The spread of flame is measured along the sides of a vertical or horizontal surface of a specimen exposed to a flame and a radiant panel. The after-glow, damaged zone and dripping are also observed.
The radiant panel and pilot flame are ignited. The burner and the vertically oriented specimen are then positioned. The time to reach the different marker threads is recorded. The average velocity is calculated to reach the flame spread velocity. The damaged zone and dripping and flaming debris are observed. Based on the observations of flame spread, damaged zone and dripping and flaming debris, the material can be classified in levels.
The levels are multiplied with a factor. Flame spread velocity x2, Damaged zone x2, After-glow time x1, Dripping x1 for wall and x2 for ceiling. The sum of the levels of behaviour multiplied by the correction factors give the products category (I to IV).