If the grease or active charcoal filter of your ventilation hood(s) is saturated, the red LED indicator will light up. Your filter should then be cleaned or replaced as soon as possible. You can individually adjust the factory-set service life of the filters: The grease filter saturation indicator can be programmed for 20, 30, 40 or 50 hours, the indicator for active charcoal filter replacement for 120, 180 or 240 hours.