A review of thermal exposure and fire spread mechanisms in large outdoor fires and the built environment

Due to socio-economic and climatic changes around the world, large outdoor fires in the built environment have become one of the global issues that threaten billions of people. The devastating effects of them are indicative of weaknesses in existing building codes and standard testing methodologies. This is due in part to our limited understanding of large outdoor fire exposures, including the ones from wildland to communities and within communities. To address this problem, the Ignition Resistance Committee (IRC) of the International Association of the Fire Safety Science working group 'Large Outdoor Fires and the Built Environment' was established. This manuscript is the result of one of the IRC's initiatives to review current knowledge on exposures associated with large outdoor fires, identify existing knowledge gaps, and provide recommendations for future research. The article consists of two sections: the wildland fire exposure to the built environment and the settlement fire exposure to structures. Each section presents a comprehensive review of experimental and numerical studies of exposure mechanisms (flame contact and convection, radiation, and firebrands). The review concludes with a discussion on data consistency and existing knowledge gaps to highlight future directions for each of the three fire exposure mechanisms.