Gas valves are used to handle and control the flow of gaseous media such as liquefied petroleum and natural gas. They are made of metal or plastic and vary in terms of valve size, pressure rating, number of ports, and flow. Connection types consist of bolt flanges, clamp flanges, union connections, tube fittings, butt welds, socket welds, and internal or external threads. Gas valves are used in a variety of applications and industries. For example, some devices are used in aerospace, agricultural, automotive, commercial, construction, cryogenic, fire service, food service, or flood control applications. Others are used in the food processing, irrigation, maritime, medical, mining, or semiconductor industries. High-purity gas valves are used to handle gases such as nitrogen, argon, oxygen, and hydrogen. Specialized gas valves are also used in oil and gas production, the pulp and paper industry, and power generation.