When nonmetallic wiring methods are exposed to chemical agents, they must be resistant based on what?

The requirement for nonmetallic wiring methods to be resistant to chemical agents is grounded in their being listed for the specific reagent. This means that the materials used in these wiring methods must be tested and certified to demonstrate their durability and resistance to the specific chemicals they may encounter in their environment.

When materials are "listed," it indicates that they have undergone evaluation by a recognized testing laboratory to ensure that they meet specific performance standards essential for safety and longevity. This is especially critical for nonmetallic materials, which could be more susceptible to degradation when exposed to certain chemicals, impacting their integrity and function.

Factors like chemical composition, material classification, and government regulations do play a role in selecting wiring methods, but the direct assurance of performance under specific conditions is provided by the listing for the reagent, emphasizing the importance of testing and certification in ensuring the safety and reliability of electrical installations in potentially hazardous environments.