What safety measure should be taken when disconnecting an air start unit?

When disconnecting an air start unit, the paramount safety measure is to wait for the captain's clearance. This step is critical because the captain has the overall responsibility for aircraft safety and operation. Ensuring that the engine is off, securing equipment, and notifying the maintenance crew are also important considerations, but they do not take precedence over obtaining the captain's explicit permission to proceed with the disconnection. The captain's clearance indicates that it is safe to disconnect the air start unit, preventing any potential mishaps or accidents that could arise if the disconnection were to occur while the engine or other critical systems are still operational. This protocol emphasizes the importance of communication and adherence to operational procedures to ensure the safety of all personnel involved.