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 476-7: 对建筑材料和结构的着火试验-第7部分：产品火焰表面延伸等级确定的测试方法。
测试方法是在燃烧箱内点燃烧样品，点燃源为燃气辐射板及中型燃气喷灯。辐射板的辐射强度在离75mm处为32.5kw/m2(表面),喷灯的火焰高75-100mm, 与辐射板在同一方向施加于试样。
样品暴露在辐射热源板下10min。记录1.5分钟及10分钟样品的火焰传播程度。测试结果分成4个等级，4级材料火灾危险性很高，不允许用为建材。
| Classification of spread of flame | ||||
| 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) |
| Class 1 | 165 | 165+25 | 165 | 165+25 |
| Class 2 | 215 | 215+25 | 455 | 455+45 |
| Class 3 | 265 | 265+25 | 710 | 710+75 |
| Class 4 | Exceeding the limits for class 3 | |||
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