Abstract: An object to be treated such as soil, burned fly ashes, or the like containing organic halides is introduced to a hermetically sealable thermal decomposition furnace 310 and heated under reduced pressure. Emitted gases of the object to be treated are treated so that the generation and recomposition of dioxins are supressed. A heated residue of the object to be treated is cooled after being purged with a purge gas which is organic halide-free and has no organic halide generating capacity. Thus, the concentration of organic halides remaining in the heated residue can be held to an extremely low level.

Abstract: An object to be treated such as soil, burned fly ashes, or the like containing organic halides is introduced to a hermetically sealable thermal decomposition furnace 310 and heated under reduced pressure. Emitted gases of the object to be treated are treated so that the generation and recomposition of dioxins are supressed. A heated residue of the object to be treated is cooled after being purged with a purge gas which is organic halide-free and has no organic halide generating capacity. Thus, the concentration of organic halides remaining in the heated residue can be held to an extremely low level.