The microwave plasma-torch and its application for decomposition of chemical warfare agent using a moderate microwave power are investigated. Decomposition of chemical warfare agents is demonstrated for phosgene (COCl/sub 2/) as a sample example. The main byproducts of phosgene decomposition are CO and Cl/sub 2/. The Cl/sub 2/ gas was completely converted to HCl by injecting NH/sub 3/ into the microwave plasma-torch as an additive gas. The HCl is, in turn, eliminated by passing the exhaust gas through a wet-scrubber. Detailed decomposition properties of phosgene by microwave plasma-torch at the atmospheric pressure are also investigated by making use of Fourier transform infrared, mass spectroscopy, and ion chromatography.