TR19 & standards
The honest answer is: all of the run that carries grease. Here's what that stretches to, and why access decides whether you can prove it.
The short answer
TR19 Grease expects the entire grease-carrying extract cleaned and controlled under a 200-micron mean - from the canopy and filters, through the plenum and the full length of ductwork and risers, to the fan and the discharge point. In practice, how much you can actually clean and prove comes down to how much of that run you can reach.
The full extent of the system
Follow the air and you follow the grease. It starts at the canopy and filters over the cookline, collects in the plenum behind them, then travels the horizontal ductwork, up any vertical risers, through the extract fan and out at the discharge. Every one of those stages accumulates grease and is part of what the specification expects to be cleaned - the fan and discharge included, not just the runs closest to the kitchen.
Because grease loads fastest nearest the cookline and in the fan, some sections need attention more often than others, but the compliant baseline is the whole run controlled under the mean limit, evidenced with readings across it.
Where access sets the boundary
The practical limit on 'how much' is access. Ductwork hidden above ceilings, boxed into risers or buried in roof voids can only be cleaned and measured if there are access panels or doors at sensible intervals. Where they are missing, sections stay unreachable - and an honest report records them as inaccessible, producing a partial clean rather than a compliant one.
This is why good practice designs access in from the start, and why retrofitting panels is often the first step to getting an older system to full compliance. The question 'how much has to be cleaned' quietly becomes 'how much can you get to' - and closing that gap is usually straightforward once it is identified.
How often each stretch needs doing follows the same logic as how much. The canopy, filters and the first metres of duct load fastest and sit highest on the fire-risk list, so they may warrant more frequent attention and daily operator cleaning, while a long cool run further from the cookline fills more slowly. That is a scheduling question rather than a scope one: the scope is still the whole grease-carrying system, but a sensible programme cleans the heavy-loading sections often enough to keep the mean under the limit everywhere, and confirms it with readings each visit rather than trusting the calendar alone.
The limit
Aiming to clean everything is the right target, but the report has to reflect reality. A compliant outcome is the whole accessible system brought under the limit and the inaccessible parts flagged for remedial access - not a tidy certificate that quietly ignores the riser nobody could open. Read what was cleaned against what exists, and treat any gap as the next job rather than a pass.
Questions
All of the run that carries grease-laden air - canopy, filters, plenum, ductwork, risers, fan and discharge - controlled under a 200-micron mean. The whole accessible system, not just the sections near the kitchen.
Yes. The extract fan collects heavy grease and the discharge is part of the system. Both are included in what a compliant clean should cover and evidence.
Then it can't be cleaned or measured, and an honest report records it as inaccessible - a partial clean. Adding access panels or doors is what turns those sections into a compliant, full clean.
No. Grease loads fastest near the cookline and in the fan, so some sections may need more frequent attention, but the baseline is the whole run kept under the limit.
Because you can only clean and prove what you can reach. Access panels at sensible intervals are what make the concealed ductwork - often the highest risk - cleanable and verifiable.
Phoenix Duct Clean · by the numbers
We map the whole system - canopy to discharge - and tell you what has to be cleaned to comply, and where access needs adding to reach it.