During a fire emergency, what must be secured to a passenger experiencing shortness of breath?

In the event of a fire emergency, a passenger experiencing shortness of breath must be secured with the oxygen mask. This is essential because a fire can consume oxygen and produce smoke and toxic gases, making it difficult for passengers to breathe. Providing an oxygen mask ensures that the individual has access to a supply of fresh air, which is critical for maintaining their oxygen levels and preventing further respiratory distress.

Using an oxygen mask can also stabilize the passenger's condition, allowing them to remain calm and alert while awaiting further assistance. It is a direct response to the immediate needs of someone who is struggling to breathe due to compromised air quality from the fire. Other options do not address the immediate health and safety needs of the passenger directly affected by the fire conditions.