Abstract: Series experiments are performed in the typical small-scale Vertical Shaft Simulation Worktable in State Key Laboratory of Fire Science. Varying the side opening positions, the smoke temperatures in the vertical shaft are measured corresponding to each position. Thus, the influence of opening position to the chimney effect is demonstrated. Results show that the smoke flow pattern varies with the fire location and the shaft configuration. The smoke flow pattern in different shaft configurations is analyzed, including closed vertical shaft, open vertical shaft, vertical shaft with openings on the side below neutral plane, vertical shaft with openings on the side above neutral plane, and vertical shaft with openings on both sides above and below neutral plane. Thus the influence of opening positions to the vertical shaft is revealed.