Backward Inclined.  Performs at maximum efficiencies with relatively low tip speeds. Quiet operation, non-overloading characteristics, resulting in the smallest wheel diameter for given CFM. Good for corrosive environments. Easily made of special alloys. Higher pressure capability than the forward curve wheel. Efficiency is only slightly less than that of airfoil fans. Utilizes the same housing configuration as the airfoil design. Opening characteristics for this fan are similar to the airfoil fan. Blades are flat. Normally unstable left of peak pressure. Same heating, ventilating and air-conditioning applications as the airfoil fan. Also used in some industrial applications where the airfoil blade is not acceptable because of corrosive and/or erosion environment. 600-400,000 CFM single width; 1200-750,000 CFM double width. Static Pressures to 30".