What should a flight attendant do first in the event of a pressure seal leak?

In the event of a pressure seal leak, the first priority for a flight attendant is to notify the Pilot in Command. This step is critical because the pilot is responsible for the overall safety and management of the aircraft and is trained to handle various emergencies, including cabin depressurization. By promptly informing the pilot, the flight attendant ensures that the crew can initiate emergency protocols, such as descending to a safer altitude, activating oxygen systems, and preparing for possible evacuation if necessary.

The other options, while important in their own right, are typically part of the sequence that follows the initial notification to the pilot. Checking the cabin for passengers is crucial for assessing the situation and ensuring everyone's safety, but it is secondary to alerting the pilot. Evacuating the aircraft immediately may not be warranted in the case of a pressure seal leak, as the situation may be managed in-flight with the guidance of the pilot. Deploying oxygen masks is an essential response to cabin depressurization, but again, it is part of the coordinated actions that the pilot will direct after being informed of the leak. Hence, notifying the Pilot in Command is the first and most critical action for ensuring the safety of all onboard.