A chemical overhaul is the most comprehensive type of aircon cleaning available and involves fully disassembling the indoor unit so that each component, including the evaporator coil, blower fan, drainage tray, and casing, can be individually soaked, scrubbed, and rinsed with chemical cleaning agents before being reassembled and reinstalled. Unlike standard chemical cleaning where the solution is applied to the unit while it remains mounted on the wall, a chemical overhaul removes the unit completely to allow access to parts that are otherwise difficult or impossible to clean properly in place. This service is typically performed by experienced technicians and takes longer and costs more than a standard clean or chemical clean, but it restores heavily neglected units to near-original performance and is the most thorough way to address severe mold, persistent odors, or significantly reduced cooling efficiency.