Which fittings are appropriate for use when supplying fuel gas?

The correct selection indicates that plastic, steel, or brass fittings are all appropriate for use when supplying fuel gas. This is based on the properties and safety standards associated with each type of fitting.

Brass fittings are commonly used due to their strength, resistance to corrosion, and ability to maintain a secure connection under pressure, which is critical in gas supply applications. They are also compatible with a variety of gases and have excellent durability.

Plastic fittings, specifically those made from high-density polyethylene or similar materials, are suitable for certain applications, particularly in underground installations where corrosion can be a significant concern. They are lighter and easier to handle, making them practical in specific scenarios.

Steel fittings are widely used in gas distribution systems due to their robustness and ability to withstand high pressure. Galvanized steel, in particular, is favored for its added layer of protection against corrosion.

Overall, the inclusion of all three types of fittings reflects adherence to the National Fuel Gas Code, which emphasizes the importance of using appropriate materials based on safety, installation requirements, and the specific characteristics of the gas being used.