Airflow fading over a kitchen line: grease-bound fins

This unit runs above a kitchen line for most of the trading day, in air carrying oil mist. Under that load the argument flips. Cleaning in place stops being enough long before the unit stops working.

By Team Snowflake | Reviewed 25 Jul 2026

Case summary

Midea Cassette15 years oldF&BOutram, Singapore

Concern: Previous servicing had been surface cleaning on a quarterly cycle, and each round returned less airflow than the one before it.
Found: Hardened cooking grease bound through the full fin depth and packed into the blower wheel, past what surface washing can lift
Key check: Dropped the ceiling panel and shone a torch through the fin block, which showed no light passing between the fins at any point
Result: Airflow came back to full throw across the counter and stayed there. Overhaul cycles were set to run twice a year for this unit, with light cleaning in between to slow the rebuild. Nothing was replaced, and no part had failed.

What we were told

Airflow over the service counter had been thinning out for the past year. Quarterly cleaning brought it back briefly, then it dropped away again faster each round. Staff had started pointing fans at the counter during lunch service. Cooling itself still felt present, just not reaching far enough into the room.

What we checked

Shortening gaps between cleans is the signal worth reading here. Airflow that keeps returning and then leaving is a deposit problem, not a fan problem. When each service buys less time than the last, the cleaning is reaching a shrinking share of the deposit. We dropped the ceiling panel to look at the fin block from behind rather than judging it from the grille face.

A torch held against one face of the fin block showed no light coming through the other side.
The blower wheel blades were rounded over with a brown crust, so each blade moved less air than its shape intends.
Surface fins wiped clean easily. The layer underneath was hard, dry to the touch, and would not shift under a fingernail.

What we found

Cooking vapour carries oil that stays airborne well past the hood. It lands on the coldest surface in the room, which is the fin face, and it does not stay soft. Each cooling cycle bakes a thin layer onto the last one until the deposit behaves like a coating rather than a soil. Foam washing lifts whatever is still greasy on top. Everything cured underneath stays put, which is why the clear window kept shrinking.

What fixed it

Here the full overhaul was the correct scope. The unit came down, the coil block and blower wheel were separated out, and both went through alkaline soaking rather than a surface pass. The drain pan and pipe were stripped and flushed. That level of work is justified when the deposit is cured through the depth, which is exactly what a kitchen produces and a bedroom does not.

Outcome

Airflow came back to full throw across the counter and stayed there. Overhaul cycles were set to run twice a year for this unit, with light cleaning in between to slow the rebuild. Nothing was replaced, and no part had failed.

What this case teaches us

Grease cures into a coating, dust only sits

Oil mist condenses on cold fins and cures into a varnish that water and foam slide over.
A kitchen unit reaches the strip-down threshold in a fraction of the time a home unit takes.
If airflow drops again within weeks of a clean, the buildup is deeper than the cleaning reached.

Questions this case answers

Is a full chemical overhaul ever actually necessary, or is it always an upsell?

It is necessary when the deposit has cured through the fin depth, which is what a kitchen produces. On this Outram shophouse cassette a torch pressed to one face of the fin block put nothing through the far side. Surface fins wiped clean, but the layer beneath was hard and would not lift under a fingernail.

Airflow drops again soon after every cleaning, what does that mean?

A shrinking clear window means the cleaning is reaching less of the deposit each round. Oil mist from the line lands on the cold fin face and bakes into a varnish, layer on layer, and foam slides over it. Quarterly surface cleaning here kept returning airflow briefly and then losing it sooner, which was the signal.

How often should a kitchen aircon be serviced compared to one at home?

Far more often. A unit over a cooking line reaches the strip-down threshold in a fraction of the time a bedroom unit takes, because it is pulling oil-laden air all trading day. For this cassette we set overhaul cycles twice a year with light cleaning in between to slow how fast the deposit rebuilds.

Do I need to replace the blower wheel if grease has built up on it?

Nothing was replaced on this unit and no component had failed. The blower wheel blades had rounded off under a brown crust, losing the edge profile that throws air, but the wheel itself was sound. Once the coil block and the wheel had been soaked out, airflow returned to full throw across the counter.

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