The disclosed electrostatic precipitator cartridge for a tower air cleaner in accord with the present invention is low-cost, because it is constructed of injected molded plastics material and stamped and extruded metal components. It is easy to clean, not only because it's constitutive metal parts and plastic components are machine washable but also because the cartridge as a whole is machine washable, the pieces and components are designed and arranged to prevent intracartridge fluid buildup or retention after washing, thereby eliminating any electrical shorting or arcing or other undesirable phenomena resulting therefrom that could interfere with the operation of the electrostatic filter cartridge. It is mechanically stable and has high particulate collection efficiency because it's ionizer bars have a predetermined preferably air foil shape that provides improved ionization efficiency and that imparts improved torsion stability rendering it possible to provide taller electrostatic filter cartridges and/or greater cleaning power.