In a two-stage fire alarm system, what characterizes the preliminary alarm compared with the full alarm?

• A. A preliminary alarm disables life safety devices.
• B. A preliminary alarm only sounds audible notification without visual alerts.
• C. A preliminary alarm may alert building personnel or secure areas, while a full alarm notifies occupants and activates NACs.
• D. A preliminary alarm triggers full evacuation immediately.

Answer: (C)

In a two-stage fire alarm system, the first stage is a preliminary alert meant to warn building personnel and secure areas, giving responders a chance to assess the situation before evacuating everyone. The second stage is the full alarm, which notifies occupants throughout the building and activates the main notification circuits (NACs) to ensure everyone is alerted and can evacuate. This staged approach helps avoid unnecessary evacuations while enabling a proper, coordinated response if the situation requires it. So, it’s correct to say the preliminary alert may alert staff or secure areas, while the full alarm notifies occupants and activates NACs.