To decompose and reduce environmental contaminants such as chlorodibenzoxine by forming a combustion accelerating region in a region wherein a combustion fluid passes, and accelerating the combustion by making the combustion fluid pass the region.

A gas source is provided 103 to generate a burnable gas 101 as a combustion accelerator in order to burn a combustion fluid such as a combustion gas 82 or a waste gas 85 which is generated in a combustion device 100. A jetting member 104 is provided which jets the burnable gas 101 being generated in the gas source 103, to the combustion fluid in order to burn environmental contaminants in the fluid at a high temperature by which the contaminants can be decomposed. The burnable gas 101 is introduced to a hollow annular manifold section 106, and the burnable gas 101 is jetted as a combustion accelerator to the combustion fluid such as the waste gas 85, when plastic waste is incinerated, from the nozzle ports 108 of a plurality of jetting nozzles 109. By this constitution, the environmental contaminants in the combustion fluid are kept under a high temperature state (1,000-2,000°C), and the environmental contaminants in the waste gas 85 are thermally decomposed easily.