The telltale signs your last duct clean was incomplete

Look for telltale signs: only the visible canopy and filters touched, no access panels used, no before-and-after photographs of the ductwork, a vague certificate, a suspiciously quick or cheap job, or persistent symptoms afterwards - any of which suggests the hidden duct was left. Because the parts that matter most (the internal ductwork and fan) are hidden, an incomplete clean can look done while leaving the hidden grease. The telltale signs it was incomplete: only the visible parts (canopy, filters) were touched, with no sign the ductwork and fan were; no access panels were used or fitted (so the inside of the duct can't have been reached); no before-and-after photographs of the internal ductwork (so no proof the inside was cleaned); a vague, generic certificate (with no specifics or photos); a suspiciously quick or cheap job (likely skipping the laborious hidden parts); and persistent symptoms after the clean (still smoky, weak airflow, roof staining - suggesting the real grease wasn't addressed). If these are present, the clean may have been incomplete. So check for these signs - especially the access and photos. So look for missing access, photos, detail and improvement. This is general guidance.

Because the parts that matter most - the internal ductwork and fan - are hidden, a clean of just the visible canopy and filters looks done from the kitchen, and a certificate reinforces the impression, while the hidden fire-risk grease is left. An incomplete clean looks complete because the important parts are out of sight. The internal ductwork and the fan - where the grease that matters for fire safety builds up - are hidden (inside the duct, up at the fan). So if a clean does only the visible parts (the canopy and filters, which are in the kitchen), it looks done from the kitchen, while the hidden grease (the real fire risk) is left in place. And if the clean comes with a certificate, you may reasonably assume it was thorough. So the visible signs (a clean canopy, a certificate) suggest a done job while the hidden reality (greasy ductwork and fan) is unseen. This is exactly why superficial cleans happen - they're quicker and cheaper for the cleaner and hard for the customer to detect. So you can't rely on the clean looking done, or on having a certificate - you need to check the telltale signs. So because the hidden fire-risk parts are out of sight. So the visible parts look done while the hidden grease remains. This is general guidance.

Yes - a proper clean documents the hidden internal ductwork with before-and-after photographs, since those surfaces are out of sight; no photographs of the internal ductwork means no proof the inside was actually cleaned. Yes - before-and-after photographs of the internal ductwork are a hallmark of a proper clean. Because the cleaned surfaces inside the duct are hidden, photographs (showing the internal surfaces before and after cleaning) are how the clean of those hidden parts is evidenced - they prove the unseen work was done. So a proper clean typically includes before-and-after photographs of the ductwork's internal surfaces as part of the documentation (alongside the certificate and report). If you got no photographs of the internal ductwork, there's no evidence the inside was cleaned - and a cleaner who genuinely cleaned the hidden duct would usually show it. So the absence of photographs is a telltale sign the hidden ductwork may not have been cleaned. When arranging a clean, expect before-and-after photographs of the ductwork - and treat their absence as a warning. So yes - and no photos means no proof of the hidden clean. So yes; expect before-and-after duct photos. This is general guidance.

Not necessarily - a certificate can be issued for a superficial clean, so it's not automatic proof; a proper certificate is specific and detailed with photos, while a vague, generic one is a warning that the clean may have been incomplete. No - a certificate doesn't automatically mean the clean was thorough. A certificate can be issued even for a superficial clean (a token certificate dressing up an incomplete job), so having a certificate isn't proof of a complete clean by itself. What matters is the quality of the certificate and the clean behind it. A proper certificate is specific and detailed: it says what was cleaned, to the TR19 Grease standard, for your particular system, with the extent and date, backed by before-and-after photographs. A vague, generic certificate - one that could apply to any job, with no specifics, extent or photos - is a warning sign that the clean (and certification) may not be substantial. So don't take a certificate at face value: check whether it's detailed and evidenced (specific to your system, with photographs), and be wary of a vague one (as covered in how to verify a TR19 cleaning certificate is genuine). So not necessarily - a vague certificate is a red flag. So no; check the certificate is detailed and evidenced. This is general guidance.

Get the system properly surveyed to see its real state - if the ductwork is still greasy, get it properly cleaned (whole system, to TR19 Grease, verified and photographed) - and in future use a contractor who evidences a complete clean. If the telltale signs suggest your last clean was incomplete, the response is to check and put it right. Get the system properly surveyed (or inspected): a good survey will reveal the actual state of the ductwork - whether it's still greasy despite the recent 'clean' - telling you whether the previous clean really did the hidden parts. If the survey shows the system is still grease-laden, get it properly cleaned: the whole system, to the TR19 Grease standard, verified by inspection and documented with before-and-after photographs and a detailed certificate - a genuinely complete clean addressing the hidden grease the last one left. And in future, use a contractor who evidences a complete clean (survey, access panels used and fitted, whole-system cleaning, and verification with photos and a detailed certificate). So verify the current state, put right any hidden grease, and choose a properly-evidencing cleaner next time. So survey it, clean it properly if greasy, and use a better cleaner. So get it checked and, if needed, properly re-cleaned. This is general guidance.

Use a contractor who runs a proper process and evidences it - survey, access panels used and fitted to reach the whole run, whole-system cleaning to TR19 Grease, and verification with before-and-after photographs and a detailed certificate; and check for those things. Avoiding an incomplete clean comes down to choosing a contractor who does (and proves) a complete clean, and checking for the evidence. Look for a cleaner who: surveys the system first (understanding it); ensures access to the whole run (using existing access panels and fitting more where needed - since the duct can only be cleaned if reached); cleans the whole system to the TR19 Grease standard (canopy, filters, the full ductwork run, and the fan - not just the visible parts); and verifies and documents the clean (with before-and-after photographs of the internal ductwork and a detailed, specific certificate). Then check you received those things - especially the access being used, the photographs of the hidden ductwork, and a detailed certificate. A contractor who works this way (as covered in how a duct clean actually runs) gives you a clean you can trust is complete. So use a properly-evidencing contractor and check for access, photos and a detailed certificate. So choose a cleaner who proves a complete clean. This is general guidance.