This standard test method is used throughout the United States of America as well as other countries that may have adopted this standard. Several standard test methods are similar or identical to the ASTM E119 code, including the “UL 263, UBC 7-1, NFPA 251, and ANSI A2.1” (4). This test uses a standard time-temperature curve to measure the fire resistance of a constructed wall, floor, roof, or partition system. The standard also includes methods to test load or non-load bearing assemblies. A hose stream test can be performed on a test assembly when finished, which tests the if the sample remains intact after being exposed to elevated temperatures. https://sourceforge.wpi.edu/sf/wiki/do/viewPage/projects.fp570_ab06/wiki/FireResistanceOfSteel
Fire resistive products used to protect commercial hi-rise buildings are tested to ASTM E119. This standard requires that the fire resistive product protects the steel from reaching a limiting temperature during the time period required by the building codes. For the structural frame (columns and primary beams) the time period is 3 hours and the limiting temperature is 1200 F at any measured point on the column. For the primary beams the limiting temperature is 1300 F at any measured point on the beam. Floor beams require the same limiting temperature, but the time period is reduced to 2 hours.
The test furnace follows a temperature curve so that the test specimen is exposed to a temperature of 1550 F at 1/2 hour, 1700 F at 1 hour 1850 F at 2 hours, 1960 F at 3 hours, and 2000 F at 4 hours. In other words under this test a fire resistive product with a 3 hour column rating, the highest temperature it was exposed to was 1960 F and only towards the end of the test.
On the other hand, fire resistive products used to protect refineries, petrochemical plants, etc, against hydrocarbon fires are tested to UL 1709. This standard requires that the test furnace reaches 2000 F in 5 minutes. Under this test then, the fire resistive product with a 3 hour column rating has been exposed to a temperature of 2000 F for 2 hours 55 minutes. http://web.archive.org/web/20011121115318/http://www.engr.psu.edu/ae/WTC/MannyHerraResponse.htm