What does a rapid flashing red light indicate on the face piece's HUD?

A rapid flashing red light on the face piece's Heads-Up Display (HUD) is an important visual alert that indicates the firefighter has approximately 25% of their air supply remaining. This warning is critical for ensuring operational safety, as it signals the need for the firefighter to consider exiting the hazardous environment or finding a source of breathable air soon. Understanding these indicators is vital for maintaining situational awareness during firefighting operations and for effective self-preservation strategies in life-threatening situations.

In contrast, the other options reflect higher air supply levels, which do not trigger the rapid flashing red light, as those markers are associated with safer air supply levels that do not yet require immediate action.