Fire scenarios in process industry have a high potential to cause severe asset damage. Fireproofing is a consolidated technique for passive fire protection for units and supporting structures. Since several materials are available for passive fire protection, it is important to choose the best solution for the protected equipment and critical fire scenarios. Current practice in rating fireproofing materials does not provide sufficient information about the protection granted to process equipment: for example, the ‘time-to-failure’ of pressurized vessels protected by fireproofing materials cannot be predicted from the results of standardized fire tests. This study investigates the key properties (e.g. density, geometrical structure, thermal degradation and thermal conductivity) of representative fireproofing materials, in order to better understand the elements underlying the actual protection performance. An experimental activity was focused on the definition of fundamental models to describe the thermo-physical properties of the materials. The investigation cast the foundations of a better understanding of the dynamics underlying the effective design for passive fire protection, identifying the criticalities and limits of the alternative fireproofing options. The changes in the physical properties of materials during fire exposure were confirmed to play a major role on the protection performance. Such effects could not be accounted for complex geometries by conventional simplified approaches alone: thus, the proposed approach paves the way for a safer and more cost effective design of passive fire protection systems.