Deluge Water spray systems are similar to automatic sprinkler system except all nozzles are open and will discharge together when control valve opens. These systems are designed to protect areas where fire is likely to spread rapidly and / or where cooling of surrounding equipment is necessary.

In some circumstances extinguishment is not always desirable, only cooling. Common applications include power generation equipment (e.g. switchgear), flammable liquid storage, gas tanks and process plants.
Cooling is achieved by the use of medium velocity spay nozzles and extinguishment by usually by high velocity nozzles. This system can be activated manually or automatically by hydraulic, pneumatic or electrical detection systems. This type of system also needs sufficient water flow and pressure to contain or extinguish the type of hazards they are there to protect.