In the United states and Canada fire tests are commonly conducted in accordance with the provisions of ASTM E 119: Standard Methods of Fire Tests of Building Construction and Materials. ASTM E 119 was formulated to provide a uniform way to assign comparative ratings to the performance during a fire of such construction assemblies as composite floors, wall panels, roofs, beams, and columns. The ultimate aim is to encourage the design and construction of structures that are safe, do no constitute a hazard to neighboring buildings or to human life and offer a reasonable degree of protection to firemen and fire fighting equipment. Without going into great detail, a standard fire test is conducted in the following way. The wall, floor, or roof assembly (with thermocouples at a minimum of nine locations on its unexposed surface) is placed in a test furnace in a manner that subjects one of its surfaces to the heat prescribed by the test method. The temperature is then raised a 1,000 degrees F in the first five minutes of the test, to 1,300 degrees F by 10 minutes, 1,550 degrees F by one-half hour, 1,700 degrees F by the first hour, and to 2,000 degrees F in four hours. The temperature at eight hours or longer is 2,300 degrees F. A test is discontinued when one of the following things occurs: the unit no longer supports the load; flames or gases in sufficient volume and heat intensity to ignite cotton wastes; or transmission of heat through the unit is such that the average unexposed surface temperature rises by more than 250 degrees F. Fire ratings are generally assigned according to the last full hour successfully achieved under test conditions. Thus, normally if a floor slab fulfilled test conditions successfully for three hours 58 minutes it would be give a three hour rating.