2,4,6-Trichlorophenol, also known as TCP, phenaclor, Dowicide 2S, Dowcide 2S, omal, is a chlorinated phenol that has been used as a fungicide, herbicide, insecticide, antiseptic, defoliant, and glue preservative. It is a clear to yellowish crystalline solid with a strong, phenolic odor. It decomposes on heating to produce toxic and corrosive fumes including hydrogen chloride and chlorine.