55. If you observe any situation which presents a safety or pollution hazard during fuel transfer operations, what action should you take FIRST?

Immediately stopping the fuel transfer operation is the priority action to mitigate safety or pollution hazards, as it directly eliminates the source of the risk before any follow-up measures are taken. Regulations and established procedures mandate the ability to immediately halt fuel transfer in unsafe conditions, preventing further fuel movement and minimizing potential incidents like spills or fires. Subsequent actions, such as valve closures, notifications, or alarms, are secondary to this initial step of shutting down the transfer.