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 order to address such restrictions, a new test method was derived, NFPA 286 Standard Methods of Fire Tests for Evaluating Contribution of Wall and Ceiling Interior Finish to Room Fire Growth.
This method is more indicative of real world fire hazards, and is preferred over NFPA 255,[4] but is more expensive.
UL 723 (ASTM E84) Test for Surface Burning Characteristics of Building Materials ASTM E84 - 15a Standard Test Method for Surface Burning Characteristics of Building Materials UL 94 Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances The Life Safety Code (NFPA 101)[5] and Section 803.1 of the International Building Code limit finishes for interior walls and ceilings to materials in three classes (A, B, or C, with A being the lowest flame spread and C being the highest) and gives greater restrictions for certain rooms: In order to meet classification in any of the three categories, the smoke developed index cannot exceed 450.