This International Standard provides general principles for a performance-based methodology for engineers to assess the level of fire safety for new or existing built environments. Fire safety is evaluated through an engineered approach based on the quantification of the behaviour of fire and people and based on knowledge of the consequences of such behaviour on life safety, property and the environment. This International Standard is not intended as a detailed technical design guide, but does contain the key elements needed by practicing fire safety engineers and peer reviewers (those entities who can be required to review the work of fire-safety engineers) for addressing the different steps and their linkages in a design process. The information contained in this International Standard is intended not only to be useful to engineers directly but also to serve as a template to guide the development of a consistent set of fire-safety engineering documents covering the role of engineering methods and test methods in performance-based design and assessment. The basic principles of fire-safety design and related fire-safety objectives in this International Standard can be applied in any other document addressing phenomena associated with fire (e.g. fire growth, hot gases and effluents movement, structural and compartmentalization behaviour). Related fire-safety objectives include, for example, — safety of life; — conservation of property; — continuity of operations; — protection of the environment; — preservation of heritage. Furthermore, these basic principles can be applied to all configurations of the built environment (e.g. buildings, transportation systems and industrial installations). Because prescriptive regulations covering fire-safety design will co-exist for some time with performance-based design, this International Standard takes into account that fire-safety designs conforming to prescriptive regulations can become the basis for comparison of engineered designs of new built environments.