With a recent tend to take high interest in the environmental problem and the acquisition of ISO 14001 standard, the time has come to reconsider the present working environment. Especially, air pollution by metallic fume from the progress of cutting and welling is an unavoidable issue for labor health. For settling this matter, it is necessary to design a highly efficient ventilation system that is generally composed of large-scale equipments due to big capacity of the fabrication shop. However, the physical property and movement characteristic of the fume, which is composed by minute particles in different sizes, have not been grasped accurately even now. In this paper, for establishing efficient ventilation system to control the fume flow, the transportation characteristic of fumes is studied by assuming the fume as a turbulent buoyant gas-phase flow. Three-dimensional numerical simulation on a part of a fabrication shop in some cases are carried out using k -ε model and SIMPLE algorithm to investigate the tendency of forming stagnant fume areas where advection effect on turbulent gas flow is weak. Furthermore, laboratory experiments on fume diffusion, in which pigmented salt waters are used in quasi-two dimensional models of a fabrication shop under an appropriate similarity law, are executed. A two-dimensional numerical simulation is also made and the predicted fume flow shows considerably good agreement with the experimental observation.