Using oval shaped cartridges, Downflo Oval 1 Series is available in compact Models 1-1, 2-2 (shown), and 3-3. Nanofiber filter media traps submicron dust particles on surface of filter, making dust easier to expel than conventional depth-loading cellulose, polyester, or blends. Cartridge's short stiff pleats will not collapse under pressure or trap dust. Dedicated integral power pack and control system allows plug-and-play operation from indoor electric outlet. Power pack is mounted internally at collector's base along with built-in silencer.