Acid mist, commonly referring to misty acidic substances. The particles of acid mist in the air are very small, smaller than those of water mist, and more humid than smoke, lying between smoke and water mist, and possesses strong corrosiveness. Most of them originate from sulfur oxides and nitrogen oxides emitted during the combustion of fossil fuels, with some also coming from vehicle exhausts (mainly nitrogen oxides). The main methods to control acid mist emissions include liquid absorption, solid adsorption, filtration, electrostatic mist removal, mechanical mist removal, and covering methods.