This European Standard describes the general requirements for explosion isolation systems. An explosion isolation system is a protective system, which prevents an explosion pressure wave and a flame or only a flame from propagating via connecting pipes or ducts into other parts of apparatus or plant areas. This European Standard specifies methods for evaluating the efficacy of the various explosion isolation systems, and methods for evaluating design tools for such explosion isolation systems when applying these in practice. This European Standard also sets out the criteria for alternative test methods and interpretation means to validate the efficacy of explosion isolations. It covers e.g.: a) general requirements for the explosion isolation components; b) evaluating the effectiveness of an explosion isolation system; c) evaluating design tools for explosion isolation systems. This European Standard is applicable only to the use of explosion isolation systems that are intended for avoiding explosion propagation between interconnected enclosures, in which an explosion may result as a consequence of ignition of an explosive mixtures e.g., dust-air mixtures, gas-(vapour-)air mixtures, dust-, gas-(vapour-)air mixtures and mists. In general explosion isolation systems are not designed to prevent the transmission of fire or burning powder either of which can initiate an explosion in downstream plant items. It is necessary to take this situation into account in risk assessments. This European Standard is only applicable for gas and dust explosions of chemically stable substances and mixtures of these (flame propagating at subsonic velocity).