It is not infrequent to intervene on existing firefighting systems for maintenance, in order to ensure the proper functioning and the efficiency in case of activation. Consequently, the proper “maintenance of fire protection systems” plays a fundamental role in maintaining the guarantee of these requirements in its lifetime. The maintenance, being it ordinary or extraordinary, may bring to partial modification of the system, as long as it does not lead to a variation or “Substantial Change”. In the D.M. 12.20.2012 (commonly known as “Decreto Impianti”) the Substantial Change is defined as “a transformation of the original system type or extension of its typical size for more than 50% of the original, if not defined by a specific regulation or rule “. So, in case of a NON substantial modification of an old but efficient and functional sprinkler system, it will not be necessary to be verified according to the new legal regulations, but complete compliance with the rule by which it had been designed and built will be enough. In fact, the possibilities are many and all of them valid. It is therefore in the ability and skill of the designer to understand and decide what is the best way to proceed with: simply re-checking the system according to the old regulator, considering the modified system as a new one and then testing it according to D.M. 20/12/2012, or even designing a new sprinkler system. Meeting regulatory parameters does not always mean well-designing systems. In some cases, in fact, it is necessary to make critical choices for a greater safety and efficiency of the system.
We propose one of our recent experience about the modification of a Natural Evacuation System in a shopping center in northern Italy, which is a union of two buildings built in different moments, where the new part of the structure has got natural smoke and heat evacuators. The customer has NOT been proposed to change the system by adding further natural vents and to verify it once again according to the reference standard, as this operation was proving difficult to achieve, if not excessively high costing. The optimal solution proposed, and accepted by the customer, was to install a forced evacuation system in the old part of the building in addition to the natural evacuation system. However, the whole system was designed and tested according to the French standard “EN 246” (INSTRUCTION TECHNIQUE EN 246), which allows the coexistence of the two systems (natural extraction, and forced removal), in compliance with the DM 20-12 / 2012.