What must occur before water is released in preaction sprinkler systems?

In preaction sprinkler systems, a secondary device must be activated before water is released. These systems are designed with an added layer of safety for environments where accidental activation could lead to significant damage, such as in computer rooms or museums.

The preaction system is typically composed of two stages: the first stage involves the detection of heat or smoke by a fire detection device, activating an alarm and opening a valve that fills the system with water. However, the water is not released into the pipes until a second condition is met, often involving either heat from a fire reaching a specific temperature threshold or smoke detection confirming a fire’s presence.

This two-step process ensures that water is only released when a fire is confirmed, thus minimizing the risk of accidental discharge while still providing an effective means of fire suppression. Other options like manual activation or pressure drops do not inherently trigger the release of water, as preaction systems are primarily reliant on confirming the presence of a fire through an additional detection device.