Understanding Flame Spread Ratings
11/13/2012 | Dunn Edwards |
The ICC International Building Code (for new buildings) and International Fire Code (for existing buildings) limit the allowable flame spread and smoke development characteristics of building materials used for interior finishing, based on location and occupancy type. Materials are grouped in the following classes by Flame Spread Index and Smoke Developed Index when tested in accordance with ASTM Method E 84, “Standard Test Method for Surface Burning Characteristics of Building Materials”:
Material classes | ||
---|---|---|
Class A: | Flame Spread Index | 0 – 25 |
Smoke Developed Index | 0 – 450 | |
Class B: | Flame Spread Index | 26 – 75 |
Smoke Developed Index | 0 – 450 | |
Class C: | Flame Spread Index | 76 – 100 |
Smoke Developed Index | 0 – 450 |
Exceptions include exposed portions of structural members that meet other requirements, and materials having a thickness less than 0.036 inch (36 mils) applied directly to the surface of walls or ceilings. Standard interior paints and coatings are typically applied to produce dry films of 1 to 2 mils per coat.
What are Flame Spread and Smoke Developed Indexes? Flame Spread Index This is determined by the distance that a flame travels along a test substrate in a limited time, compared to inorganic reinforced cement board, which is rated 0, and select grade red oak flooring, which is assigned an arbitrary rating of 100. Smoke Developed Index This is determined by the concentration of smoke that a test substrate emits as it burns, again compared to inorganic reinforced cement board, which is rated 0, and select grade red oak flooring, which is assigned an arbitrary rating of 100.
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