• All sprinkler heads are pre-opened
• A signal from a detection device mechanically opens a water valve
  • water fills the pipes and flows from all heads
  • water flows until shut off,
  • system is reset
• Primarily installed in special hazard areas that have fast spreading fire
• Usually requires several detectors to activate before discharging.

Pipes in protected area are empty; a detector signal triggers the system, allowing water/foam to enter pipes and flow from all sprinkler heads (which are already open