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How Often Should Kitchen Extraction Be Cleaned?
If you run a commercial kitchen, sooner or later someone will ask when the extraction was last cleaned. It might be your insurer, an environmental health officer, a landlord or a fire risk assessor. The honest answer for most kitchens is “less often than it should have been”, usually because nobody was sure what the right interval was.
This guide sets out the cleaning intervals used across the industry, explains why cooking hours matter more than the size of the kitchen, and covers the signs that a system needs attention before the next scheduled visit.
The short answer: 3, 6 or 12 months
TR19 Grease, the guidance published by the Building Engineering Services Association (BESA), links cleaning frequency to how heavily the kitchen is used. The widely used intervals are:
| Kitchen use | Typical daily cooking hours | Suggested cleaning interval |
|---|---|---|
| Heavy | 12 to 16 hours | Every 3 months |
| Moderate | 6 to 12 hours | Every 6 months |
| Light | 2 to 6 hours | Every 12 months |
These figures are a starting point, not a guarantee. They assume a reasonably designed system with working grease filters that are cleaned regularly. Two kitchens with the same opening hours can build up grease at very different rates.
Why cooking hours matter more than kitchen size
Grease does not come from the size of the canopy. It comes from what is being cooked, how it is cooked and for how long. A small takeaway frying chicken and chips from lunchtime until midnight can load its ductwork faster than a large hotel kitchen that mostly steams, bakes and reheats.
The cooking methods that produce the most airborne grease are:
- deep frying, especially with shared oil used across long shifts
- chargrilling, solid-fuel grills and tandoor ovens
- wok cooking at high temperature
- griddles and flat-top plates used continuously
- rotisserie and kebab equipment
If your menu leans on any of these, assume you sit at the heavier end of the table, even if your opening hours suggest otherwise.
Measuring grease rather than guessing
Time-based intervals are useful for planning, but the better approach is to measure. TR19 Grease uses a wet film thickness test, where a technician takes readings with a calibrated comb gauge at set points along the system. Results are recorded in microns (µm).
The two thresholds most often referred to are:
- 200 µm average across the readings, at which point the system should be cleaned
- 500 µm at any single point, which calls for prompt attention
Readings taken before and after each clean give you evidence that the interval is right. If the “before” readings keep coming in well under 200 µm, the interval may be longer than you need. If they are already high three months after the last clean, the schedule should tighten. You can read more about what a good report contains in our guide to TR19 compliance for commercial kitchens.
Signs your extraction needs cleaning sooner
Do not wait for the calendar if you notice any of these:
- grease dripping from the canopy edge, light fittings or filter housing
- filters that look clogged again within days of being washed
- smoke or steam rolling out from under the canopy instead of being drawn up
- cooking smells lingering in the dining area or reaching neighbours
- the extract fan sounding louder, rougher or laboured
- oily staining around the discharge point outside or on the roof
- a kitchen that feels hotter than usual during service
Several of these point to grease restricting airflow, which also makes the system work harder and wears out the fan. Our article on why a kitchen extract stops pulling properly goes through the common causes.
Filters are not the same as the system
Washing baffle filters every week is good practice, and it slows down grease reaching the ductwork. It does not replace a professional clean. Filters capture a portion of the grease, but fine particles and vapour still pass through and condense inside the plenum, ducts and fan.
A common situation we see: a kitchen with spotless filters and a canopy that looks clean, while the duct a metre above the filter bank has a thick, tacky coating that nobody has looked at in years. That hidden grease is what fuels duct fires. We cover filter care in more detail in how to clean baffle grease filters.
What your insurer and fire risk assessment expect
Under the Regulatory Reform (Fire Safety) Order 2005, the responsible person for a commercial premises must assess fire risks and take reasonable steps to reduce them. Grease build-up in kitchen extraction is a well-known fire risk, so your fire risk assessment should address it.
Many commercial insurance policies go further and include specific conditions about extract cleaning, often referring to TR19 and to a cleaning interval. If a fire starts in the extraction and you cannot show the system was cleaned as required, a claim may be reduced or refused. Check your policy wording, and keep every report and certificate where you can find it quickly.
Setting the right interval for your kitchen
A sensible approach looks like this:
- Start with the TR19 interval that matches your cooking hours.
- Ask for grease readings before and after every clean.
- Review the “before” readings after two or three visits.
- Adjust the interval up or down based on the evidence, and record why.
- Check your insurance policy in case it sets a stricter requirement.
Our planned maintenance option books visits in advance at the interval that suits your kitchen and reminds you before each one, so the schedule does not slip when the kitchen gets busy.
Frequently asked questions
Is TR19 a legal requirement?
TR19 Grease is industry guidance rather than law. However, the legal duty to manage fire risk sits with the responsible person under the Fire Safety Order, and insurers commonly make TR19 cleaning a policy condition. In practice, following it is the clearest way to show you have managed the risk.
Can we clean the ductwork ourselves?
Kitchen staff can and should clean canopies and filters day to day. Ductwork, fans and risers need proper access, isolation of the fan and specialist equipment. They also need independent readings and a written report, which is what your insurer will ask to see.
Does a cleaning certificate last for a fixed period?
No. A certificate records the condition of the system on the day it was cleaned. Grease starts building up again as soon as cooking resumes, which is why the interval matters.
What if part of our ductwork cannot be reached?
That is common in older buildings. A good report states clearly which sections could not be accessed and why, and recommends access panels where needed. Inaccessible sections are still a fire risk, so they should not be quietly left off the record.
Book a clean or a review of your current schedule
Duct Clean London cleans kitchen extraction systems across North West, West and Central London, with visits arranged around your opening hours. Send us your postcode, opening hours and a few photographs of the canopy, filters and fan, and we will suggest a sensible interval and quote for the work.
Call 07843 141416, email [email protected] or request a free quote online. You can also read more about our TR19 cleaning service in London.