In the event of a significant laboratory fire, what should be the first steps taken?

The first steps taken in the event of a significant laboratory fire are crucial for ensuring the safety of all personnel and minimizing damage. The correct sequence of actions should prioritize the immediate safety of individuals in the lab, activation of emergency protocols, and containment of the fire.

Starting with rescuing personnel is vital, as it ensures that anyone in immediate danger is helped first before taking other actions. Following this, hitting the alarm alerts others in the building about the fire, prompting them to take appropriate actions for their safety. Closing the lab door helps contain the fire and smoke, preventing it from spreading further and providing a buffer for those evacuating. Evacuating should be the last step in this sequence, allowing sufficient time to assist others and to ensure collective safety as everyone exits the premises in an orderly manner.

This orderly approach highlights the importance of prioritizing human life as the first consideration, followed by alerting others and containing the situation, which is why the sequence in option D is the most appropriate in the context of emergency response protocols in a laboratory setting.