Product review (4 stars): For health and comfort
This is a popular required filter for the Cool Mist humidifier, but has been out of stock on Amazon, so I'm pleased to finally be able to place my order.  It is important for filtering pollutants, so one breathes cleaner air and to protect the humidifier itself.  The filters were sent very quickly and were well packaged.  The length of time between filter changes is influenced by your environment and the water used.  Thankfully, the filter helps keep the humidifier cleaner longer, but the humidifier will still need cleaning by hand.  One may need a bacteriostat as well.  All of this does add up financially.  Cleaner, comfortably moist air, especially important during the heating season, is good for the person, their furniture, and for some pets.  Recommended.