Test steps: 1. Take out the pre treated sample, place the surface fuzzed or tufted sample flat on a flat surface, and use a specified metal comb to comb twice along the opposite direction of the fuzz on the fuzzed surface. Ignite the gas lamp with the air inlet closed and adjust the flame according to the flame height indicator plate to a flame height of 38mm. Before starting the * test, the flame should burn steadily in this state for at least 1 minute before extinguishing. Mount the exposed surface of the specimen into the specimen holder facing downwards. Install the specimen so that both sides and one end are clamped by a U-shaped bracket, and the free end aligns with the opening of the U-shaped bracket. When the width of the sample is insufficient, the U-shaped bracket cannot grip the sample, or the free end of the sample is soft and prone to bending, which can cause unstable combustion, the sample should be placed on the sample bracket with heat-resistant metal wire for combustion testing 2. Push the sample holder into the combustion chamber, place the sample in the center of the combustion chamber, and place it in a horizontal position. Ignite the gas lamp with the air inlet closed and set the flame height to 38mm, allowing the free end of the sample to ignite in the flame for 15 seconds, and then extinguish the flame (close the gas lamp valve). The flame burns forward from the free end of the sample and starts timing at the moment when the flame propagates through the * marking line at the root. Pay attention to the flame propagation on the side that burns faster, and the timing should be based on the side that spreads faster When the flame reaches the second marking line or extinguishes before reaching the second marking line, the timing shall also be stopped, and the timing shall be based on the side where the flame propagates faster. If the flame extinguishes before reaching the second marking line, measure the burning distance from the * marking line until the flame extinguishes. The burning distance refers to the length of the burned part on the surface or inside of the sample If the non exposed surface of the sample is cut, the timing should be based on the flame propagation speed of the exposed surface. The requirement for combustion speed does not apply to the surface formed by cutting the specimen. If the sample burns slowly for a long time starting from the timing, the test can be stopped at a time of 20 minutes and the burning time and distance can be recorded. When conducting a series of tests or repeating tests, the high temperature in the combustion chamber and sample holder before the next test should not exceed 30 ℃