A portable air supply for use in rescuing a firefighter that has run out of air is called a/an:

The correct choice is a rapid intervention pack, which is specifically designed for emergency situations, especially for rescuing firefighters who may be in distress or have run out of air while in the field. Rapid intervention packs are typically equipped with a portable air supply that allows for quick deployment and provides a firefighter with the immediate breathing support they need to ensure their safety during a rescue operation.

These packs are an essential component of firefighter safety and are meant to facilitate rapid response to emergencies where time is critical. They usually contain a high-pressure cylinder with a regulator that can supply air quickly to the downed firefighter.

In contrast, a portable oxygen tank is not typically used for fire service rescue operations. It is designed for medical applications where supplemental oxygen is required but does not provide the same functionality or protection as a rapid intervention pack in a firefighting context.

A portable SCBA (self-contained breathing apparatus) is an individual breathing apparatus used by firefighters during operations. While it serves the purpose of providing breathable air, it is not primarily aimed toward rescuing another firefighter in distress.

A rescue air pack could imply a similar function to a rapid intervention pack, but the terminology can vary, and not all fire departments use this specific term. It's essential for clarity and operational effectiveness that the