Orbit Calcium Inhibitor Filter for Outdoor Mist Cooling System. This filter protects your misting systems by preventing potentially clogging solid sediments from passing through the system. It filters particles as small as 5 microns, which is smaller than a human hair. Additionally, the filter coats smaller particulates with polyphosphates that enable easier passage through nozzles without forming blockages. Annual filter replacement is recommended and will prolong the life of mist nozzles.