Final answer:
Preaction system alarms are triggered when the valve is opened, which occurs after the fire detection system is activated. Preaction fire sprinkler systems utilize both detection and a heat trigger to minimize accidental discharges, ideal for protecting sensitive environments.
Step-by-step explanation:
Preaction system alarms are given as soon as the valve is opened. A preaction fire sprinkler system is a type of fire suppression system commonly used in environments sensitive to water damage.
It employs a two-step process for water release: the activation of a fire detection system which prepares the system, followed by the opening of the preaction valve due to a rise in temperature or a secondary activation method.
In a preaction system, the piping is normally filled with air, and water is held back by the preaction valve. Once a fire is detected by the fire detection system, the preaction valve is opened, allowing water to fill the piping. This way, accidental water discharge is minimized, as both a fire detection event and a heat trigger at the sprinkler heads are needed for water release.
Because preaction systems require two triggers before water is released, they are widely used in settings such as data centers, libraries, and archives where accidental water discharge must be strictly avoided to protect sensitive materials or equipment.