What section of the central supply system supplies the system when the primary supply has been depleted?

The correct choice is based on the role of the secondary supply in a central supply system for medical gases. The secondary supply acts as a backup or supplemental source of gas that becomes operational when the primary supply is depleted. This is crucial in medical facilities, where a continuous and reliable supply of gases such as oxygen and nitrous oxide is necessary for patient care and safety.

The secondary supply is designed to automatically or manually engage once it detects that the primary gas source has reached a low level or has been exhausted. This ensures that there is no interruption in the availability of medical gases, which is vital for various medical procedures and patient needs.

In the context of medical gas systems, the operating supply refers to the gas currently being utilized, while the primary supply is the main source of gas. The reserve supply, on the other hand, generally refers to additional gas supplies that are available for emergency situations or extended use but do not immediately serve as a replacement for the primary supply. Understanding the specific functions of these components is essential for maintaining safety and compliance with NFPA 99 standards.