To facilitate service, testing or replacement, all pressure switches and mainline gauges downstream of the source valve shall be provided with a ________________.

To facilitate service, testing or replacement, all pressure switches and mainline gauges downstream of the source valve shall be provided with a ________________.

• A. Shutoff valve
• B. Demand check fitting
• C. D.I.S.S. fitting
• D. Check valve

Answer: (B)

When maintaining a medical gas line, you want to protect the supply and prevent gas from leaking or backflowing during service. Downstream of the source valve, pressure switches and mainline gauges should have a demand check fitting. This device acts as a one-way valve that opens to allow testing or monitoring when there is an actual gas demand, but closes to prevent gas from flowing back toward the source or escaping if the downstream equipment is disconnected or the valve is opened for service. This keeps the rest of the system pressurized and minimizes gas loss during maintenance. In contrast, a simple shutoff valve only provides isolation, a generic check valve might prevent backflow but isn’t specifically a service-friendly connection, and a DISS fitting governs interface compatibility but doesn’t offer the protective, one-way function needed for safe servicing.

When maintaining a medical gas line, you want to protect the supply and prevent gas from leaking or backflowing during service. Downstream of the source valve, pressure switches and mainline gauges should have a demand check fitting. This device acts as a one-way valve that opens to allow testing or monitoring when there is an actual gas demand, but closes to prevent gas from flowing back toward the source or escaping if the downstream equipment is disconnected or the valve is opened for service. This keeps the rest of the system pressurized and minimizes gas loss during maintenance.

In contrast, a simple shutoff valve only provides isolation, a generic check valve might prevent backflow but isn’t specifically a service-friendly connection, and a DISS fitting governs interface compatibility but doesn’t offer the protective, one-way function needed for safe servicing.