Which type of materials is required to be listed for conduits, raceways, factory elbows, and associated fittings?

The correct answer is that all types of materials must be listed for conduits, raceways, factory elbows, and associated fittings. This requirement ensures that any materials used in electrical installations comply with relevant safety standards and regulations.

Materials such as PVC, metal, or any other material used for these components must be tested and certified to ensure their performance and safety characteristics. This listing confirms that they have undergone rigorous testing by a recognized standard organization, thereby reducing the risk of failure during operation and ensuring the safety of electrical systems.

Only using certain types of materials, such as PVC or metal, would not meet the comprehensive standards set forth for safety and reliability in electrical infrastructure. Hence, it is vital that all materials intended for use in this context are appropriately listed to ensure they are suitable for the application and comply with any pertinent codes or regulations.