Which valves must be operable from a standing position outside of the room, on the same floor as the points of use they serve?

The correct choice is zone valves, which are crucial components in medical gas systems. Zone valves are designed to control the flow of medical gases to various areas within a facility, such as patient rooms or operating theaters. The requirement for these valves to be operable from a standing position outside of the room ensures that medical personnel can easily and quickly access and manipulate the gas supply without needing to enter potentially hazardous environments or interrupting patient care.

By placing zone valves in this accessible location, it enhances the safety and efficiency of the gas management system. If an emergency arises, such as a need to quickly shut off gas supply to a room, personnel can respond swiftly without delays. This design consideration is vital for maintaining the proper functioning of medical gas systems and ensuring patient safety.

Relief valves, backflow preventers, and isolation valves have different functions and are typically installed for different operational requirements. Relief valves are primarily concerned with pressure regulation and preventing overpressure conditions, while backflow preventers are installed to protect the integrity of the gas supply by preventing contamination. Isolation valves serve a specific purpose of segmenting sections of the gas system for maintenance or emergency situations but may not necessarily need to be operable from outside the room in the same way that zone valves do.