A:Answer As per the instructions on page 17 of the owner's manual for the LG 550 Sq. Ft. 12,000 BTU Smart Window Air Conditioner - White, Model # LW1217ERSM, bullet #7 CLEAN FILTER: 'Clean Filter' LED will light up to notify you your filter needs to be cleaned. After cleaning the filter, press "Temp ▲▼" together to turn off the 'Clean Filter' light. (Filter reset must be done from the unit's control panel not the remote control)...^IFV