TR19 & standards
The bit you can see is the easy bit. TR19 Grease is about the ductwork you can't - all the way to the fan and discharge.
The short answer
Cleaning the canopy and filters is the part everyone sees, but TR19 Grease covers the entire path grease-laden air travels - canopy, plenum, ductwork, vertical risers, fan and discharge. Grease that builds up in the hidden ductwork is exactly where the fire risk sits, so a canopy-only clean leaves you non-compliant and potentially uninsured.
What 'the system' actually means
Every time the extract runs, grease-laden vapour is pulled off the cookline, through the filters, into the plenum behind the canopy, then along the ductwork - often up vertical risers, across roof voids, through the fan and out at the discharge. TR19 Grease treats all of it as one system, because grease is deposited along the whole route, not just at the hood.
The visible canopy and filters are the bit a kitchen team can wipe daily, and should. But the specialist clean the specification asks for is about everything downstream of that - the runs you cannot see without opening the ductwork up.
Where the real risk hides
The most dangerous grease is usually the grease nobody looks at: the inside of a vertical riser, a duct run above a false ceiling, the blades of the extract fan. These sections are warm, enclosed and directly in the path of any flame from the cookline - the classic route by which a small hob fire becomes a duct fire that travels through the building.
Reaching them needs proper access - panels or doors cut into the ductwork at intervals - which is why a contractor who only ever touches the canopy is not equipped to make you compliant. If large sections can't be reached, the honest outcome is a partial clean, recorded as partial, not a compliant one.
None of this makes daily cleaning pointless - it just puts it in its place. Wiping down the canopy, changing or degreasing the filters and clearing the plenum are jobs the kitchen team should do routinely, and they slow how fast grease reaches the ductwork. But they are the first line, not the whole defence. The reason the specification cares so much about the concealed run is fire behaviour: a flare-up on the cookline follows the airflow, and a greasy riser or duct is effectively a chimney lined with fuel. Clean the visible mouth of that chimney and leave the flue loaded, and you have treated the symptom everyone can see while the real hazard sits out of sight.
The limit
The catch is that a freshly wiped canopy looks reassuring while the ductwork above it stays loaded. On paper you might even hold a certificate - for a partial clean. After a fire, a loss adjuster will ask what was actually cleaned and measured, and a canopy-only history is a weak answer. Compliance means the whole accessible system is brought under the limit and evidenced, which is why access and full-system cleaning go together.
Questions
No. The canopy and filters are only the visible start. TR19 Grease covers the whole extract - plenum, ductwork, risers, fan and discharge - because grease builds up along the entire run and that is where fire spreads.
Risers, roof-void runs and the fan are enclosed, warm and directly in the path of a cookline flame. They hold the heaviest grease and are the route by which a small fire becomes a travelling duct fire.
At most as a partial clean, logged as partial on BESCA. That is not the same as full compliance, and the inaccessible or uncleaned sections should be recorded honestly.
Usually access. Without panels or doors into the ductwork, risers and concealed runs cannot be reached, cleaned or measured. Retrofitting access is often what makes full compliance possible.
Yes. Insurers and loss adjusters look at what was actually cleaned and measured. A record showing only canopy cleaning leaves the ductwork unproven, which can undermine a claim.
Phoenix Duct Clean · by the numbers
We survey the full run behind it - risers, ductwork and fan - and tell you honestly how much is uncleaned, then bring the whole system up to TR19 Grease.