The heavy-duty plasma torches are water cooled. They will fit in the same torch holders on automatic oxygen flame cutting machines. A water spray is sometimes used to surround the plasma to reduce smoke and noise. Worktables containing water, which is in contact with the underside of the metal being cut, also reduce noise and smoke. In some cases the water surface is above the top surface of the metal. The cutting speed versus material thickness for high-powered plasma arc cutting is shown in Figure 9-27. More information concerning this process variation is in the AWS -Recommended Practices for Plasma Arc Cutting.