Which wiring method is permitted for use in a duct that transports dust?

In the context of wiring methods for ducts that transport dust, it is crucial to prioritize safety and compliance with codes that protect against potential fire hazards and equipment failure due to dust accumulation. Ducts that carry dust can create a situation where the buildup of dust might interact negatively with electrical components, leading to risks such as short circuits or fires.

Metallic conduit is often considered for its durability and ability to provide a shield against electromagnetic interference; however, in settings where dust is present, it can become problematic. Dust can accumulate inside the conduit, and since metallic conduits can potentially create dust clouds or hazards if damaged, they are not ideal for such applications.

On the other hand, non-metallic conduits, while resistant to corrosion and lighter, may also not be suitable because their surfaces can attract dust, which may then lead to buildup inside the duct.

For these reasons, the standards likely dictate that neither wiring method is appropriate for use in ducts transporting dust. This concern for potential hazard and maintenance issues leads to the conclusion that appropriate wiring methods should be avoided altogether in such environments, supporting the idea that none of the options provided are permitted for this specific application.