Phoenix Journal · Ductwork
Access panels are the difference between ductwork you can prove is clean and ductwork you simply hope is. Placed well at the design stage, they turn every future clean into a straightforward job rather than a running battle.
Access panels are one of those details that get decided in an afternoon on a drawing and then haunt a building for twenty years.
When they land in the right places, a cleaning crew can reach every run of ductwork, prove the whole system is clean, and be gone before the kitchen opens. When they don't, whole sections sit uninspected, grease builds where nobody can see it, and the first anyone hears of the problem is a failed report or, far worse, a fire. The frustrating part is that the cost of doing it properly at design stage is tiny next to the cost of cutting new openings into a live, insulated, grease-laden system later.
This guide walks through where access panels belong when you are laying out a commercial kitchen extract system, what the UK standards actually ask for, and the small decisions that make the difference between ductwork you can maintain and ductwork you can only worry about.
What the standards ask for
The habit that causes most trouble is designing the ductwork purely as a route for air and treating access as an afterthought. The standards flip that around. For kitchen extract, the reference document is BESA's TR19 Grease, the specification for fire risk management of grease accumulation, and it is written from the cleaner's point of view. It expects every internal surface of the system to be reachable, inspectable and returnable to a mean grease deposit of under 200 microns, measured with a deposit thickness test. If a stretch of duct cannot be reached, it cannot be cleaned, and a system that cannot be fully cleaned cannot be signed off as compliant.
That single principle drives everything else. TR19 Grease asks for access doors at a minimum of two metres apart along accessible ductwork, close enough that a technician can reach in by hand and physically clean the run between them. The older sheet metal specification, DW/144, sets the design rule that cleaning access openings should be provided at distances not exceeding three metres, and adds a detail that trips people up on site - fixings and supports must not sit within a metre of an access opening, or you simply cannot get the panel off. BS EN 15780, the European cleanliness standard, backs this up and points to EN 12097 for the location and spacing of access components. The numbers vary slightly between documents, but the intent is identical: no length of duct should ever be more than an arm's reach from an opening.
The awkward places
Even spacing along a straight run is the easy part. The panels that actually earn their keep are the ones at the awkward features, because that is exactly where grease settles and where a cleaning lance cannot see around a corner. Work through the system feature by feature and put an opening wherever the airflow has to change what it is doing.
At every bend or change of direction, grease drops out of the moving air and lines the inside of the turn, so you want an opening positioned to reach into that elbow. In-line components are the classic blind spots: fire dampers, attenuators, volume control dampers and any transition or reducer all need access on both sides, because you cannot clean through them and you cannot inspect what is hidden behind them. TR19 Grease is explicit that components like fire dampers and attenuators - which it would rather were not buried in an extract run at all, but which turn up constantly in practice - each need physical access to clean their intricate surfaces. Add panels at the base of every vertical riser, where grease runs down and pools, and at the fan and any plenum or filter housing.
Then there is orientation, which quietly decides whether a panel is a help or a hazard. Fit them on the side of the duct wherever you can. Top-mounted panels drop debris on the technician's face and encourage a poor seal; underside panels are worst of all, because any grease that seeps past a tired gasket runs straight out and drips onto whatever sits below - which in a kitchen means the food, the staff or an ignition source. If geometry forces a panel onto the top or underside, it has to be sealed properly and checked, not just fitted and forgotten. The panel itself should be the same material as the duct, typically stainless steel for a grease system, with a proper gasket and quick-release catches so a crew is not fighting rusted screws every visit. A sensible working size is an opening at least half the duct's smaller dimension, so an arm and a tool can actually get inside, and where a technician is expected to physically enter a larger duct the standard calls for two openings on that section, one to get in and one to get out.
It is also worth remembering that a leaky panel is not only a hygiene problem. Every badly sealed opening bleeds conditioned or extracted air, which makes the fans work harder and quietly adds to the running cost of the kitchen - one of the many ways a commercial kitchen loses energy without anyone noticing. Getting the seal right protects both the cleaning report and the electricity bill.
Designing for the whole life of the system
The most useful thing a designer can do is stop looking at the layout as an air path and mentally walk it as a cleaning route. Start at the canopy, follow the duct to the fan, and at every point ask a simple question - if I had a lance, a camera and a pair of gloves, could I reach and prove this surface is clean? Wherever the honest answer is no, that is where a panel goes. Do this on the drawing and the openings cost almost nothing. Do it after the system is insulated, running and coated in grease, and every new opening means hot works, downtime and a compromised duct wall.
Mark each access position on the record drawings and, ideally, label the panels physically once installed, so the next cleaning crew and the next fire risk assessor can find them without guessing. That paper trail is part of compliance too: TR19 Grease expects the post-clean report to show that the entire system was accessed and verified, and a well-documented set of panels is what makes that report defensible to an insurer after an incident. A system designed with cleaning in mind is cheaper to maintain, quicker to certify and far less likely to spring the kind of surprise that closes a kitchen. It is genuinely one of the highest-value decisions on the whole drawing, and it is usually made in minutes.
If you are unsure how your proposed layout will hold up in practice, the people who clean these systems for a living are the best sounding board - they can tell you exactly where the last job lost half a day to a missing panel.
Questions
TR19 Grease asks for access doors a minimum of two metres apart along accessible ductwork, so a technician can reach in and hand-clean the run between them. The sheet metal specification DW/144 sets the design rule that cleaning openings should be provided at intervals not exceeding three metres. On top of even spacing, you need extra panels at bends, risers and either side of in-line components, so the practical spacing is often tighter than the headline figure.
Fit them on the side of the duct wherever the layout allows. Top-mounted panels drop debris onto the technician and tend to seal poorly, while underside panels are the worst option because any grease that leaks past the gasket runs straight out onto whatever is below. If geometry forces a panel onto the top or underside, it must be sealed carefully and checked regularly rather than fitted and forgotten.
At design stage a panel is just a marked opening on a drawing and adds very little to the build cost. Adding one later means cutting into a live, insulated and grease-coated system, which involves hot works, downtime and a weakened duct wall. Planning the panels up front also guarantees the whole system can be cleaned and certified to TR19 Grease, which protects both your compliance report and your insurance position.
Phoenix Duct Clean · by the numbers
Phoenix surveys and cleans kitchen and building ductwork to the TR19 standard - measured, cleaned and certificated, UK-wide.