Cleaning Cassette and Ducted AC Units: What It Covers and What to Expect

A cassette is a roughly square unit mounted in the ceiling that blows air in several directions through a grille panel with a filter at its center. Above the panel, inside the ceiling, sit the fan, coil, condensate tray and, in some models, a drain pump.

Access is normally by opening the panel and removing the filter, and sometimes lowering the panel carefully to reach the coil. Since it hangs overhead, dust, cobwebs and light cooking grease in open kitchens can collect around the grille and show clearly.

With a ducted system the main unit sits above a false ceiling or in a service room, and air leaves through ducts to several outlets. The return filter is usually in a grille you can reach fairly easily, while the coil and fan need service doors opened.

The ducts collect dust over time, but cleaning them deeply needs equipment and assessment and may not be done on every visit. The most useful thing an owner can do between visits is clean the filter and the visible outlets.

Tell us the AC type, number of units, their position, ceiling height and whether there is an accessible false ceiling. Move furniture away or cover it if it sits under the unit, and make sure power to the unit can be isolated while work is under way.

After cleaning, run the AC and watch for cooling, absence of odors and dripping during the first days. If it does not improve, the problem may be technical, such as refrigerant, compressor or drain pump, which needs a refrigeration technician.

Clean the filter regularly when it can be reached safely, and wipe the grille and outlets with a dry cloth. Limit cooking fumes and construction dust near the unit, and on humid days let the fan run to dry the coil before switching off if your unit supports it.

For more on odor and water-leak signs in common units, see our other guides on the site.