This technique has found a variety of applications although its use is not common. Rock drilling dust has been controlled by using hollow core drill steel with suitable exhaust holes in the drill bits. Air is exhausted either by a multi-stage turbine of the size generally used in industrial vacuum cleaners or, in the case of one manufacturer, by the exhaust air from the pneumatic tool which operates a Venturi to withdraw air from the drill. Some applications use flexible connections to a central vacuum system to aid in the control of graphite dust at conventional machining operations. One-to two-inch diameter flexible hose was used with simple exhaust hoods mounted directly at the cutting tool. In a similar application for the machining of beryllium, a central vacuum system utilizing 1.5-inch I.D. flexible hoses was employed. The exhaust hoods were made of Lucite or transparent material and were tailor-made to surround the cutting tools and much of the work. Exhaust flow rates vary from 120-150 cfm with inlet velocities of 11,000-14,000 fpm. In another application, a portable orbital sanding machine has been fitted with a small exhaust duct surrounding the edge of the plate. A fitting has been provided to connect this to the flexible hose of a standard domestic vacuum cleaner.