Types of fire sprinkler systems
There are four main types of fire sprinkler systems. The type of fire sprinkler system you have is determined by a few factors like hazard type and size and building type and size. It depends on the type of sprinkler system you have when addressing the question of sprinkler head activation.
The main system types are:
- Wet pipe systems that contain water in the piping network.
- Dry pipe systems that contain pressurized air/nitrogen in the piping network and hold water back with a valve.
- Pre-action systems that are dry systems but hold water back with an electronically activated valve.
- Deluge systems that are a type of dry system where water is held back by a valve with sprinkler heads always open.
All of these sprinkler types, with the exception of a deluge system, are closed head systems. This means that each sprinkler head is held closed by either a heat-sensitive glass bulb or a two-part metal link held together with fusible alloy. The glass bulb/link applies pressure to a pipe cap which prevents eater from flowing though the piping system. When the ambient temperature around a sprinkler head or nozzle reaches the activation temperature, water flows out of that sprinkler head.
This is the reason that, for most sprinkler systems, in the event of a fire emergency only one sprinkler will off, not all. Each sprinkler activates independently when the predetermined heat level is reached (typically 135-165 degrees Fahrenheit) so only sprinklers near the fire will operate. In the event of a larger fire, several sprinklers may operate but only those in the vicinity of the fire.