This part of prEN 15269 sets out the general principles for the extended application of test results obtained on fire resisting and smoke control doorsets including their elements of building hardware, i.e. the types of pedestrian and industrial doors and openable windows listed in the Introduction above when tested in accordance with EN 1634-1 and/or EN 1634-3. This document provides the general principles which are intended to be used in conjunction with the relevant Part of EN 15269 depending upon the specific product type to be evaluated. The rules to evaluate the field of direct application of fire resisting or smoke control door, shutter and openable window assemblies are given in EN 1634-1 or EN 1634-3 respectively and are based on the results of a single test. These relate to the more common forms of product constructions for which experience of testing has provided the knowledge that such variations can be safely accepted. The extent of the permitted variations is generally conservative and is based on the minimum level of common agreement achieved. This part of the prEN 15269 series of standards identifies the principles to be followed during the preparation of the subsequent product related parts of this standard which define the rules for the permitted variations of products from the tested specimen. These rules created in committee by agreed expert opinion, based on experience of fire testing and interpolation of test results, will form the basis of the field of extended application. When these rules are applied by a body suitably notified for the purpose, they will lead to a classification suitable for the application of a CE mark to the modified product.