flame-spread index

flame-spread index

A numerical designation, applied to a building material, which is a comparative measure of the ability of the material to resist flaming combustion over its surface; the rate of flame travel, as measured under the applicable ASTM test, in which a selected species of untreated lumber has a designated value of 100, and noncombustible cement-asbestos board has a value of 0.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.