Plasma-arc cutting (PAC) uses a high velocity jet of hot 27760°C (50,000° F) ionized gas to sever almost any conductive material--carbon, alloy, and stainless steel, and most nonferrous metals and alloys. The nozzle of a PAC torch constricts the plasma gas--air, oxygen, or nitrogen--to heat and ionize it. The process blasts out molten material along the cutting path at high speed, up to 255cm (100 inches) per minute through steel plate one inch thick or greater.
In addition to high energy radiation (both UV and visible) generated by PAC cutting, the intense heat of the arc creates substantial quantities of fumes and smoke from vaporizing metal in the kerf. Because most of these submicroscopic particles and gases are harmful, air filtration systems must be designed to handle both large and small particulate.
General Workplace Safety considers natural ventilation to be adequate if work space per welder is at least 285m³ (10,000 ft³) and if ceilings are at least 4.85 (16 feet) high with no barriers or partitions to impede airflow. Welding in smaller areas, or in any area where exposures cannot be kept below specified PELs (Personal Exposure Limits), requires forced ventilation. Beyond the minimum requirements, it is important to provide extra ventilation when welding materials contain large amounts of copper, lead, zinc, or beryllium.