A blade (14) for a centrifugal flow fan (11) having forward curved blades. The blade has a boundary layer trip (21) on its pressure surface (14). The trip promotes the transition of the boundary layer from laminar to turbulent flow and enables the layer to remain attached to the pressure surface for a greater distance. The increased amount of attached flow enables greater fan efficiency and reduces fan radiated noise. The boundary layer trip may be of a variety of configurations.