Phoenix Journal · Ductwork
A certificate is not proof your ductwork was actually cleaned. Here is how to spot a corner-cutting kitchen extract contractor, read your verification report properly and put a poor job right.
Kitchen extract cleaning
You paid for a clean, you were handed a certificate, and on paper everything looks fine - but a folded sheet of A4 is not proof that grease was actually removed from the parts of your system that matter.
Kitchen extract cleaning is one of those jobs where the work happens out of sight, high in the ductwork and deep inside the canopy plenum, which makes it uncomfortably easy for a contractor to do a light surface wipe, print a certificate and drive away. Most operators only discover the shortfall much later - during a fire risk assessment, an insurance review, or worst of all a claim after a fire. This page walks you through how to spot a corner-cutting job, what your paperwork should really contain, and the concrete steps to put things right without simply paying twice.
The UK benchmark for this work is the BESA specification TR19® Grease, which governs fire risk management of grease build-up in commercial kitchen extraction. It is the document your insurer, your fire risk assessor and your environmental health officer will all reach for, so it is the yardstick you should judge any contractor against too. When a clean falls short, the warning signs tend to be consistent.
Start with the physical evidence, because grease does not hide well once you know where to look. Open an access panel yourself after the team has gone and run a gloved finger along the inside of the duct. A properly finished surface should feel clean metal, not tacky or filmed. Look specifically at the awkward places - the bends, the vertical risers, the fan housing and the plenum behind the filters - because those are exactly the spots a rushed crew skips. The phrase "cutting corners" is almost literal here: the corners and bends of ductwork trap the most flammable deposits and are the hardest to reach, so they are the first thing to be quietly left alone.
Then look at what was, or was not, opened up. TR19® Grease expects access panels at regular intervals along the ducting, broadly every 2 to 3 metres wherever the run allows, so that every internal surface can genuinely be reached and inspected. If your system has long sealed sections with no way in, or if the panels that exist show no sign of having been unscrewed, then large stretches of duct simply cannot have been cleaned to standard. A contractor who tells you a fully enclosed run was cleaned without adequate access is telling you something that is not physically possible.
That last point is the one operators most often overlook. A certificate on its own carries very little weight; certificates issued with vague wording or heavy caveats can be treated as worthless by an insurer after a fire, and the claim voided. What actually protects you is the evidence behind it.
TR19® Grease does not ask you to take anyone's word for it. It sets a measurable pass mark and a defined evidence pack, which is precisely why a genuine clean is easy to prove and a poor one is easy to expose. These are the numbers and facts worth knowing before you challenge a contractor.
The verification report - sometimes called a post-work verification report - is where all of this comes together. A report that stands up to scrutiny includes before-and-after photographs taken from the same fixed positions, pre- and post-clean deposit readings in microns, and a schematic or "as installed" drawing marking every access and test point used. Crucially, it must also highlight any sections that could not be reached, with a clear recommendation to install further access. Honesty about what was left uncleaned is a mark of a good contractor, not a failing; silence is the red flag.
It is also worth knowing who to trust and who to escalate to. Competent firms are listed on the Ventilation Hygiene Register, the UK's recognised scheme for evidencing this technical standard, and compliant reports feed a national BESA database that insurers and enforcing authorities can check. If a contractor cannot point to a GHT-qualified technician or a register listing, you have every reason to question the certificate they handed you.
Finding out you were short-changed is frustrating, but the path forward is straightforward if you take it in order. The goal is not just to vent - it is to end up with a system that is genuinely clean and a paper trail that will hold.
Prevention is far cheaper than repair here. A large part of avoiding this altogether comes down to the specification you agree at the outset and the frequency you commit to, which is why it pays to set up a written cleaning schedule with your contractor that names the standard, the test method and the evidence you expect every visit. It also helps to understand the wider picture of how air actually moves through your kitchen, because a system that is struggling to move air properly through the building often masks exactly the neglected ductwork a corner-cutting clean leaves behind.
Above all, treat the verification report - not the certificate - as the thing you are buying. If the measurements, photographs and drawing are not there, the job is not finished, whatever the invoice says.
Questions
No. A certificate on its own carries little weight, and one issued with vague wording or heavy caveats can be treated as worthless by an insurer after a fire. What actually protects you is the post-clean verification report behind it, containing before-and-after photographs, pre- and post-clean deposit readings in microns and a schematic of the system. Treat the report, not the certificate, as the thing you are paying for.
Open an access panel after the crew has left and run a gloved finger along the inside of the duct - it should feel like clean metal, not tacky or filmed. Look closely at bends, vertical risers, the fan housing and the plenum behind the filters, as these are the spots a rushed team skips. Undisturbed sealant or painted-over screws on the panels are a strong sign they were never opened.
Under BESA TR19 Grease, post-clean grease deposits should sit at or below 50 microns, confirmed by a Deposit Thickness Test or Wet Film Thickness Test. A genuine contractor records both a pre-clean and a post-clean reading so you can see the improvement. If no measurements appear in your paperwork, there is no evidence the standard was met.
Photograph the untouched panels and any visible grease, keep the certificate, and put your complaint in writing setting out what TR19 Grease requires. Ask the contractor to return and complete the work or issue a proper verification report at no extra cost. If you do not trust them, bring in a second, Ventilation Hygiene Register-listed firm to carry out an independent Deposit Thickness Test and document the true state of the system.
Phoenix Duct Clean · by the numbers
Phoenix surveys and cleans kitchen and building ductwork to the TR19 standard - measured, cleaned and certificated, UK-wide.