Home / Kitchen Extraction Cleaning / Guide
Extraction cleaning - design and specification
Access panels are what let a kitchen extraction duct be cleaned inside - and where they go decides whether the whole system can ever be reached, or whether sections are left uncleanable for the life of the building. So their placement belongs in the design, not as an afterthought. Here is where to put access panels: along the runs at regular intervals, at every change of direction, and at the fan.
The short answer
Access panels should be placed so that every internal part of the ductwork can be reached for inspection and cleaning. In practice, that means panels at regular intervals along the straight runs - commonly cited as roughly every 2 metres for grease-extract ductwork - so no stretch of duct is beyond reach; a panel at every change of direction, because grease concentrates at bends and a bend blocks access along the duct from either side; and panels at the fan and any other component that must be reached, such as filter housings and any in-line equipment. The principle behind all of this is simple: there should be no section of the internal ductwork that no panel can reach. Getting the placement right at the design stage means the system can be properly cleaned throughout for its whole life - whereas panels left out or misplaced leave sections that can never be cleaned without cutting into the ducts later.
Why placement belongs in the design
Whether a kitchen extraction system can be properly cleaned is largely decided when the ductwork is designed and installed, by where the access panels go. Grease accumulates inside the ducts and has to be cleaned out from inside, through access panels; if the panels are not there, or are in the wrong places, sections of the duct cannot be reached, and cannot be cleaned, for as long as the system exists - short of cutting new openings into the ductwork later, which is disruptive and costly. So the cleanability of the system is effectively built in at design: good access placement makes it cleanable throughout; poor placement leaves it permanently part-cleanable.
This is why access-panel placement deserves proper thought at the design stage, rather than being an afterthought or left to chance. A designer who thinks about how the system will be cleaned, and places the panels so the whole internal run can be reached, gives the building an extraction system that can be kept clean and safe for its life. One who does not - who runs the ducts without planning the access - leaves a system with unreachable sections that will accumulate grease and fire risk unchecked, discovered later only when a survey or a problem reveals them. So the placement of access panels is a design decision with long consequences for fire safety and cleaning, worth getting right up front. The rest is about where, specifically, the panels need to go.
Along the straight runs
The first placement rule is that access panels should be provided along the straight runs of ductwork at regular intervals, so that no stretch of duct is beyond reach from a panel. Cleaning reaches a certain distance into a duct from each access opening; beyond that distance, the duct cannot be effectively cleaned. So panels need to be spaced closely enough that their reach overlaps and the whole run is covered. For grease-extract ductwork, the commonly cited interval is roughly every 2 metres - closer than for general ventilation ducting, because grease is heavy and stubborn and the reach into a greasy duct is limited. The exact spacing follows the guidance and the duct, but the principle is regular panels along every run.
This regular spacing is what ensures the long straight sections - which make up much of a system - are fully cleanable. Without it, the middle of a long run, far from any panel, becomes unreachable, and grease builds up there unchecked. So when designing the duct runs, panels should be planned in at the appropriate interval from the start, spaced so their cleaning reach covers the whole length. It is worth erring toward more access rather than less: a panel too many is a minor cost, while a gap with no access is a permanent uncleanable section. So along the straight runs, the rule is regular, closely-enough-spaced panels - commonly around every 2 metres for grease ducting - so the whole length can always be reached.
At every bend and the fan
Beyond the regular spacing along straight runs, panels are needed at specific points - and the two most important are every change of direction and the fan. A bend needs a panel for two reasons. First, a bend is where grease concentrates: the airflow changes direction, the grease cannot follow, and it drops out and builds up heavily right there - so a bend is a hot spot that particularly needs to be reachable for cleaning. Second, a bend blocks access along the duct: you cannot clean past a bend from a panel on the straight run, because the cleaning cannot turn the corner - so each bend effectively divides the duct, and each side of it needs its own access. For both reasons, a panel at or beside every bend is essential.
The fan, too, needs access, because grease accumulates on the fan blades and in the fan housing - the fan is one of the places grease builds up most, and it needs to be reached to be cleaned. So a panel giving access to the fan is a necessary part of the design. The same logic extends to any other component that must be reached: filter housings, any in-line equipment, and junctions where ducts meet. The general principle behind all these specific points is that anywhere grease concentrates, or anywhere that blocks access along the duct, needs its own panel. So the placement rules come down to: regular panels along the runs, plus a panel at every bend, at the fan, and at any component or junction - so that every part of the system can be reached, with no unreachable section left.
The principle: no unreachable section
All the specific rules - regular spacing, panels at bends, at the fan, at components - come back to one principle: there should be no section of the internal ductwork that no panel can reach. If you design the access so that a cleaner can get to every internal surface of the system, the system can be properly cleaned throughout, for its whole life. If any section is left with no access, that section is uncleanable, and will accumulate grease and fire risk indefinitely. So the test of good access design is simple: can every part of the inside be reached? Designing to satisfy that test is what gives the building a fully cleanable extraction system.
Getting this right at the design stage is far better than discovering the shortcomings later. Access panels planned into the design go in cheaply and neatly as the ducts are installed; panels added later, when a survey reveals unreachable sections, mean cutting into existing ductwork, which is disruptive, costly and never as clean as designing them in. So the sensible course is to place the access properly from the start - regular panels along the runs, at every bend, at the fan and at every component, satisfying the no-unreachable-section principle - so the system is fully cleanable from day one and stays that way. Access-panel placement is a small part of designing ductwork, but it decides whether the system can ever be kept clean and safe - which makes it well worth designing properly.
The takeaway
Access panels are what let ductwork be cleaned inside, so where they go decides whether the whole system can be reached or whether sections are left uncleanable for the building's life - which is why their placement belongs in the design. The rules: panels along the straight runs at regular intervals - commonly around every 2 metres for grease-extract ducting - so no stretch is beyond reach; a panel at every change of direction, because grease concentrates at bends and a bend blocks access along the duct; and panels at the fan and any other component that must be reached, such as filter housings and junctions. All of this serves one principle: no section of the internal ductwork should be left that no panel can reach.
Designing the access to satisfy that principle gives the building an extraction system that can be properly cleaned throughout, for its whole life - kept clean and safe rather than accumulating grease and fire risk in unreachable sections. And it is far better done at design, where panels go in cheaply and neatly, than discovered later when a survey reveals gaps and panels have to be cut into existing ducts. So place the access properly from the start: regular panels along the runs, at every bend, at the fan and at every component. Access-panel placement is a small part of the design, but it decides whether the system can ever be kept clean - which makes it worth getting right up front.
Questions
So that every internal part can be reached: along the straight runs at regular intervals - commonly around every 2 metres for grease-extract ducting; at every change of direction, because grease concentrates at bends and a bend blocks access along the duct; and at the fan and any other component that must be reached, such as filter housings and junctions. The principle is that no section should be left unreachable.
Because whether the system can be properly cleaned is decided by where the panels go, and fixing it later means cutting new openings into existing ductwork - disruptive and costly. Panels planned into the design go in cheaply and neatly as the ducts are installed, giving a fully cleanable system from day one; panels left out leave permanently uncleanable sections.
Closely enough that their cleaning reach overlaps and the whole run is covered - commonly cited as roughly every 2 metres for grease-extract ductwork, closer than for general ventilation because grease is heavy and stubborn and the reach into a greasy duct is limited. It is worth erring toward more access: a spare panel is a minor cost, an unreachable gap is permanent.
Two reasons. A bend is where grease concentrates - the airflow changes direction, the grease drops out and builds up heavily there - so it particularly needs to be reachable. And a bend blocks access along the duct, because cleaning cannot turn the corner from a panel on the straight run - so each side of a bend needs its own access. A panel at or beside every bend is essential.
Yes. Grease accumulates on the fan blades and in the housing - the fan is one of the places grease builds up most - so it needs a panel to be reached and cleaned. The same applies to any component that must be reached: filter housings, in-line equipment and junctions. Anywhere grease concentrates, or anywhere that blocks access along the duct, needs its own panel.
That there should be no section of the internal ductwork that no panel can reach. If every internal surface can be reached, the system can be properly cleaned for its whole life; if any section has no access, it is uncleanable and accumulates grease and fire risk indefinitely. The test of good access design is simply: can every part of the inside be reached?
Good access placement is what lets us clean the whole system - and where it is lacking, we can advise on the panels needed. Our cleaning reaches every part the access allows, back to a clean baseline.
