The PRE-ACTION SYSTEM is especially manufactured for the applications where to avoid any accidental activation of the system is decisive or as replacement of extended dry sprinkler systems to make their operating faster. These systems are excellent for data processing centres, control centres, bookshops, valuable documents archives and refrigerating rooms. In some cases, the pre-action systems, combined with carbon dioxide extinguishing systems underfloor, may replace the classic gas extinguishing systems.Those systems using a single interblock device need a detection device before the water reaches the distribution tubes and the sprinklers. This system prevents from flooding caused by accidental breaks. Water can flow in the protected area only when the detection device alarm is activated. While, in the double interblock device systems, before the water reaches the distribution system, both the detector device and the sprinkler crash are necessary. This scheme guarantees an even higher protection against any damage caused by accidental discharges.