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Flame
Spread
When
evaluating building materials for fire safety, many
factors including ignition temperature, smoke
toxicity and flame-spread are considered.
Flame-spread, used to describe the surface burning
characteristics of building materials, is one of the
most tested fire performance properties of a
material. The best known test for developing this
rating is the American Society for Testing and
Materials (ASTM) Test Method E-84, commonly known as
the tunnel test.
The tunnel test measures how far and how fast
flames spread across the surface of the test sample.
In this test, a sample of the material 20 inches
wide and 25 feet long, is installed as ceiling of a
test chamber, and exposed to a gas flame at one end.
The resulting flame spread rating (FSR) is expressed
as a number on a continuous scale where inorganic
reinforced cement board is 0 and red oak is 100.
The scale is divided into three classes. The most
commonly used flame-spread classifications are:
Class I or A, with a 0-25 FSR; Class II or B with a
26-75 FSR; and Class III or C with a 76-200 FSR.
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Comparison
between each material
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Materials
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FlameSpreadRating
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Flame-Spread
Class
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"Sunny"
Inorganic Fire Proof Board
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0
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I
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Hardboard
siding panels
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<200
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III
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APA
Wood Structural Panels (includes APA 303
Sidings such as T1-11)
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76-200
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III
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Birch,
Yellow
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80
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III
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Brick
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0
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I
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Cedar,
Western Red
|
69
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II
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Douglas-fir
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90
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III
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Fiberboard,
Medium Density
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167
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III
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Gypsum
Wallboard
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10-15
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I
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Gypsum
Sheathing
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15-20
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I
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fiber-cement
exterior materials
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0
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I
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Hemlock,
West Coast
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73
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II
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Idaho
white pine
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82
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III
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Maple
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104
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III
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Masonite
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<200
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III
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Oak,
Red or White
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100
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III
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Oriented
Strand Board (OSB)
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150
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III
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Particle
Board
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116-178
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III
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Pine,
Lodgepole
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98
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III
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Pine,
Ponderosa
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115
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III
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Plywood,
Fire-retardant-treated construction
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0-25
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I
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Plywood,
Oak
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125-185
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III
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Plywood,
Pine
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120-140
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III
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Spruce,
Engelmann
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55
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II
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