Which type of sprinkler system uses a secondary device to activate water flow?

A preaction sprinkler system is designed to prevent accidental water discharge and is particularly beneficial in environments where water damage from activation could be catastrophic, such as data centers or archives. This system employs a secondary device, typically a heat or smoke detector, that detects a fire condition before allowing water into the pipes. The flow of water is only activated after the secondary device has been triggered, meaning that the pipe remains dry until the detection of a fire, thus minimizing the risk of unwanted water damage.

In contrast, wet systems have water constantly maintained in the pipes, which reduces response time but risks accidental activation. Dry systems contain pressurized air instead of water, allowing for use in colder environments where freezing might be a concern, and they activate water flow when a sprinkler head opens, without a separate activation device. Deluge systems have open sprinkler heads and utilize a detection system to release large volumes of water immediately upon detection of a fire but do not use a secondary device to control water flow individually for each sprinkler. Each of these systems has its unique operational strategies and applications, but the preaction system's dual-layer activation mechanism set it apart.