In India coal-fired power plants are equipped with electrostatic precipitators (ESP) to combat the suspended particulate matter emission from the stack. The efficiency of electro precipitator in removal of particulate matter is dependent upon the ability of the particulate matter to accept and release of electric charge. This characteristic of the particulate matter is generally referred to as ash resistivity. An exhaustive literature survey was undertaken to understand the resistivity problem. The resistivity is an electrochemical property and this paper describes the other aspect of ammonia that helps in agglomeration of the particles and enhances the collection efficiency of the electrostatic precipitators.