Globally more than ninety percent fire hazards are addressed by Sprinklers. Designing a sprinkler system one of the first decisions a designer has to make is what type of sprinkler system should be installed and there are wet, dry, preaction, and deluge types available for various applications.  Wet pipe sprinkler systems are the most common. In this system the sprinkler piping is constantly filled with water. When the temperature at the ceiling gets hot enough the glass bulb or fusible link in a sprinkler will break. Dry pipe systems are very similar to wet pipe systems with one major difference. The pipe is not constantly filled with water. Instead, the water is held behind a dry pipe valve usually some distance away from where the sprinklers are located. Like a wet pipe system, when the temperature at the ceiling becomes hot enough, the glass bulb or fusible link of the sprinkler breaks. Of all the sprinkler system types perhaps the most complicated is the preaction system. There are three different types of preaction systems, a non-interlock system, a single interlock system, and a double interlock system. Deluge systems are similar to preaction systems in that they use another type of detection for operation. However, the biggest difference is that deluge systems use open sprinklers or nozzles. Instead of getting water flow from individual heads that have operated, once water fills the system, water will flow from every sprinkler head. Much like a preaction system, a deluge valve will keep water from filling the system until the operation of another type of detection system, such as smoke detection. Once that detection system is activated, water not only fills the system but flows from the open sprinklers or nozzles.