire risk assessment is only as good as what can be demonstrated. A verbal assurance that the duct gets cleaned is weak; a set of cleaning reports showing the system cleaned on a proper cycle, with the condition recorded, is strong. Records of fire damper testing likewise show those protections are maintained. The documentation is what lets the assessor conclude the risk is genuinely controlled rather than merely claimed.
This is why cleaning records matter beyond the cleaning itself - they are the evidence a fire risk assessment relies on for the extract duct. A kitchen that can produce a clear history of extract cleaning and damper testing gives the assessor exactly what they need to sign off the duct as a managed risk. One that cannot leaves the assessor to record it as an uncontrolled or unverified hazard. The records are how the work of controlling the risk becomes visible in the assessment.
The takeaway
When a fire risk assessor reaches your extract duct, they see a concealed, grease-laden fire path through the building, and they assess it as such: how much combustible grease is in it, whether it is being cleaned adequately, whether fire dampers protect the points where it crosses fire barriers, and whether all of that is being maintained. It is one of the hidden risks a good assessment is specifically there to catch.
What satisfies the assessor is a managed risk backed by evidence - the system cleaned on an interval matched to the cooking, dampers in place and tested, and the records to prove both. Keeping the extract clean and documented is therefore not only a fire-safety measure in its own right but the thing that lets your fire risk assessment sign the duct off as controlled. Control the fuel, protect the path, and keep the records - that is what the assessor is looking for.
Questions
They see it as a fire path - a concealed, grease-laden run through the building - and assess how much combustible grease is in it, whether it is cleaned adequately, whether fire dampers protect where it crosses fire barriers, and whether it is all maintained.
Because it is an enclosed run carrying combustible grease through the building's structure, potentially through walls and floors meant to contain a fire. That makes it a ready-made path for a fire to travel - exactly what an assessor is trained to look for.
By its extent - a heavily grease-laden duct is more likely to have a fire and more able to spread one. Because the grease is hidden inside the ductwork, they rely heavily on cleaning records to show the build-up is being kept under control.
An adequate cleaning cycle matched to how heavily the kitchen cooks, fire dampers fitted and tested where the duct crosses fire barriers, and the whole thing documented - the controls that turn a fire path into an actively managed risk.
Because the assessment is only as good as what can be demonstrated. Cleaning reports showing the system cleaned on a proper cycle, with the condition recorded, are the evidence that lets the assessor conclude the risk is genuinely controlled rather than assumed.
The assessor is likely to treat the duct as an uncontrolled or unverified hazard, because they cannot see the grease inside it and have no evidence it is managed. A clear cleaning and damper-testing history is what lets it be signed off as controlled.
We clean extract ductwork on an interval matched to your kitchen and provide the reports an assessor relies on - turning a hidden fire path into a documented, managed risk.
