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, i.e. all types of pedestrian and industrial doors and openable windows unless specifically excluded 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 door 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 door 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. Variations outside of the rules given in EN 1634-1 and EN 1634-3 for direct application require the consideration of agreed expert opinion and/or the interpolation and extrapolation from a series of tests in order to produce a field of extended application. The outcome of the agreed expert opinion provides the basis for the field of extended application derived from the rules provided in the relevant Part(s) of this series of standards.