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test procedure exposes candidate materials in a horizontal, rectangular
tunnel 17 3/4" wide by 12" in height and 25 feet long. The tunnel is equipped
with two gas burners at one end that direct a flame onto the surface of
the test material under a controlled air flow. Flame spreads along the
surface of the material as the test progresses. Distance of the flame travel
and the rate at which the flame front advances during a 10 minute exposure
determine the calculated flame spread index.
To provide standard conditions
for each test, the tunnel is calibrated to an index of 0 for noncombustible
materials and 100 for 23/32" red oak flooring. Indices for tested materials
can range from 0 to over 1000.
Wood Products
Lumber, plywood, and other
wood-based materials exhibit a relatively narrow range of flame spread.
Differences result from factors such as density, thickness, surface characteristics
and chemical constituents. If the material is homogeneous, flame spread
may be considered nearly independent of material thickness at thicknesses
greater than 1/4".
Flame spread indices for
a number of species of lumber, plywood, particleboard, shakes and shingles
are listed in Table
1. In products such as softwood and hardwood plywood, the arrangement
and type of components may also influence surface flame spread. Some such
products are described by face species and core composition in Table
1. All ratings are based on the ASTM E-84 test method.
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| Flame
spread indices for a number of commercially available wood products with
factory applied overlay finishes are listed in Table
2. Factory finished wall panels are typically tested and labeled to
identify the flame spread classification of the finished product. Finish
composition, adhesive, and finish thickness may, however, affect flame
spread.
As can be seen from the listed
indices, most tested wood products have a flame spread index less than
200, making them acceptable under current building codes for a wide
range of interior finish uses. Flame spread indices for a range of proprietary
wood-based interior finish materials are also available from their manufacturers.
Commercially available fire retardant treatments for wood and panel products
can reduce flame spread performance to an index of 25 or less. Check with
the manufacturer for flame spread index.
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A
smoke-developed index was also measured for some of the wood products listed
in Table
1 and Table
2. This index also has a value of 100 for red oak. None of the products
tested exceeded 450, a limiting value commonly used in building code regulations.
| While
effort has been made to ensure the accuracy of the information in this
publication, the American Forest & Paper Association, and the Companies
and Associations identified, do not assume responsibility for the accuracy
of the indices reported, the applicability or extension of the reported
flame spread values to specific products, or their acceptance for use in
particular applications. |
Copyright © 1997-
2007
American Forest & Paper Association, Inc.
September 2007 Revisions |
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