Which warning light indicates it is time to vacate the scene in a PBE unit?

The correct response is based on the understanding of various warning signals used in Personal Breathing Equipment (PBE) units. The light that signals it's time to vacate the scene is characterized by an alternating green and red light. This indicates a hazardous situation where immediate action is necessary to ensure safety.

The combination of green and red serves as a clear visual alert to crew members that conditions have deteriorated or become unsafe, prompting them to evacuate or take alternative actions. This specific color combination is designed to be highly noticeable and distinct from other warning signals, ensuring that it effectively captures the attention of individuals in the vicinity.

Other warning lights, such as a steady red light, typically may signify an alert but do not inherently indicate the need to evacuate. A steady green light generally serves a different purpose, often indicating operational readiness or safety, while a blinking yellow light is usually associated with caution and may not necessitate immediate departure from the area. Understanding the function of these lights and their implications is crucial for ensuring safety in emergency situations.