A fan (200) includes a housing (201) defining a duct (202). A spindle (203) can be concentrically located about a central axis within the duct. One or more fan blades (205,206,207) extending radially from the spindle toward a surface of the duct. Each fan blade is pivotable about a radial axis (208) between a closed position (400) where the each fan blade is in contact with each adjacent fan blade and an axially displaced open position (300) where the each fan blade is physically separated from the each adjacent fan blade. This prevents recirculation of air if a fan should fail.