This is the PCO Cell replacement for the WS C2000 unit only. This replacement PCO cell should be replaced between 12 to 18 months of daily operation. Simple unplug the unit and open the cover to unplug and replace the PCO cell. Do not touch the honeycomb matrix with bare hands to avoid oils from your skin getting the matrix dirty. Handle the metal frame with your hands to keep the PCO cell clean during installation.