Our method of Axial Flow Fan design is based on data obtained from the combination of the blade element theory, model fan tests in a wind tunnel, and tests of full-scale fans in the field. The data are plotted as curves for fans of standard theory form, making the actual operation in designing the fan very short and simple. For the analysis or design of special blade which is not conforming to the standards, the modified blade element theory is used, with airfoil section characteristics, which give resultant powers and efficiencies checking the standard model data.