When handling live electrical equipment, which of the following is critical?

Using non-conductive tools is critical when handling live electrical equipment because these tools help prevent accidental electrical shock and create a safer working environment. Non-conductive materials, such as rubber or plastic, do not allow electricity to flow through them, which is essential when working with or near energized circuits. This precaution reduces the risk of electrical hazards, making it a fundamental practice for anyone working in environments where live electrical equipment is present.

While other options like wearing standard safety glasses or having a backup power supply may enhance safety in specific contexts, they do not directly address the immediate risks associated with electricity conductivity. Similarly, completing training courses is vital for understanding electrical safety and code compliance but does not provide the practical protection that non-conductive tools offer during active work with live equipment. Thus, using non-conductive tools is the most critical factor in ensuring safety when dealing with live electrical systems.