Flammability耐燃等級 - Materials may be classified based on burning tests conducted in accordance with Underwriters Laboratories Inc. Standard Tests For Flammability of Plastic Materials For Parts In Devices and Appliances, UL 94. By small-scale tests, materials are classified as V-0, V-1, V-2, HB, VTM-0, VTM-1, VTM-2, HF-1, HF-2, or HBF. In addition, some materials may also secondarily be classified as 5VA or 5VB. Materials may also be evaluated using the radiant panel in accordance with ASTM E-162 (referenced in UL94); such flame spread indices are shown as "RP25", "RP100", etc. UL94 small-scale test data does not pertain to building materials, furnishings and related contents. UL94 small-scale test data is intended solely for determining the flammability of plastic materials used in the components and parts of end-use product devices and appliances, where the acceptability of the combination is determined by UL Inc.

In addition, some materials have been subjected to Fire Tests in accordance with Underwriters Laboratories Inc. Standard Test Method for Surface Burning Characteristics of Building Materials, UL723 which provides data concerning (1) flame spread, (2) fuel contributed, and (3) smoke developed. For the classification of building materials, see "Building Materials Directory".