A fan comprises a rotatable hub, a plurality of fan blades coupled with the hub, and a plurality of air fences coupled with the fan blades. Each fan blade has a free end and an opposite end secured to the hub. The air fences are positioned at selected locations along the length of the fan blades, between the ends of the fan blades. Each air fence includes a fin, which may extend upwardly or downwardly from the fan blade. Each air fence may be formed of a resilient material and may be configured to allow the air fence to be snapped onto a fan blade. Each air fence may define an opening through which a fan blade may be inserted. One or more surfaces of the air fence may be contoured to complement a surface contour of an airfoil shaped fan blade.