Blueair 400 series air purifiers are our most popular and quietest air purifiers. Available with electronics, the Blueair 400 Series provides exceptional air purification in rooms as large as 365 square feet, perfect for mid-sized bedrooms or office. Nice design and overall good performance. It comes with a 5 years limited warranty. It offers 4 fan speeds for maximum comfort. Like all Blueair models, the 400 Series features award-winning Swedish design, patented HEPASilent™ technology, whisper-silent operation, and by far the best warranty in the industry.