Which fire suppression system is designed to fill up with water only when triggered?

The preaction system is the correct fire suppression system designed to fill up with water only when triggered. This system is a combination of dry and wet systems. In a preaction system, the pipes are filled with air rather than water under normal conditions. Only when a fire is detected and the system is triggered does the valve open, allowing water to flow into the pipes and activate the sprinklers. This design helps to reduce the risk of accidental discharge, making it particularly suitable for places where sensitive equipment or materials are stored.

In contrast, the wet-pipe sprinkler system is always filled with water and is ready to activate immediately upon detection of heat or smoke. The dry-pipe sprinkler system, on the other hand, is filled with air and does not have water until a trigger activates the valve, which may lead to delays in extinguishing fires. The deluge system, often used in high-hazard areas, operates by releasing a large volume of water simultaneously through open sprinklers when activated, which means the pipes are not pre-filled with water like in a preaction system.