Which section of the central supply system supplies the system when both primary and secondary supplies are exhausted?

The correct choice is related to the concept of redundancy and safety in medical gas supply systems. The reserve supply section of a central supply system is specifically designed to provide an additional source of gas when both the primary and secondary supplies have been exhausted. This ensures that there is always a backup available, which is critical in medical environments where the availability of gases such as oxygen and nitrous oxide can be life-saving.

In healthcare facilities, the reliance on continuous access to medical gases necessitates multiple layers of supply. The primary and secondary supplies are intended to handle regular consumption and can often be depleted due to high demand or an unforeseen circumstance. The reserve supply acts as a safeguard against complete supply failure, helping to maintain continuous operation and patient safety.

Thus, the reserve supply is essential for ensuring that there is a fallback option, demonstrating the importance of comprehensive planning in the design of medical gas systems.