Mock Exam Diagram 1 Indicates Valves #5, 6 & 13 are _______.

• A. zone valves
• B. isolation valves
• C. service valves
• D. riser valves

Answer: (A)

Zone valves are the devices used to shut off or isolate an entire defined area of the medical gas distribution system. When you see valves positioned at the boundary of a zone in a diagram, they’re intended to control the gas supply to all outlets within that zone. This allows maintenance or emergency isolation of just that area without affecting other zones in the building.

Isolation valves, by contrast, are meant to shut off gas to a single line, piece of equipment, or a smaller segment—not an entire zone. Service valves are used for testing or calibration and are typically located at ports or near regulators for commissioning and maintenance. Riser valves sit on vertical risers and are used to isolate supply that runs up through the building, not to isolate a specific zone.

So the valves in the diagram function as zone valves because their role is to control the gas supply to a whole zone rather than to a single outlet or a vertical riser.