The risk of storage plant of pyrotechnics Basco A. 1 , Cammarota F. 1 , Salzano E. 1 , Istituto di Ricerche sulla Combustione - C.N.R., Via Diocleziano 328, 80124 Napoli (I) Recent updating of Seveso Directive have made mandatory safety report of storage plants of pyrotechnics (fireworks). However, few guidelines are published in the open literature. The following work deals with the determination of maximum explosion pressures in confined and vented enclosures containing hazardous substances ranging from high-energy explosives to low-energy pyrotechnics. 1. Introduction Recent accidents involving fireworks, as that occurred in Enschede (NL), have induced important variation in the Seveso Directive (Directive 96/82/EC) and Directive 2007/23/EC, which now include firework storage plants other than manufacturing installations. The most common pyrotechnics used in Europe are called display pyrotechnics, i.e. solid mixtures which react with relative slow rates of reaction with the terminal effect of light, heat, smoke or sound resulting from an exothermic oxidation- reduced chemical reaction. Despite the low reactivity, recent experimental tests (CHAF, 2002) have demonstrated that large amount of fireworks stored in closed environment may explode with en mass behaviour. On the other hand, scientific and technical publications are largely available for high-energy explosives whereas very few data are available for lower energetic pyrotechnics. Also important worldwide references about the use of flammable and explosive materials such as NFPA1124, NFPA1123, NFPA1126 give several information on safety distances and recommendation for the manipulation of explosives and fireworks whereas storage design and risk assessment guidelines are neglected. Neither public military guidelines (TM 5-1300, TM 9-1300-214) are really useful for the producers and design engineers when safety of low-energy pyrotechnics are considered. In the following, the explosion phenomenon of high-energy explosives and pyrotechnics in closed and vented storage containers is analysed. Plots of pressure with respect to volume ratio V/V° (the room space over the pyrotechnic volume) are shown. These plots can be usefully adopted for engineering practice of storage design of pyrotechnics. Finally, a large set of TNT explosions in vented enclosures have been analysed in order to produce simplified design guidelines and correlations for the maximum pressure within the explosion room or outside the vent section. Furthermore, insights on excess air requirement and vent effectiveness are also given.