Always turn the unit off and unplug the air purifier from power before replacing the filter. Turn the unit upside down, unscrew the base over and unwrap the washable particle filter from the HEPA filter. Discard the old HEPA filter and wrap the washable particle filter on the new HEPA filter. Insert them into the unit and screw the base cover back on. Hold the POWER button down for 5 seconds to reset the system. For more information, please read the Use & Care manual.