Honeywell HFR11 Enviracaire Pure HEPA Permanent Replacement Filter Because of more energyefficient construction methods or inadequate ventilation, indoor air can be up to five times more polluted than outdoor air, according to the Environmental Protection Agency. Honeywell electronic air cleaners remove airborne particles, especially very small particles that can pass through standard furnace filters. An air cleaner may also provide some relief to individuals suffering from allergies or other respiratory problems, and should be part of an overall allergy treatment program. Honeywell's Enviracaire Elite F300 Electronic Air Cleaner captures up to 98 percent of particles three microns in size, including mold spores, cat dander and dust.