What is the necessary safety step before entering an escalator truss?

The correct choice is to install a mechanical lock before entering an escalator truss because this step is crucial for ensuring the safety of personnel working in or around potentially hazardous equipment. A mechanical lock serves as a physical barrier that prevents the escalator from being activated while maintenance or inspection is taking place, thereby protecting those inside the truss from unexpected movement or operation of the escalator.

In environments where machinery is used, it is essential to follow lockout/tagout procedures to control hazardous energies. By securing the escalator in a non-operational state, workers can perform their tasks without the risk of injury from the machine inadvertently starting.

While wearing safety goggles, checking the power source, and notifying a supervisor are important safety measures in the workplace, they do not specifically address the immediate risks associated with entering an escalator truss. Safety goggles are designed to protect the eyes from debris; checking the power source is a general safety check but does not provide the specific protection needed in this scenario; notifying a supervisor is a good practice but does not directly prevent hazards associated with machine operation. Thus, installing a mechanical lock stands out as the most critical step in preventing accidents in this context.