Polyester has a better behavior against inflammability compared to cellulous natural fibers. Polyester has an ignition temperature of 450 to 560°C. When ignition happens, the exposed area is turned to charcoal and fused. Cellulous natural fibers have an ignition temperature of 400°C. The fabrics burn and spread the flame with residual white heat. Combustion behavior: the most common synthetic fibers are acrylics and thermoplastics like polyester. Thermoplastics generally don’t turn to charcoal; they contract and burn out. Spreading of fire is slow. The molten polymers flow downwards, making the flames move laterally and in a descending way or make tears that may or may not burn. Compared with natural fibers, thermoplastics are harder to set on fire and the flames cover smaller areas, spread slowly, and burn out on their own. However, there are some cases in which the thermoplastic fibers burn rapidly. This happens when the fibers have been covered or died with dense colors and they lose their capacity to burn without flames. Natural fibers turn to charcoal but they don’t melt.