Honeywell 17000N Permanent Pure HEPA Quietcaire Air Purifier Reduces up to 99.4% of bacteria & germs New Permanent Lifetime True HEPA vacuumable filter QuietCare technology for ultra quiet operation 3 speeds with filter clean monitor Recommended for medium rooms This portable air cleaner is recommended for filtering the air in a closed room as large as 168 square feet (12 by 14 feet). As it continuously circulates a room's air--about six times per hour--it employs two filters to remove smoke, pollen, dust, animal dander, dust mites, molds, bacteria, viruses, and odors. Especially useful for asthmatics and allergy sufferers, the cleaner contains a true HEPA filter that is at least 99.97 percent effective at trapping extremely tiny particles (as small as 0.3 microns) while a prefilter reduces odors. Honeywell's IntelliCheck system permits monitoring the filters' lives. Each filter has a button. Pressing a button activates a light, which blinks or shines steadily. One blink indicates that the filter has lots of life remaining, two blinks means less life, three blinks means even less, and a steady light indicates the filter needs changing. The HEPA filter lasts one to three years; the prefilter, three months. Filter replacement is simple, and replacement filters can be ordered separately.