Which LED signal indicates a half-full air cylinder?

Which LED signal indicates a half-full air cylinder?

• A. Steady red
• B. Steady yellow
• C. One green, one red
• D. Yellow blinking

Answer: (D)

When monitoring air supply on an SCBA, LED indicators convey how much air remains. A blinking yellow signal is used to flag a mid-level condition—roughly halfway full. The blinking pattern grabs attention in smoky or dark environments and tells you you’re not at danger yet, but you should plan to swap cylinders soon. Green or steady green would typically mean the cylinder is full or okay. Steady red usually signals low or empty. A single red with a green somewhere else isn’t the standard half-full indicator. The combination of yellow color with a blinking pattern specifically communicates a caution level consistent with being about halfway depleted.

When monitoring air supply on an SCBA, LED indicators convey how much air remains. A blinking yellow signal is used to flag a mid-level condition—roughly halfway full. The blinking pattern grabs attention in smoky or dark environments and tells you you’re not at danger yet, but you should plan to swap cylinders soon.

Green or steady green would typically mean the cylinder is full or okay. Steady red usually signals low or empty. A single red with a green somewhere else isn’t the standard half-full indicator. The combination of yellow color with a blinking pattern specifically communicates a caution level consistent with being about halfway depleted.