What does one green light on the HUD signify?

One green light on the Heads-Up Display (HUD) of a Self-Contained Breathing Apparatus (SCBA) indicates that the air supply in the tank is at the 3/4 full mark. This visual signal provides users with a quick and clear status of their air supply, allowing them to manage their breathing supply and make informed decisions about their safety while in hazardous environments.

Having this information readily available is crucial, as it helps the wearer to monitor their usage and determine when they may need to exit a dangerous area or switch to another tank. Understanding how the HUD operates and what the lights signify is vital for maintaining situational awareness and ensuring effective use of the SCBA in emergencies.