Signs & diagnostics
Paying for a clean is no guarantee the whole system was cleaned. If grease returns fast, panels look untouched or no verification report arrived, the last clean may have stopped short of the concealed run.
The short answer
Not every duct clean reaches the whole system. Some stop at the canopy and filters - the visible, easy-to-reach parts - and leave the concealed ductwork, the rises and the fan much as they were. That is a partial clean, and it leaves the fire risk largely in place while giving the impression the job is done. The telltale signs are worth knowing: grease returning far faster than it should, access panels that look untouched, stretches of duct with no access at all, and an absence of the verification paperwork that proves the work was genuinely completed.
The signs in the system itself
The clearest physical sign is grease coming back quickly. A properly cleaned system is verified down to bare metal - under fifty microns - so it should take the normal interval to load up again. If heavy grease, smells or drips reappear within weeks, the likelihood is that the deposits were never fully removed; the surface was cleaned but the concealed run was not. A clean that does not last was probably not complete.
Look at the access panels, too. If they show no sign of having been opened - fixings undisturbed, seals intact, grease still visible inside - then the ductwork behind them was not reached. TR19 Grease relies on panels at regular intervals, a minimum of every two metres and at direction changes, so the whole run can be cleaned; panels that were clearly never opened, or stretches of duct with no panels at all, mean there are lengths nobody cleaned. A canopy that gleams above a duct that was never entered is the signature of a partial job.
The signs in the paperwork
A complete, compliant clean produces evidence, and the absence of that evidence is itself a telltale sign. Under TR19 Grease, a clean should generate a post-clean verification report with before-and-after photographs and deposit measurements confirming the surfaces are below fifty microns, and the work should be registered so a certificate can be issued recording whether the system was fully or partially cleaned. If you received none of this - no report, no photos, no certificate - there is nothing to show what was actually done.
That paperwork gap matters beyond tidiness. The verification report is what an insurer or fire risk assessor relies on as proof the system was cleaned to standard; without it, you may be treated as though the clean never happened. And a certificate that records a partial clean is itself a flag - it is honest about the fact that part of the system was left, which is useful to know but not the same as a full clean. When the evidence is missing or says partial, the system has not been fully dealt with.
What to do about it
If the signs suggest a partial clean, the answer is to establish what was actually cleaned and deal with the rest. A survey checks the concealed run and the fan, measures the grease that remains and shows where the last clean stopped short - so the parts that were missed can be cleaned to standard. This time the work is verified and documented, giving you a report and certificate that prove the whole system is clean, not just the visible steel.
Questions
A properly cleaned system is verified to bare metal, under fifty microns, so it should take the normal cleaning interval to load up again. If heavy grease, smells or drips return within weeks, that strongly suggests the deposits were never fully removed and the clean was partial.
Look at the fixings and seals. Panels that were opened show disturbed fixings and fresh seals; panels with undisturbed fixings, intact old sealant and grease still visible inside were not reached - which means the ductwork behind them was not cleaned.
A complete TR19 Grease clean should produce a post-clean verification report with before-and-after photos and deposit measurements confirming surfaces below fifty microns, plus a certificate recording whether the system was fully or partially cleaned. No report and no certificate means there is nothing to prove what was done.
Yes. The verification report is what an insurer or fire risk assessor relies on as evidence the system was cleaned to standard. Without it, you may be treated as though the clean never happened - so a missing report is both a sign of an incomplete clean and a compliance problem in its own right.
Then there are stretches of ductwork that cannot be reached or cleaned, so any clean is necessarily partial. TR19 Grease calls for panels at least every two metres and at direction changes; where they are missing, adding them is usually the first step to being able to clean and verify the whole run.
Phoenix Duct Clean · by the numbers
We survey what was actually done, measure what is left and clean the whole run - with a verification report that proves the system is genuinely clean, not just the easy parts.