Pre-action fire suppression systems are similar to Wet Sprinkler Systems. The defining difference with pre-action systems is that water is not stored in the overhead piping. There are two main types of pre-action systems: single interlock and double interlock.
A single interlock system requires that a preceding fire detection event, usually the activation of a heat or smoke detector, takes place prior to the action of water being introduced into the systems piping. This is accomplished by the opening of the pre-action valve which is usually located at the fire riser.
The operation of a double interlock system requires that both a preceding fire detection event, usually the activation of a heat or smoke detector and an automatic sprinkler operation takes place prior to the action of water being introduced into the systems piping. This is accomplished by the opening of the pre-action valve and through the loss of air pressure at the automatic sprinkler.
Activation of either the fire detectors alone or sprinklers alone, without the concurrent operation of the other, will not allow water to enter the piping. Because water does not enter the piping until a sprinkler operates, double interlock systems are considered to be dry systems.
Prior to fire detection, if the sprinkler operates, or the piping system develops a leak, loss of air pressure in the piping will activate a trouble alarm. In this case, the pre-action valve will not open due to loss of supervisory pressure, and water will not enter the piping.
Pre-action sprinkler systems are specialized for use in locations where accidental activation is undesired, such as in Data Centers. They provide protection of computer equipment from accidental water discharge. However, if a pre-action suppression system is discharged, critical equipment will still experience extensive water damage.
For these reasons, DP Air recommends a Gas (Clean Agent) System is used in conjunction with a pre-action suppression system for all critical environments. In most cases, a commercial facility is required to have a fire sprinkler system in all areas by code, even if you have an agent system in place. If there were no code requirement for a sprinkler system, it is still recommended to have the pre-action system as a backup system in the event that the agent system does not extinguish the fire completely or if another fire flares up after the agent system has discharged and dispersed. The agent fire suppression system is a one-shot system. The pre-action sprinkler system would continue to douse a fire until it is extinguished.
To learn more about fire suppression options, please contact DP Air today to speak with a specialist and schedule a consultation.