Home / Kitchen Extraction Cleaning / Guide
Extraction cleaning - measurement
A TR19 Grease clean is not judged by eye - it is judged by a number. Grease deposit thickness, measured against a defined threshold, is what turns looks clean into is clean. Here is how that measurement works and why it decides everything.
The short answer
TR19 Grease decides a pass by measuring grease deposit thickness, not by appearance. The standard treats a system as clean when the average deposit is at or below 0.05 mm - fifty microns. Readings are taken at representative points before and after cleaning, so the result is proven with figures rather than judged by eye. That measurement is what makes a TR19 Grease clean verifiable, and what your insurer and fire risk assessor rely on.
Why measure at all
Grease is the fuel in a kitchen extract fire, and the amount of it is what sets the risk - so the standard is built around measuring that amount rather than trusting appearances. A canopy can be wiped to a shine while the concealed ductwork behind it still carries a dangerous coating, and the eye cannot tell the difference. A number can.
That is why TR19 Grease is a measured standard. By fixing a threshold of deposit thickness and requiring readings against it, the standard replaces opinion with evidence: either the grease is below the level or it is not, and the figures say which. This is what makes a compliant clean something you can prove rather than assert.
The threshold
The number that decides it is 0.05 mm - fifty microns - of average grease deposit. At or below that, the system is considered clean to the standard; above it, cleaning is required. Fifty microns is a fine layer, which is the point: the threshold is set low because it is thin build-ups, accumulated across a whole concealed system, that carry the fire risk.
Because it is an average across representative points, the measurement reflects the state of the system as a whole rather than a single lucky or unlucky spot. That makes it a fair test of whether the whole run has genuinely been cleaned, not just the easy sections.
How it is measured
The measurement is taken at points chosen to represent the system - along the ductwork runs, in the risers, near the fan - both before cleaning and after. The pre-clean readings record the state the system was in; the post-clean readings prove it was brought down to or below the threshold. It is the pairing that matters: before establishes the problem, after proves it was solved.
Taking readings at representative points, rather than one convenient spot, is what stops the test being gamed. A clean that reached only the accessible sections would show that in the readings from the parts that were not reached - which is why an honest measurement schedule, and honest notes on anything inaccessible, are part of a proper result.
What the readings prove
The before-and-after figures are the heart of a TR19 Grease verification report, because they are what an insurer, fire risk assessor or inspector actually relies on. A statement that the system is clean means little on its own; a set of readings showing deposit brought from above the threshold to below it is proof. It converts the clean into the evidence your compliance and cover depend on.
This is also what distinguishes a measured, standard-compliant clean from a visual once-over. Two systems can look equally bright after cleaning; only the one with readings against the threshold can show it actually meets the standard. The measurement is the difference between looking done and being provably done.
What it means for you
The practical takeaway is simple: a TR19 Grease clean should come with measurements, and you should expect to see them. Before-and-after deposit readings against the 0.05 mm threshold, taken at representative points, with honest notes on anything inaccessible, are what a proper clean produces. A certificate that just says the work passed, with no figures behind it, is not a verified result.
So when you commission or check a clean, ask for the number. The readings are what make the difference between a system you hope is clean and one you can prove is - and proving it is the entire point of working to the standard.
Questions
By measuring grease deposit thickness, not by appearance. The standard treats a system as clean when the average deposit is at or below 0.05 mm - fifty microns - proven with readings taken before and after cleaning.
An average grease deposit of 0.05 mm, or fifty microns. At or below that the system is considered clean to the standard; above it, cleaning is required.
Because thin build-ups accumulated across a whole concealed system are what carry the fire risk. The low threshold reflects that grease, even in a fine layer, is combustible fuel.
At points chosen to represent the system - along the runs, in the risers, near the fan - before and after cleaning, and averaged, so the result reflects the whole system rather than one spot.
The before readings record the problem; the after readings prove it was brought to or below the threshold. The pairing is the evidence an insurer or fire risk assessor relies on.
The measurements - before-and-after deposit readings against the 0.05 mm threshold, with honest notes on anything inaccessible. A certificate with no figures is not a verified result.
We measure grease deposit before and after against the standard, so your TR19 Grease result is backed by figures.
