Abstract: A housing includes a removable top cover and encloses a removable electrostatic precipitating unit formed by a tandem arrangement of two cells each including parallel spaced collecting plates preceded by interspaced particle charging wires or elements. An air circulating fan is enclosed within the housing and is driven by a low voltage two speed DC motor. A first converter provides for converting a high voltage AC power supply to the low voltage DC power supply for the fan, and a second converter provides for converting the low voltage DC power to a DC power supply of several thousand volts for operating the electrostatic precipitating unit. Means are also provided for by-passing the first converter and for operating the fan and the electrostatic precipitating unit from a low voltage DC power supply.