- 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