What action must be taken by the fire guard after APU fuel/oil system maintenance?

After maintenance on the APU fuel/oil system, it is crucial for the fire guard to examine the APU for any leaks and communicate any issues identified. This is an important safety measure because the fuel and oil systems are critical to the operation of the APU, and leaks could present significant hazards, including fire risks and environmental concerns. The fire guard's role includes ensuring that the area is safe for operations by closely monitoring these potential issues.

Monitoring the APU without checks would not fulfill the necessary safety protocols after maintenance, as it could allow undetected leaks to pose serious risks. Starting the APU immediately without checking for leaks could exacerbate any existing issues and create hazardous conditions. Disconnecting the APU fuel line would be an impractical action post-maintenance, as it would defeat the purpose of preparing the APU for operational readiness. Therefore, examining for leaks and communicating any found issues is the most responsible and safety-oriented action to take in this scenario.