ISO/TR 15656:2003 provides guidance for evaluating the predictive capability of calculation models for structural fire behaviour. It is specific to models that are intended to predict the fire resistance or fire endurance of structural members or assemblies. Such models include models simulating the thermal behaviour and mechanical behaviour of fire-exposed load-bearing and/or separating structures and structural elements.

In ISO/TR 15656:2003, the term model includes all calculation procedures that are based on physical models. These mechanistic-based or physical models encompass all the physical, mathematical and numerical assumptions and approximations that are employed to describe the behaviour of structural members and assemblies when subjected to a fire. In general, such physical models are implemented as a computer code on a digital computer. The application and extension of results from calculation methods are generally limited to performance resulting from standard tests. Aspects of ISO/TR 15656:2003 are applicable to calculation procedures not based on physical models. Mechanistic-based models can often be used to calculate the behaviour of structures in non-standard fire exposures.

The process of model evaluation is critical in establishing both the acceptable uses and limitations of fire models. It is not possible to evaluate a model in total; instead, ISO/TR 15656:2003 is intended to provide methodologies for evaluating the predictive capabilities for specific uses. Documentation of suitability for certain applications or scenarios does not imply validation for other scenarios.