Which of the following indicates a full SCBA cylinder according to HUD readings?

Having two green lights on the Heads-Up Display (HUD) is the correct indication of a full SCBA cylinder. This visual signal is designed to provide quick and clear status updates to users about the air supply. When the HUD displays two green lights, it signifies that the cylinder is at a full or near-full capacity, ensuring the user can safely operate in hazardous environments without the immediate concern of running out of air.

In contrast, yellow lights typically indicate a lower level of air pressure and may signal the need for the wearer to monitor their air supply closely or prepare for a refill. A red light, on the other hand, is a critical warning indicating that the air supply is low and urgent action is required to ensure safety. One yellow light, similar to the single red light, also reflects a less favorable condition, suggesting that the air supply is diminished and safety protocols may need to be enacted. Understanding this system of visual alerts is crucial for effective and safe operations in the field.