This Technical Report refers to prEN 16798-3. It contains information to support the correct understanding and use of this standard. This Technical Report does not contain any normative provision. This Technical Report applies to the design and implementation of ventilation, air conditioning and room conditioning systems for non-residential buildings subject to human occupancy, excluding applications like industrial processes. It focuses on the definitions of the various parameters, which are relevant for such systems. The guidance for design given in this standard and its annexes are mainly applicable to mechanical supply and exhaust ventilation systems, and the mechanical part of hybrid ventilation systems. Furthermore general design principles of natural ventilation systems are introduced in Annex D. Applications for residential ventilation are not dealt with in this technical report. Performance of ventilation systems in residential buildings are dealt with in CEN/TR 14788. The classification uses different categories. For some values, examples are given and, for requirements, typical ranges with default values are presented. The default values given in this standard are not normative as such, and should be used where no other values are specified. Classification should always be appropriate to the type of building and its intended use, and the basis of the classification should be explained if the examples given in the standard are not to be used. NOTE Different standards might express the categories for the same parameters in a different way, and the category symbols may be different.