What piece of emergency equipment must be located within three feet of each required fire extinguisher in the passenger cabin?

The piece of emergency equipment that must be located within three feet of each required fire extinguisher in the passenger cabin is the Protective Breathing Equipment (PBE). This requirement is rooted in safety protocols that aim to ensure the immediate availability of essential firefighting tools and protective gear during an emergency situation.

The PBE is designed to provide oxygen in the event of smoke or fire, allowing crew members to effectively manage a fire situation while maintaining their ability to breathe without inhaling hazardous fumes. Its proximity to the fire extinguisher is crucial because, in a fire scenario, crew must quickly access both the extinguisher to combat the fire and the PBE to protect themselves from respiratory hazards.

The other options, although important in the context of overall safety, do not have the same specific requirement for proximity to fire extinguishers. For instance, first aid kits are essential for addressing medical emergencies, but they are not necessarily required to be within three feet of a fire extinguisher. Similarly, emergency flashlights and life vests serve important functions but do not directly support firefighting efforts in the same way that PBE does. Therefore, the primary focus of ensuring the safety of crew members while combating a fire makes the PBE the correct answer