A robot with improved cleanliness for use in a clean environment is disclosed, having a uniform flow through the open interface between the clean environment and the interior of the robot housing, passing the particle generation area to an exhaust port, keeping the particles from the clean environment. The uniform flow reduces or eliminates the back flow, and further allows the scalability of the open interface to prevent particles generated from moving mechanisms within the robot housing to contaminate the clean environment. The uniform flow can be established by designing the flow dynamic, centering the exhaust port, or by restricting the flow along the elongated slot, for example, by uniformly restricting the flow along the elongated slot, or by implementing a restrictor along the elongated slot.