What valve must be operable from a standing position in the corridor it serves?

The correct answer is the zone valve. Zone valves are installed within a medical gas piping system to control the flow of medical gases to specific areas, or "zones," of a facility. It’s necessary for these valves to be operable from a standing position in the corridor to facilitate easy access and operation during emergencies or routine maintenance. Since medical gas flow may need to be adjusted quickly, having these valves accessible and operable this way ensures that staff can respond efficiently without the need to enter potentially hazardous areas.

Isolation valves and main valves serve different purposes, typically related to shutting off the gas supply to larger sections of the system or the entire system, and may not have the same accessibility requirements. Emergency valves are designed for immediate use in critical situations but may not specifically require the same operational accessibility from a standing position in corridors. Understanding the specific functions and positioning of each valve type is essential for the safe management of medical gas systems.