Compliance & responsibility
A clean you cannot evidence is, for compliance purposes, a clean that did not happen. Here is exactly what to keep and for how long.
The short answer
Proving duct compliance is not about holding a single certificate - it is about holding a complete, dated record that a clean was carried out to TR19 Grease and verified. That means the certificate itself, the post-clean verification report that sits behind it, the before-and-after photographs, the grease readings, the contractor's recommendations and a note of any actions you took in response. Kept together and kept over time, those documents are what turn a claim of compliance into evidence of it.
What each record does
The TR19 certificate is the headline - it states the date, the location, the qualified technician and whether the clean was full or partial. The post-clean verification report is the substance behind it: the duct sections, hoods, filters and fans cleaned, the method used and the grease deposit readings taken by Deposit Thickness Test or Wet Film Thickness Test, confirming surfaces below the 50µm post-clean threshold.
The before-and-after photographs must be taken from matching positions so the improvement is genuinely comparable. The contractor's recommendations record any inaccessible areas, missing access panels or defects found - and, critically, you should keep a note of what you did about them, because acting on recommendations is part of the duty. Finally, the register entry: a compliant clean is logged on a national database an insurer or agency can check independently, which is the strongest proof of all.
How long to keep them
There is no single statutory retention period stamped on a duct certificate, but the practical answer is clear from who asks to see them. Food-safety and quality auditors routinely ask for the last three years of cleaning records, so a rolling three-year file is a sensible floor. Fire risk assessment records themselves must be retained and kept current under the Fire Safety Order and the Building Safety Act, and your cleaning history is the evidence that underpins them.
Keep the records where they can be produced quickly - on site or in an accessible digital system, ideally one that also flags the next clean before it falls due. When an environmental health officer, fire officer or insurer asks, the ability to produce a complete run of certificates and reports on the spot is what separates a business that is compliant from one that merely believes it is.
Keeping it effortless
The easiest compliance file is one you never have to assemble yourself. When the clean is done properly, the certificate, verification report, photographs and register entry are produced as part of the job and handed to you ready to file. That is how every clean we carry out is documented - so your three-year history builds itself, one visit at a time, and is always ready to produce.
Questions
The TR19 certificate, the post-clean verification report behind it, before-and-after photos from matched positions, the DTT or WFTT grease readings, the contractor's recommendations, a note of actions you took, and the entry on the national cleaning register.
Keep a rolling history. Auditors commonly ask for the last three years, so treat three years as a practical minimum, and retain the records that support your fire risk assessment for as long as it stands.
Not really. The certificate is the headline, but the verification report, photographs and grease readings are what make it defensible if an insurer or fire officer probes it. Keep the whole package together.
A document recording the sections cleaned, the method, before-and-after photos from matching positions, and the grease deposit readings confirming surfaces below 50µm - the evidence that the clean met TR19 Grease.
On site or in an accessible digital system so they can be produced immediately on request, ideally one that also reminds you when the next clean is due before it falls overdue.
Phoenix Duct Clean · by the numbers
Every clean we carry out is issued with a full verification report and a registered certificate you can file.