Chemical cleaning becomes necessary when standard washing no longer restores the aircon’s cooling performance to a satisfactory level, when there is a persistent musty or moldy smell coming from the unit despite regular cleaning, or when visible mold and heavy grease buildup on the evaporator coil cannot be removed with water alone. In the Philippine climate where high humidity accelerates mold growth inside aircon units, chemical cleaning is often warranted every six to twelve months for units in daily use, particularly in areas with poor ventilation or high dust levels. If the unit has not been cleaned for more than a year, chemical cleaning is almost always the appropriate choice over a standard wash to properly restore its condition.