Canopy, filters & fan
A full kitchen extraction clean covers the whole grease path - the canopy, the filters, the plenum behind them, the ductwork and the extract fan - not just the visible surfaces. TR19 Grease treats the system as one connected route for grease and fire, and measures the result rather than trusting the eye.
The short answer
A full kitchen extraction clean covers the whole grease path - the canopy, the filters, the plenum behind them, the ductwork and the extract fan - not just the visible surfaces. TR19 Grease treats the system as one connected route for grease and fire, and measures the result rather than trusting the eye.
The detail
Grease-laden air leaves the cooktop and travels a fixed route: up into the canopy, through the grease filters, into the plenum chamber directly behind them, along the ductwork, through the extract fan and out at the discharge. Every one of those stages collects grease, so a clean that stops at the visible canopy face leaves most of the system untouched. Extraction cleaning, done properly, follows that route from end to end.
The canopy and its filters are only the entry point. Behind the filters sits the plenum, the first hidden space where grease settles, and beyond it the ductwork carries deposits deep into the building. The extract fan, whether roof-mounted or in-line, collects grease on its blades and housing. TR19 Grease, the BESA specification for managing fire risk from grease accumulation, treats all of it as one system because a fire in a duct travels the whole length.
This is why a compliant clean is verified by measurement, not appearance. TR19 Grease sets a mean grease deposit limit of 200 microns between cleans, flags any area at 500 microns or more for immediate attention, and requires deposits to be brought below 50 microns after cleaning. Those levels are checked with a Wet Film Thickness Test for soft grease or a Deposit Thickness Test for harder, carbonised deposits, at set points from the plenum behind the filters right through to the discharge duct.
Access is what makes the whole path reachable. DW/172, the design specification these systems should be built to, calls for access panels of sufficient number, quality and size so that every internal surface can be inspected and cleaned. Where panels are missing or too far apart, sections of duct simply cannot be reached, and a clean that cannot reach a surface cannot verify it. Good access is the difference between a full clean and a partial one dressed up as complete.
What it means for you
Knowing what a full clean covers lets you tell a real one from a token one. A contractor who cleans only the canopy and filters and issues a certificate has documented a fraction of the system while leaving the ductwork and fan - the parts that carry a fire through the building - untouched. When you understand the whole path, you can ask the questions that separate a genuine TR19 clean from a quick wipe with paperwork attached.
It also matters for your insurance. TR19 Grease is recognised by the Association of British Insurers, and a buildings or contents policy can be treated as invalid if a kitchen cannot show its extraction system has been cleaned and verified across its full extent. A post-clean verification report, with before-and-after photographs and thickness measurements, is the evidence that the whole system was addressed rather than just the parts on show.
Across this cluster we take each part of that path in turn - the filter types and how they change the clean, the plenum and gutters, the fan, and the specialist canopies that behave differently. Read together they explain why extraction cleaning is a system job, and why the canopy looking clean tells you very little about the state of everything behind it.
The service behind the guide
Sibling guides
Why filter type changes the clean · How baffle filters work · How often to clean your system
Questions
The whole grease path: the canopy, the grease filters, the plenum chamber behind them, the ductwork, the extract fan and the discharge. A clean limited to the visible canopy leaves most of the system untouched.
No. The canopy and filters are the entry point. The plenum, ductwork and fan all collect grease and carry fire risk, so TR19 Grease treats the system as one connected route that must be cleaned and verified throughout.
By measurement. Deposits are checked with a Wet Film Thickness Test or Deposit Thickness Test at set points and must be brought below 50 microns, recorded in a post-clean verification report with photographs.
TR19 Grease sets a mean of 200 microns between cleans and flags any area at 500 microns or more for immediate attention. After cleaning, deposits should be below 50 microns.
Because a surface that cannot be reached cannot be cleaned or verified. DW/172 calls for enough access panels of the right size and position so every internal surface can be inspected and cleaned.
Phoenix Duct Clean · by the numbers
We clean the whole path - canopy, filters, plenum, ductwork and fan - and verify the result to TR19 Grease. Call or email for a clear quote and a certificate you can show your insurer.