After hearing the warning bell sound on an SCBA tank, how much air is left in cubic feet?

The warning bell sound on a Self-Contained Breathing Apparatus (SCBA) indicates that the air supply is critically low, alerting the user to exit the hazardous area immediately. When the warning bell activates, it is commonly understood that there is approximately 35 cubic feet of air remaining in the SCBA tank. This threshold serves as a crucial safety measure, allowing firefighters to maintain awareness of their air supply and ensuring they have enough time to safely evacuate.

In contrast, the other options represent amounts of air that exceed what is generally available when the bell rings, leading to potentially dangerous situations if one were to rely on higher amounts of available air when the alarm sounds. Understanding this specific detail helps firefighters manage their resources effectively during an operation.