Valve #7 is the _________ where the main line enters the building.

• A. emergency shut-off valve
• B. main line valve
• C. service valve
• D. source valve

Answer: (B)

In a medical gas distribution system, the main line valve is the valve located at the point where the building's main gas line enters, and its function is to isolate the entire pipeline for maintenance or emergencies. That placement directly corresponds to Valve #7’s described location, making it the appropriate term. The other valves serve different purposes: an emergency shut-off valve is used for rapid shutdown in a specific area or at a critical point, not the entry to the building; a service valve isolates downstream service lines to individual equipment or areas; and a source valve is located at the gas source itself, controlling supply before the gas even enters the building.