What is the test method for flame spread?
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.
