What indicator shows that the fire extinguisher has discharged due to thermal conditions?

The identification of a fire extinguisher discharge due to thermal conditions is effectively indicated by a thermal discharge indicator with a red disk. This specific type of indicator is designed to respond to changes in temperature, which typically occurs during a fire. When the thermal conditions reach a predetermined threshold, the red disk will activate, signaling that the extinguisher has discharged or that the system has been compromised in some way.

This mechanism is crucial in fire detection systems, particularly in environments where rapid temperature changes can pose significant risks. Having a visual and intuitive indicator like the red disk allows crew members and operators to immediately assess the situation and understand that the extinguisher has been activated, thereby facilitating a timely response to potential dangers.

The other options, while useful in their contexts, do not specifically serve as thermal indicators for extinguisher discharge. A colored light on the control panel might indicate various system statuses, but it may not directly relate to thermal discharge. An audible alarm in the cockpit might signal other types of alerts, and a visual gauge on the extinguisher itself typically measures pressure or readiness rather than specifically indicating discharge due to thermal conditions. Thus, the thermal discharge indicator with a red disk is uniquely suited for this purpose.