This is the four-stage air purifier that senses the level of pollution in a room and adjusts its three-speed fan speed accordingly to maintain optimal air quality. The unit’s color-changing sensor system (red = very dirty, purple = dirty, blue = clean) constantly monitors air quality and automatically boosts the fan’s speed when it detects airborne impurities. Its washable pre-filter traps dust and pet hair, while a second charcoal filter absorbs odors and harmful gases. Next, air passes through a True HEPA filter that captures 99.97% of particles as small as 0.3 microns, including allergy-provoking pollen, dust mites, mold, tobacco smoke, and pet dander. Finally, an internal ionizer freshens the air by releasing negatively charged ions that break down airborne bacteria and viruses, rendering them harmless. The device purifies up to a 326' sq. room with a Clean Air Delivery Rate (CADR) of 233/246/240 for smoke/pollen/dust. With a 1/4/8-hour timer, filter replacement indicator, and built-in carrying handle for easy transport between rooms. Carbon filter lasts 6 months, HEPA filter one year. 18 1/2" H x 16 3/4" W x 9 1/2" D. (15 1/2 lbs.)