The mixing of water and air has been studied in an agitated tank with narrow baffles. In such an agitated tank, the gas induction could be formed by the dual impellers operated above the critical impeller speed. Experimental parameters considered mere the impeller speed, the baffle width, the clearance between lower impeller and tank bottom, the impeller diameter, the space between two impellers and the liquid level. Dimensional analysis and data regression gave a good correlation between the mixing time, the tank geometry and operational variables. It was found that an increase in impeller speed reduced significantly the mixing time. Too much reduction of baffle width, a decrease in the impeller diameter or a raise of liquid level can increase the mixing time. However, after gas induction achieved, the clearance between the lower turbine and the tank bottom has no significant effect on the mixing time.