To achieve the best match of a fan’s aerodynamic performance to a given system, while providing the required cooling, a fan should be selected such that the operating point falls within the recommended operating zone on the fan performance curve. Often, the system resistance curve and the desired operating point is not known. A wise choice can be made by understanding the airflow required to provide the desired cooling effect, as well as some indication of system impedance; these are often gained from experience with similar systems or simulation work. As an indication, axial type fans are ideally suited to being used at 2/3 of the maximum flow capability, while motorized impellers are better suited for use at 1/2 of the maximum flow. These factors should be considered an approximate guide, as advanced aerodynamic design can modify the ideal working zone of either fan type.