Phoenix Journal · Ductwork
A signed invoice is not proof your ductwork was actually cleaned. Here is how to check a completed kitchen extract clean against the TR19 Grease standard, step by step.
Checking the job was done properly
Paying for a kitchen extract clean is one thing - proving it happened, and happened to standard, is another. A tidy invoice and a shiny canopy tell you almost nothing about the ductwork you cannot see, which is exactly where grease fires start and exactly where a weak contractor cuts corners.
Under the Regulatory Reform (Fire Safety) Order 2005 the responsible person - the owner, occupier or whoever has control of the premises - has to show that fire risk is being actively managed, and kitchen extract grease is one of the clearest risks on site. When an insurer, a fire safety officer or an environmental health inspector comes asking, the burden falls on you, not the contractor. So the audit is not busywork - it is how you turn a service you paid for into evidence you can stand behind. The benchmark everyone measures against is BESA's TR19® Grease specification, and this guide walks you through checking a completed job against it, step by step.
Work through these in order. Each one is a question you can answer with the paperwork and access in front of you - no specialist kit required beyond a torch and a willingness to open a panel.
Most disputes are not about outright fraud - they are about the gap between "we cleaned it" and "we cleaned it to standard, and here is the proof". TR19® Grease is deliberately specific because grease is measured, not judged by eye. The two numbers that matter are the post-clean ceiling of 50 microns and the mean average of 200 microns that a system is allowed to reach before its next scheduled clean falls due. A report that talks warmly about a "thorough deep clean" but never puts a figure against a location has told you how it felt, not what it achieved.
Photographs deserve the same scepticism. A genuine audit trail pairs each after shot with a before shot from the same spot, cross-referenced to a drawing of the system, so anyone can see which length of duct is being shown. Be wary of a report that leans on a handful of flattering close-ups of the easiest, most accessible metal while the risers, the fan housing and the far end of a long run never appear. What is not photographed is usually what was not cleaned.
Access is the quiet make-or-break. If the ductwork does not have enough hatches, large stretches simply cannot be reached, and a contractor may present a partial clean as a complete one. Where access is genuinely limited the honest move is to say so in writing and recommend that panels be fitted, rather than to imply the whole system was done. A report that flags access limitations openly is often more trustworthy than one that claims flawless coverage of an obviously awkward system.
Remember why the standard exists in the first place - it is fundamentally a fire risk and a health-and-safety obligation, not a box-ticking exercise. The same duty of care that makes you audit the clean sits alongside your wider responsibilities for a safe workplace.
None of this requires you to become a ventilation engineer. It requires you to ask for named locations, real measurements and matched photographs, and to open a couple of panels to check the paperwork against the metal. A reputable contractor will welcome that scrutiny, because it is exactly the evidence that protects both of you if a fire is ever traced back to the extract system.
If you take nothing else from this, take these figures with you to the next handover. They are the difference between a clean you hope was done and a clean you can prove was done - the standard your insurer, your fire officer and your environmental health inspector are all quietly measuring against.
Get the report, check it against the metal, and keep it on file. That habit turns every clean into evidence you can produce on demand - and it makes a weak contractor very easy to spot.
Questions
You should receive a full Post-Clean Verification Report, not just an invoice. It needs a written summary of the works, a system drawing showing what was cleaned, deposit thickness measurements against named locations, matched before-and-after photographs, and a dated hygiene certificate naming the qualified technician. If any of those elements is missing, the report is incomplete and may not hold up under insurance or fire-safety scrutiny.
Immediately after cleaning, TR19 Grease expects remaining grease deposits to be below 50 microns - roughly a tenth of the width of a business card. Over time a system is allowed to reach a mean average of 200 microns before its next scheduled clean falls due. These are measured figures from a Deposit Thickness Test or Wet Film Thickness Test, so look for real readings against locations rather than a general assurance that the system looks clean.
Yes, to a useful degree. Open two or three access panels at random and run a clean fingertip or a white wipe along the internal surface - grease coming away means that section was not properly done. Then match the report's photographs to a system drawing to confirm the hidden risers and fan housing were actually reached, not just the easy-to-see canopy. For definitive measurement you still rely on the technician's readings, but these spot checks quickly expose a weak clean.
Phoenix Duct Clean · by the numbers
Phoenix surveys and cleans kitchen and building ductwork to the TR19 standard - measured, cleaned and certificated, UK-wide.