Electrostatic precipitator, also called electrostatic air cleaner, is a device that uses an electric charge to remove certain impurities—either solid particles or liquid droplets—from the air or other gases in smokestacks and other flues. The precipitator functions by applying energy only to the particulate matter being collected without significantly impeding the flow of gases. Originally designed for the recovery of valuable industrial-process materials, electrostatic precipitators are used for air pollution control, particularly for removing particles from waste gases at industrial facilities and power-generating stations. Precipitators function by electrostatically charging particles in the gas stream. The charged particles are attracted to and deposited on plates or other collection devices. The treated air then passes out of the precipitator and through a stack to the atmosphere. When enough particles have accumulated on the collection devices, they are shaken off the collectors by mechanical rappers. The particulates, which can be either wet or dry, fall into a hopper at the bottom of the unit, and a conveyor system transports them away for disposal or recycling.