DESC: Hoover E7720 Silent Air 2000 Air Purifier - Enjoy the difference between filtering your air and purifying it! Virtually Silent, economical way to purify the air Designed for around-the-clock use Electrostatic technology traps small contaminants HEPA filters can miss. Hoover SilentAir Purifier works without noisy fans or motors. Its electrostatic design sends out safe, silent, invisible negatively charged ions that attach themselves to airborne irritants, like animal dander, allergens, dust, and smoke.