In systems with emergency reserve, which alarm will activate when the changeover to the reserve supply occurs?

• A. Area
• B. Local
• C. Master
• D. Local and Master

Answer: (C)

When a hospital’s emergency reserve kicks in, the changeover is a system-wide action coordinated at the central gas control. The Master alarm is the warning that signals staff that the primary supply has been interrupted and the system is now using the reserve. Local alarms alert only a single device or regulator, and area alarms warn a specific zone, but neither is the primary indicator of the overall changeover. Because the event affects the entire gas system, the master annunciator is activated to prompt a facility-wide response.