Which materials can be used to make pipes in gas systems?

The correct choice highlights the various materials that are approved for use in gas piping systems, which includes iron, steel, copper, brass, aluminum, and plastic. These materials are favored due to their durability and resistance to corrosion, along with their ability to safely transport gas under pressure.

Iron and steel are commonly used because they provide strength and are suitable for high-pressure applications. Copper is also effective, particularly in residential installations, due to its resistance to corrosion and ease of installation. Brass, an alloy of copper and zinc, is often used for fittings because it offers excellent corrosion resistance and mechanical strength. Aluminum is lightweight and resistant to corrosion, making it useful in certain types of installations, while plastic (specifically, types that are rated for gas use like PE or PVC) is utilized for its flexibility and ease of installation.

This combination of materials ensures that gas systems can be safely and effectively installed and maintained, reducing the risk of leaks and other hazards associated with gas transport. Other options presented either consist of materials that are unsuitable for the structural and safety requirements of gas systems or are not recognized as meeting industry standards for gas piping.