Signs & diagnostics
Speckles of grease creeping across the ceiling around the canopy are a map of escaped plume. They mark where greasy air is slipping past the canopy edge instead of being drawn in - which means capture has fallen and the extract is no longer doing the one job it is there for.
The short answer
Speckles of grease creeping across the ceiling around the canopy are a map of escaped plume. They mark where greasy air is slipping past the canopy edge instead of being drawn in - which means capture has fallen and the extract is no longer doing the one job it is there for.
The detail
The plume above a cooking line carries grease as a fine aerosol. When the canopy holds its capture velocity, that aerosol is drawn in and caught by the filters. When capture weakens, some of the plume rolls past the canopy edge, drifts on the room's air currents, and deposits its grease on the nearest cool surface - often the ceiling around the canopy.
So ceiling speckling is not a separate cleaning chore - it is evidence. It tells you the extract is under-capturing, and it even shows you roughly where the plume is escaping, since the pattern tends to spread from the edges the canopy is failing to control.
The cause is usually the familiar one. Grease loads the baffle filters and duct, resistance rises, the fan moves less air, and capture velocity at the canopy face drops below what is needed to grab the plume. The grease that used to be caught inside the system now settles on the ceiling instead.
Weak make-up air can worsen it. A kitchen running negative pulls uncontrolled air across the space, disturbing the plume and pushing more of it out of the canopy's reach, which spreads the deposits further from the cooking line than you might expect.
What it means for you
The clean fixes the cause - restoring the filters, plenum and duct to TR19 Grease condition brings back the airflow and capture, so the plume is grabbed at source again and the overhead deposits stop growing. Wiping the ceiling without cleaning the system just resets the canvas for more.
The spread also flags whether more than grease is involved. If deposits persist after a verified clean, the canopy may not cover the equipment properly, the fan may be undersized, or make-up air may be inadequate - all of which let the plume escape regardless of how clean the system is.
Phoenix Duct Clean restores the airflow that keeps grease inside the system and measures the result, so the ceiling stops collecting the plume - and any remaining escape points to a design issue worth addressing.
The service behind the guide
Sibling guides
What a stale grease smell means · Spotting a badly done clean · Stadium and event kitchen extraction
Questions
Because the canopy is no longer capturing the whole plume. When airflow falls, capture velocity drops and some of the greasy air escapes the canopy edge, drifts on room currents and settles on the nearest cool surface, which is usually the ceiling around the canopy.
Usually, yes. The lost capture that lets grease reach the ceiling is generally caused by grease loading the filters and duct and stealing airflow. So overhead speckling is a good reason to inspect and measure the system, not just to redecorate.
If lost capture from grease is the cause, restoring the system to TR19 condition brings back the airflow and the plume is caught at source again, so the deposits stop growing. If they persist after a clean, the canopy fit, fan size or make-up air needs attention.
Grease deposits are combustible wherever they collect, and grease overhead near heat sources is not ideal, but the larger fire concern is the loaded ductwork behind the lost capture. Both are addressed by cleaning the system and reducing the grease load.
Yes. A kitchen running negative because make-up air is below around 85 percent of the extract rate pulls uncontrolled air across the space, disturbing the plume and carrying escaped grease further from the cooking line than lost capture alone would.
Phoenix Duct Clean · by the numbers
It marks lost capture. Book a clean to restore the airflow that keeps grease in the system.