This European Standard identifies parameters that affect the fire resistance of ducts for ventilation purposes. It also identifies the factors that need to be considered when deciding whether, or by how much a parameter can be extended either positively or negatively when contemplating the fire resistance on an untested variation in the construction. This European Standard, where applicable, gives guidance on additional tests that are needed to extend the field of application.The European Standard gives the principles behind how a conclusion on the influence of specific parameters/constructional details relating to the relevant criteria (E, I, S) can be ach