Standard replacement filter for the Alen BreatheSmart Fit50 Air Purifier. Ideal for dust and allergen removal. The Alen BreatheSmart HEPA-Pure Filter combines two layers of filter technology to purify and freshen the air in your home. Polluted air first passes through Alen's washable Pre-Filter to capture large particles, extending the life of the filter. In the second layer, air moves through a unique, electrostatically charged HEPA style material that attracts and captures dust, pollen, pet dander, mold spores and other airborne pollutants. We recommend replacing your filter every 6-12 months for severe concerns or when running your air purifier 24/7. Replace your filter every 12-18 months for light concerns or when running the air purifier only as needed. Alen replacement filter #FF50.