Chlorosulfonic acid is used to synthesize 2,4,5-trichlorobenzenesulfonyl chloride, an intermediate for the acaricide trichlorfon, and is also used in the synthesis of saccharin and sulfa drugs. It is also used as a sulfonating agent in the manufacture of detergents, ion exchange resins, plastics, dye intermediates, etc. In military applications, it is used as a smoke screen agent.