NFPA 255
===Significance and Use===
Standard Method of Test of Surface Burning Characteristics of Building Materials, utilizes ASTM E84 Standard Test Method for Surface Burning Characteristics of Building Materials. This test method measures flame growth on the underside of a horizontal test specimen. The result is derivation of a Flame Spread Index (FSI)[2], which is a non-dimensional number which is placed on a relative scale in which asbestos-cement board has a value of 0, and red oak wood has 100. Evaluation of a FSI by this test method does not provide a good understanding of how fire would propagate in full scale, such as in a room, for some materials. In particular, the results for materials that drip, such as thermoplastics, are not indicative of the fire hazard as installed on walls and ceilings because they tend to melt and drip away from the underside of the horizontal ceiling in the test chamber. Because the test method measures how far down the test chamber the fire progressed, this type of "lack of fire progression" provides a misleading FSI. [1]
