A red filter replacement indicator appears on the air purifier when it is time to change filter, after 6 months of operation.
Press the center button down to reset the filter light indicator until the red light disappears. It usually takes 7-10 seconds and may take up to 30 seconds depending on the model.
On the Blue Auto air purifiers, the control panel will show 3 red lights if the air purifier is on Auto Mode, or 1 red light if another fan mode is selected: