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L Flame Spread Index for Wnnd Products Fire Safety of Wood Products USDA, Forest Service Forest Products Laboratory One Gifford Pinchot Drive Madison,WI 53705-2398 Numerous flame-spread tests are used, but the most common one cited by building codes is ASTM E 84,the 25-foot tunnel test. This test method involves the use of a 20-inch by 25-foot specimen exposed horizontally to a furnace operating under forced draft conditions.The two results of this test are the flame spread index and smoke developed index. In the past,select grade red oak flooring was used as a standard and was given a flame spread index of 100.Today,red oak flooring still has an index around 100 but is no longer used in the calculation of the flame spread index.The smoke developed index is still based on red oak flooring having a value of 100.The indexes are els]based on inorganic reinforced cement board having a value of zero. For regulatory purposes, interior finish materials are classified according to their flame spread. The classes are 0-25 for Class A or I,26-75 for Class B or II, and 76-200 for Class C or III. For regulatory purposes,the requirement for smoke developed index is usually 450 or less. This list of ASTM F 84 flame spread indexes and smoke developed indexes for untreated wood products was prepared from the literature.The Forest Products Laboratory(FPL)does not have ` an ASTM E 84 test furnace. Results from the 8-foot tunnel(ASTM E 286)of the FPL are not comparable or equivalent to ASTM E 84 test results A list of commercial testing laboratories with the 25-foot tunnel is available from the Fire Safety of Wood Products Research Work Unit(608- 264-5669). The flame spread index may depend on density,thickness,chemical composition, and surface characteristics. Finishes on the wood may affect the flame spread index depending on the thickness and composition of the finish.Changes in the procedures for calculating the flame spread index have also affected the numbers. Species identification on this list are the names given in the references. Exact identification of the species may not have been possible. Fire-retardant treatments can be used to reduce the flame spread index of wood to 25 or less. Lists of the fire-retardant coatings and pressure testers are also available from the Fire Safety of Wood Products Research Work Unit. Building code officials may require building materials to be stamped with the flame spread classification of an approved testing agency. Users should consult the manufacturer as to the availability of their product with an approved stamp. L