What does a single yellow light on the HUD indicate?

A single yellow light on the Heads-Up Display (HUD) signifies that the SCBA’s air supply is at the 1/2 bottle level. This alert is crucial for ensuring that a user is aware of their remaining air supply while operating in environments that may demand full attention, such as hazardous situations. When this indicator lights up, it serves as a reminder for the user to monitor air usage and plan for a refill before the supply gets critically low. Understanding these signals is essential for safety and effectiveness during operations involving self-contained breathing apparatus.