This European Standard describes the general requirements for flap valves used for dust explosion isolation. An explosion isolation flap valve is a protective system, which prevents a dust explosion from propagating via connecting pipes or ducts into other parts of apparatus or plant areas. An explosion isolation flap valve can only stop the propagation of a dust explosion when it propagates against the direction of the normal process flow. It does not stop explosions running in the normal process flow direction. This European Standard specifies methods for evaluating the efficacy of explosion isolation flap valves. This European Standard is applicable only to explosion isolation flap valves which are intended to avoid explosion propagation from a vessel, into other parts of the installation via connecting pipes or ducts. The standard covers isolation of such vessels that are protected by explosion venting (including flameless venting), explosion suppression or explosion resistant design. NOTE 1 This standard is only applicable to cases where the explosion starts in a vessel and not in pipes or ducting. Explosion isolation flap valves are not designed to prevent the transmission of fire or burning powder transported by the normal process flow. NOTE 2 It is necessary to take this into account in risk assessments. This European Standard is only applicable for dust explosions. This European Standard is not applicable for explosions of materials listed below, or for mixtures containing some of those materials: gases, vapours and hybrid mixtures; chemically unstable substances; explosive substances; pyrotechnic substances.