Standard replacement filter for the Alen BreatheSmart 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. Alen replacement filter #BF35.