MORE CLEAN AIR, FASTER: Only Blueair air purifiers use HEPASilent technology, Blue Pure 511 air purifier quickly cleans 16 m² small room in about 12.5 minutes or up to 38 m² space in 30 minutes. ULTRA QUIET: Quieter than a whisper at only 24 dB on low fan speed; Perfect for use in your bedroom for a good night sleep.