The concept of 'traveling fires' in large enclosures, which assist with structural fire analysis, is discussed. These fires represent a new understanding of fire behavior in modern building layouts. Fire scenarios currently used for the structural fire design of modern buildings are based on traditional methods that come from the extrapolation of existing fire test data. This test geometry allows for good mixing of the fire gases and thus for a uniform temperature distribution throughout the compartment. The standard fire came from collating various fire tests into one idealized curve. A traveling fire can therefore inflict the structure with elevated temperatures for longer durations. The traditional design methods for thermal inputs for structural analysis are known to be valid for small enclosures.