In completed installations, each outlet box must have:

In completed installations, it is essential for each outlet box to have a cover. This requirement serves several important functions in electrical systems. First, the cover protects the internal wiring and components from dust, dirt, moisture, and accidental contact, which can lead to electrical faults or hazards. By keeping the contents of the outlet box enclosed, it also prevents issues such as short circuits and electrical shocks that could occur if someone were to inadvertently touch live conductors.

Additionally, the cover helps maintain the overall aesthetic of the installation, providing a neat and finished appearance. It also complies with electrical codes and standards that mandate the use of covers to ensure safety and reliability in electrical systems. Failure to use a cover could lead to code violations and potential safety hazards in residential or commercial environments.

While accessibility for maintenance, ventilation openings, and proper labeling are all important considerations in electrical installations, the primary and most immediate requirement specifically addressed by the question pertains to the necessity of a cover for each outlet box.