If the grease or active charcoal filter of your Miele cooker hood is saturated, it is indicated by a lit-up red LED. 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.