Under what condition are employees allowed to work in shields during installation?

The correct answer emphasizes the importance of ensuring a safe work environment when installing shields. Employees are permitted to work in shields during the installation process specifically when the area is clear of other workers. This condition is crucial because it minimizes the risk of injury from falling objects or accidents that could occur during the installation.

By ensuring that the area is free of other personnel, it allows those working on the installation to focus entirely on their tasks without distractions or the potential hazards posed by others nearby. This safety measure aligns with industry standards and regulations aimed at protecting workers during construction and excavation activities.

The other conditions do not sufficiently address the critical aspect of worker safety during the installation of shields. For instance, using automated machines or moving shields vertically may introduce risks if other workers are present. Similarly, waiting for shields to be fully installed may delay necessary safety precautions that should be enacted the moment installation begins. Prioritizing a clear space for installation is a fundamental strategy for maintaining a safe work environment.