ASTM E119 is the most important fire testing standard in US construction. It establishes the time-temperature curve and test procedures for determining fire-resistance ratings of building elements. Standard time-temperature curve: 1000°F at 5 minutes, 1300°F at 10 minutes, 1550°F at 30 minutes, 1700°F at 1 hour, 1850°F at 2 hours, 2000°F at 4 hours. Pass criteria: (1) structural integrity — specimen carries applied load throughout test, (2) flame passage — no through openings develop, (3) temperature rise — unexposed surface average temperature rise does not exceed 250°F. Test specimens are full-scale assemblies. Results are expressed in hours: 1-hour, 2-hour, 3-hour, 4-hour ratings. UL maintains the largest directory of tested assemblies (UL Fire Resistance Directory). Assembly numbers (e.g., U305, W419) are the industry standard for specifying fire-rated construction.