Properly maintaining the air purification system in your Sub-Zero refrigerator ensures that it will scrub the air of mold, viruses and bacteria - contaminants too small for conventional filters - and lessen the ethylene gas that hastens food spoilage. Your refrigerator will alert you when it is time to replace the cartridge. Authentic Sub-Zero Factory Part. Part number 7007067. Note: The Label is in the process of being changed. You may receive a unit that says "Air Purifier" or one that says "Pure Air". They are both genuine Sub-Zero parts.