SYMPOSIA PAPER Published: 01 January 1963

Surface Flammability as Determined by the FPL 8-FT Tunnel Method


One of the more commonly accepted methods for measuring the surface flammability of materials is to observe the flame movement when the test specimen is exposed as the upper horizontal surface of a tunnel furnace. The large tunnel furnace (ASTM Method E 84) uses this method, but because of the large size of the furnace and specimen, its use is considered impractical in many instances, especially for research and development purposes. Therefore, a small tunnel furnace to measure flame spread was developed by the U. S. Forest Products Laboratory in cooperation with both the Housing and Home Finance Agency and ASTM Committee E-5 on Fire Tests of Materials and Construction. The resulting 8-ft tunnel furnace uses a specimen 14 in. wide and 8 ft long, the plane of which is positioned from the horizontal at an angle of 30 deg across the short dimension, and 6 deg along the long dimension, so the test can be performed under natural draft conditions. Heat to induce flaming is supplied by a radiant metal plate below the specimen and by a small ignition flame applied directly against the lower end of the specimen. Order of ranking of the surface flammability of untreated wood products by the small tunnel is generally the same as by the ASTM E 84 tunnel test. However, for fire-retardant treated and coated materials in which flaming is very weak, the direct correlation of index values is not good because the 8-ft tunnel usually produces the higher flame-index values. Six 8-ft tunnel furnaces, in addition to the one at the Forest Products Laboratory, are currently in use in research laboratories.

Author Information

Peters, C
Forest Products Laboratory, Forest Service, U. S. Department of Agriculture, Madison, Wis.
Eickner, H
Forest Products Laboratory, Forest Service, U. S. Department of Agriculture, Madison, Wis.
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Developed by Committee: E05
Pages: 18–32
DOI: 10.1520/STP44503S
ISBN-EB: 978-0-8031-5987-7
ISBN-13: 978-0-8031-6141-2