What should be done with unused openings in boxes and fittings?

Unused openings in boxes and fittings should be effectively closed to prevent various issues that can arise from leaving them open. Closing these openings is important for a couple of reasons. First, it helps maintain the integrity of the electrical systems by preventing dust, debris, and moisture from entering, which can lead to corrosion or electrical failures. Second, sealing these openings contributes to safety by ensuring that no foreign objects can accidentally come into contact with live electrical parts.

The term "effectively closed" implies a thorough approach, ensuring that the closure method is appropriate for the type of box or fitting and the environment in which it's located. This is particularly critical in maintaining a safe and efficient electrical system, adhering to local codes, and ensuring compliance with best practices in trade competencies.