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Extraction cleaning - the law
People want a legal number for how often to clean their ductwork. The law does not give one - and understanding why it does not is the key to getting the frequency right.
The short answer
No law sets a specific interval for cleaning kitchen extract ductwork. What fire safety law - the Regulatory Reform (Fire Safety) Order 2005 - requires is that you assess and manage the fire risk, and a grease-laden duct is a clear one. So the law expects cleaning at whatever frequency keeps that risk controlled, which in practice means following the recognised TR19 Grease bands and what your fire risk assessment supports.
Why there is no legal number
It is natural to look for a legal cleaning frequency, but fire safety law does not work that way. The Regulatory Reform (Fire Safety) Order 2005 places a duty on the responsible person to assess and reduce fire risk - it defines the outcome required, not the specific tasks or timings to achieve it. It never says clean your ductwork every so many months.
This is deliberate. A takeaway frying all day and a village hall used occasionally face very different fire risks from their extract systems, and a single fixed interval would be wrong for both. By setting a risk-based duty rather than a fixed number, the law expects the frequency to match the actual risk - which is more demanding than a flat rule, not less.
What the duty translates to
If the duty is to manage the grease-fire risk, then the law effectively expects the ductwork cleaned often enough to keep that risk under control. Grease is combustible and accumulates in the concealed runs, so letting it build unchecked is failing to manage a risk the assessment should have identified. The legal expectation is a cleaning frequency that keeps grease from reaching a dangerous level.
In practice that means following the recognised standard. The TR19 Grease bands - roughly three, six or twelve months by cooking hours - are how the industry translates the risk into an interval, and they are what a fire risk assessor, an enforcing authority and an insurer will all expect to see followed. Meeting the legal duty and following the standard amount to the same thing.
Where the assessment comes in
The document that actually pins down your cleaning frequency is your fire risk assessment. It should identify the extract ductwork as a fire risk and set out how that risk is controlled - which includes the cleaning regime and its frequency. So the legal expectation is not an abstract number but whatever your assessment, done competently, concludes is needed for your premises.
That is why the assessment and the cleaning are linked. A change that affects the grease load - a new fryer, busier trading, longer hours - is a reason to revisit both the assessment and the interval. Keeping the assessment current and cleaning to the frequency it supports is how the legal duty is actually met, page and practice together.
What enforcement looks for
If an enforcing authority ever looks at your premises, they are not checking a clean against a fixed legal date - they are asking whether the fire risk is being managed. A grease-laden, neglected system with no cleaning history is the failure they act on; a system cleaned to a sensible risk-based frequency, with certificates to show it, is the managed risk the law wants.
So the evidence matters as much as the cleaning. Dated certificates showing the system cleaned at intervals matched to its use demonstrate that the duty is being met continuously. The absence of any such record, on a system that is obviously overdue, is what turns a legal expectation into an enforcement problem.
The practical answer
So the honest answer to how often the law expects your ductwork cleaned is: as often as managing the fire risk requires, which in practice means following the TR19 Grease bands and your fire risk assessment. There is no shortcut number, but there is a clear route - assess the risk, set the interval to your cooking hours, clean to it, and keep the evidence.
Approached that way, you are not guessing at a legal figure that does not exist; you are meeting the duty the law actually sets. And because insurers require essentially the same thing, cleaning to the recognised frequency satisfies the law and the policy at once.
Questions
No law sets a specific interval. The Regulatory Reform (Fire Safety) Order 2005 requires you to manage the fire risk, so the law expects cleaning often enough to control it - in practice following the TR19 Grease bands and your fire risk assessment.
Because the law is risk-based. A busy takeaway and an occasional-use kitchen face very different risks, so a fixed number would be wrong for both. The duty is to match the frequency to the actual risk.
The recognised TR19 Grease bands - roughly 3, 6 or 12 months by cooking hours - which is how the industry translates the risk into an interval and what assessors, enforcers and insurers expect to see.
Your fire risk assessment. It should identify the ductwork as a risk and set out the cleaning regime and frequency that controls it, matched to how your kitchen actually cooks.
Whether the fire risk is being managed - a system cleaned to a sensible risk-based frequency with certificates to show it, rather than a fixed legal date. A neglected system with no history is the failure they act on.
Yes. Insurers require essentially the same thing, so cleaning to the recognised TR19 frequency and keeping certificates satisfies the legal duty and the policy condition at once.
We set a risk-based interval, clean to TR19 Grease and certificate it - so the legal duty is met and evidenced.
