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BS 6853/BS 476-7: Classification of spread of flame
BS 476-7: Fire tests on building materials and structures-Part 7 method of test to determine the classification of the surface spread of flame of products.
BS 6853/BS 476-7 test method
The specimen is mounted in a water-cooled holder and is exposed to a radiant panel over a ten minute test duration. In addition, a pilot flame is applied to the bottom corner of the specimen during the first minute of test. The time required for the flame front to reach reference marks on the specimen is noted, together with the extent of flame spread at one minute thirty seconds test duration and at the end of the test. Observations are also made of the burning behaviour.
Materials are classified according to test performance as shown in the table below. Class 1 is the best classification that can be achieved during this test alone and Class 4 is the worst classification that can be achieved on this test. Class 4 materials are considered high risk.
BS 6853/BS 476-7:1997 classification Evaluate
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Classification of spread of flame |
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Classification |
Spread of flame at 1.5 min |
Final spread of flame (10 min) |
|
|
Limit (mm) |
Limit for one specimen in sample (mm) |
Limit (mm) |
Limit for one specimen in sample (mm) |
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Class 1 |
165 |
165+25 |
165 |
165+25 |
|
Class 2 |
215 |
215+25 |
455 |
455+45 |
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Class 3 |
265 |
265+25 |
710 |
710+75 |
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Class 4 |
Exceeding the limits for class 3 |
BS 6853:1999 standard requirement
Worst Classification requirement: Class 2, allows Classification: Class 1 or Class 2
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Testing to：
Fire standard
