Diagnostics & problems / Hidden grease
Grease does not settle where you can see it. It condenses out of the air in the places a daily clean is never designed to reach.
Out of sight, still there
When you cook, high heat turns fats into a fine, airborne mist. The extract system is meant to pull that mist away - but it does not vanish. It condenses onto the first cool surfaces it meets, and almost all of those are hidden. A gleaming cookline can sit directly beneath the heaviest grease in the building.
Knowing where it collects is how you tell a clean surface from a clean system.
The first hiding places
The grease starts accumulating the moment the mist enters the canopy. The plenum - the void behind the filters - catches what the filters miss, and metal baffle filters only stop a portion of airborne grease, so plenty carries through. From there it reaches the extract fan, where it cakes onto the blades and housing, throwing the fan out of balance and making it work harder. All of this sits inches from a spotless canopy face and is invisible without opening the system up.
None of it is reachable, or even visible, during a daily clean. A fan running out of balance also draws more power and wears its bearings faster, so the hidden grease costs you in energy and repairs long before it ever costs you in fire.
The worst of it
The real hazard is the ductwork carrying the extract to the outside. Grease condenses most heavily in the horizontal runs and at every bend, exactly where airflow slows, building a thick, flammable lining along metres of duct you never see. Because it is out of sight, it is easy to assume it is not there - which is precisely why grease duct fires so often start in kitchens that looked immaculate. TR19 Grease exists because that concealed lining is the single biggest fire hazard a commercial kitchen carries.
And closer to hand
It is not only the extract. Grease drifts and settles behind and beneath equipment, on top of units and wall cabinets, and across the ceiling above the line - all places a daily routine steps around. These are the spots an inspector checks precisely because operators do not.
So a spotless surface is necessary but not sufficient. Grease condenses out of the air where you cannot see it, so a clean-looking kitchen tells you nothing about the extract and the voids - and only a deep clean of the whole system reaches them.
Questions
Almost certainly, in the places you cannot see. Airborne grease condenses inside the canopy plenum, on the fan and along the duct run - all hidden from view. A clean surface says nothing about the system behind it.
Only some of it. Metal baffle filters stop a portion of airborne grease; the rest carries through into the plenum, fan and ductwork, where it builds up steadily between cleans.
In the ductwork - especially the horizontal runs and bends where airflow slows and grease condenses most heavily. That hidden lining is the leading cause of commercial kitchen fires.
No. It needs opening at access points, cleaning along its length and verifying - work that requires the right access and a qualified technician, not a surface wipe.
A professional clean comes with a verification report - before-and-after photographs and grease readings - so you have proof the parts you cannot see were cleaned, not just the parts you can.
Phoenix Duct Clean · by the numbers
We survey the whole system - canopy, duct run and fan - and clean out the grease a daily wipe never reaches, with a verification report. Ask us for a survey.