To obtain an inactivation in a wave brazing or a tin plating by arranging at the downstream side of a laminar flow wave and injecting a first inert gas at a specific range of flowing speed toward the flat surface of a laminar flow wave faced to this wave.

A dipping skirt 11 is firmly fitted to a chute system 10, and the chute system 10 is faced to one surface having two opening hole groups 15, 16 or a gas injector 12 having a wall 17. The opening hole groups 15, 16 are positioned so as to guide a first gas injection toward the flat surface of the laminar flowing wave 8B and a second gas injection toward the dipping skirt 11 respectively The opening hole groups 15, 16 have necessary size to obtain the gas flowing speed of 0.5-30m/s, desirably 0.5-10m/s from the opening holes. By this constitution, at the time of passing through a board, the remained oxygen content having only tens of ppm can be obtd. The gas from the outer part is supplied into a porous tube 14 in the inner part of the gas injector 12 to keep the system to the inert atmosphere through the opening hole parts 15, 16.