The gas commonly used for welding purposes is acetylene. Acetylene is often combined with oxygen in a process called oxy-acetylene welding, which produces a high-temperature flame that can melt and fuse metals. This method is widely utilized in various industries, from automotive repair to metal fabrication and artistic welding. The versatility and efficiency of acetylene make it a preferred choice for many welders, as it allows for precise control over the welding process. Additionally, safety precautions must be observed while handling acetylene due to its highly flammable nature.