Phoenix Journal · Ductwork
A story about the smallest part of a kitchen extract system - a hand-sized access panel - and how one of them made the difference between a documented clean and a building at risk. Here is what it teaches every responsible person about grease, access and TR19 Grease.
Field notes · kitchen extract
The most important part of a commercial kitchen extract system is often the cheapest one - a small, hinged access panel that lets someone actually see inside the duct.
This is a short story about one of those panels, and about the run of ductwork behind it that nobody had looked at in years. It is not dramatic. No alarm sounded. But it is the kind of quiet near-miss that decides whether a building keeps trading or spends a winter behind hoarding. The lesson underneath it is simple: you cannot clean, measure or prove the safety of anything you cannot reach.
When a run of extract duct has proper access, an engineer can open it, inspect it and measure it against a recognised standard. When it does not, everyone is guessing. Here is what opening one overlooked panel actually revealed, and why each point matters.
The panel in question was not a lucky extra. It was there because someone, at some point, followed the guidance in TR19 Grease - the Building Engineering Services Association (BESA) specification for managing the fire risk from grease accumulation in kitchen extraction systems. That document is the reference point UK insurers, property owners and enforcing authorities now expect you to work to.
TR19 Grease is specific about access, and the detail matters. Access panels should be positioned so that the whole of the ductwork can be reached and inspected, at intervals of roughly every two metres along the run, and at every point where the duct changes direction and grease tends to gather. Where it can be done, panels go on the side of the duct; the top or underside are a last resort, sealed carefully so grease cannot weep out. Each panel should be the same material as the ductwork and fixed with quick-release catches, in line with the ductwork construction standard DW144. In other words, a good panel is not a hole cut with tin snips - it is a designed, sealed, reusable opening.
The run in our story had one panel doing the work of several. It opened onto a stretch that should have had two or three more. That single panel was enough to reveal the problem; it was not enough to clean the whole length properly. So the honest outcome was not just a clean - it was a recommendation to fit further access before the next visit, recorded in writing. If you want to understand where these openings ought to sit and why their placement is a design decision rather than an afterthought, our guide on where to put access panels when designing ductwork walks through it in full.
Under the Regulatory Reform (Fire Safety) Order 2005, the responsible person for a premises must assess and reduce fire risks - and grease build-up in an extract system is exactly the kind of hazard that assessment is meant to catch. Cleaning the extract is not optional good manners; it is part of managing a known risk. When a fire officer carries out an audit, they will ask to see your post-clean verification records. If you cannot produce them, the exposure is real: enforcement notices, prosecution and personal liability all sit on the table.
Insurers have moved in the same direction. Many now require proof that extract ductwork is cleaned and inspected on a recognised schedule, and a claim traced back to a greasy, unmaintained duct can be reduced or refused. This is where the small access panel quietly earns its keep. Because the run could be opened, measured and photographed, the building had a dated record showing the system was found, addressed and scheduled for follow-up. That paper trail is the difference between due diligence and an argument you lose after the event.
TR19 Grease ties cleaning frequency to how hard the kitchen works, and it is worth knowing the bands so you can judge your own site honestly. Heavy use of roughly 12 to 16 hours a day points to cleaning every three months. Moderate use of 6 to 12 hours a day points to every six months. Light use of 2 to 6 hours a day points to every twelve months. These are starting points, not guarantees - a busy grill or wok station can push grease past the limit faster than the calendar suggests, which is exactly why measurement matters more than assumption.
The proof is as important as the clean. A compliant visit should leave you with a Post-Clean Verification report that records the date, lists the areas cleaned, shows the before-and-after condition with photographs taken from matching positions, and flags any section that could not be reached - with a clear recommendation to improve access. Deposit Thickness readings turn "it looks clean" into a number you can stand behind at 200 microns or below. That report is what you hand to an insurer, a fire officer or an environmental health inspector, and it is only ever as complete as the access allows.
The moral of our little story is not really about one panel. It is that access is the foundation everything else stands on - inspection, measurement, cleaning and proof. Get the openings right and a kitchen extract system becomes a manageable, provable, low-risk part of the building. Leave them out and you are trusting a hidden run of ductwork to look after itself, which grease never does.
Questions
An access panel is a small, sealed, reopenable opening in the wall of extract ductwork, fixed with quick-release catches and made from the same material as the duct. It matters because it is the only way to inspect, measure and clean the inside of a run. Without adequate panels, sections of duct stay hidden, and hidden grease is exactly what turns a minor kitchen flare-up into a building fire. TR19 Grease treats access as the foundation of a compliant system.
TR19 Grease guidance is that panels should let you reach and inspect the whole of the ductwork, positioned at intervals of roughly every two metres and at every bend or change of direction where grease collects. Panels should sit on the side of the duct where possible, with the top or underside used only as a last resort and sealed carefully. A single overlooked run without enough panels can leave a hazard completely invisible until an engineer manages to open it.
Under TR19 Grease, frequency follows how hard the kitchen works. Heavy use of about 12 to 16 hours a day points to cleaning every three months, moderate use of 6 to 12 hours to every six months, and light use of 2 to 6 hours to every twelve months. These are guides - a busy grill can exceed the acceptable grease level sooner, which is why a Deposit Thickness Test to measure against the 200 micron threshold is more reliable than the calendar alone.
You need a Post-Clean Verification report that records the date, lists every area cleaned, shows before-and-after photographs from matching positions, and notes any section that could not be reached along with a recommendation to improve access. Under the Regulatory Reform (Fire Safety) Order 2005 the responsible person must manage grease as a fire risk, and many insurers now require this documented evidence. Without it, a claim traced to a greasy duct can be reduced or refused.
Phoenix Duct Clean · by the numbers
Phoenix surveys and cleans kitchen and building ductwork to the TR19 standard - measured, cleaned and certificated, UK-wide.