Diagnostics & problems
A greasy ceiling is not just untidy - it is a reading. It tells you how much grease is escaping the extract and loading the duct hidden above the panels.
The short answer
Grease on the ceiling above a cookline is grease the extract failed to catch. Whatever settled on the ceiling also settled in the ductwork hidden above it - and that is the part that starts fires. Wiping the ceiling clears the mark but not the message: your extraction is under-capturing and the duct is loading.
The mechanism
Frying, grilling and chargrilling throw a fine mist of fat into the air. The canopy and extract are meant to capture that grease-laden vapour and carry it out of the building. When they cannot keep up - filters overdue, extract rate down, canopy too small for the cooking underneath it - the surplus does not vanish. It drifts up and condenses on the first cool surfaces it reaches, and the ceiling directly above the line is one of the first.
So a greasy ceiling is not a housekeeping oversight. It is a reading. It tells you how much aerosolised grease is escaping capture, and by extension how hard your extraction is having to work and how much is getting past it. The film you can see on the ceiling is a proxy for the film you cannot see in the duct.
Why it matters
Kitchen extract ductwork is usually routed out of sight - above false-ceiling panels, through roof voids, up external walls. That is exactly why grease in it is underestimated: no one sees it accumulate. The same uncaptured grease that dulled your ceiling is caking those hidden runs, and grease in the extract system is behind the large majority of serious commercial kitchen fires. If it ignites, the duct becomes a chimney that carries flame through the building.
Under TR19 Grease, the standard set by BESA, deposit thickness is measured through the system and a heavy build-up is treated as a high fire risk requiring immediate cleaning. Insurers commonly tie cover to that regime. A greasy ceiling is a free, visible early warning that a survey of the concealed ductwork is overdue.
The limit
Wiping the ceiling is necessary but it is not sufficient. The ceiling film is a symptom, and the thing it is pointing at - the grease coating the hidden duct and the extraction that let it get there - sits above the panels where a cloth never goes. Clean the ceiling and it looks solved; leave the duct and the capture problem, and the mark returns while the real risk keeps building. The right response is to read the sign and survey the system it is warning you about.
Questions
The ceiling film itself is a hygiene and appearance issue, but what it signals is a fire-safety one. Grease reaches the ceiling because the extract did not capture it, and the same uncaptured grease coats the hidden ductwork above - and grease in the extract is behind most serious kitchen fires. So the ceiling is best read as a warning that the concealed system needs checking, not just a surface to wipe.
The canopy and filters are meant to catch grease-laden vapour, but when they are overloaded or the extract rate is low, the surplus mist drifts past and condenses on the nearest cool surfaces - and the ceiling above the line is one of the first. A greasy ceiling therefore tells you how much grease is escaping capture, which is useful information about how your extraction is performing.
It is a strong indicator. The grease on the ceiling and the grease in the duct come from the same uncaptured vapour, and the duct is usually hidden above false-ceiling panels or in voids where build-up goes unnoticed. A visibly greasy ceiling is a good prompt to have the concealed ductwork surveyed against the TR19 Grease standard rather than assumed to be fine.
TR19 Grease is the BESA specification that insurers and fire risk assessors use to manage grease in commercial kitchen extract systems. It sets how the deposit is measured and how often the system should be cleaned based on that measurement. It is not a law in itself, but fire-safety duties and most insurance policies effectively require you to clean to a risk-based frequency and hold the certificate to prove it.
Only the visible part of it. Cleaning the ceiling removes the mark, but the grease coating the hidden duct and the extraction shortfall that let it escape are both still there above the panels. Left alone, the ceiling greases up again and the concealed risk keeps growing. The lasting fix is to survey and clean the extract system and address why so much grease is getting past the canopy.
Phoenix Duct Clean · by the numbers
We clean the canopy and surfaces the grease is landing on and survey the concealed ductwork the ceiling is warning about - inspected and cleaned to the TR19 Grease standard.