A fume hood comprised of first and second side walls, a back wall, a work surface, and a top wall, the walls and work surface defining a work area, an access opening for providing a user access to the work area, a movable sash member disposed for vertical movement across the access opening, and an anti-cocking drive mechanism mechanically coupling a drive motor to the movable sash member. The anti-cocking drive mechanism is comprised of a first and a second forward friction wheel, a first flexible coupling mechanically engaging, either directly or indirectly, the first forward friction wheel and a first rear friction wheel and coupled to the movable sash member on one end, a second flexible coupling mechanically engaging the second forward friction wheel and a second rear friction wheel and to the movable sash member on one end, and a drive shaft connecting the first components to the second components such that each are rotated simultaneously by the drive motor and the sash member is raised and lowered evenly on both sides.