Unused openings in cabinets and panelboards must be effectively what to ensure protection?

Unused openings in cabinets and panelboards must be effectively closed to ensure protection against various environmental factors and to maintain the safety of the electrical system. When openings are left unprotected, there is a risk of dust, moisture, and foreign objects entering the enclosure, which could potentially cause short circuits or other electrical failures. Closing these openings helps maintain the integrity of the electrical system by preventing contaminants from compromising components or leading to unsafe conditions.

In addition, effectively closing these openings can also reduce the likelihood of accidental contact with live parts, enhancing overall safety for both personnel and equipment. Proper closure aligns with electrical code requirements, which emphasize the importance of protecting electrical installations from external elements that could impair their function and safety.