All fabrics of natural or regenerated cellulose, as well as certain types of finished and unfinished fabrics made from other natural or synthetic fibers, are combustible. Some combustible fabrics are potentially dangerous to the wearer because of the speed and intensity of flame with which these fabrics burn and their ease of ignition. Flammability test measures how easily materials ignite, how quickly they burn and how they react when burned. Many countries have flammability requirements establishing guidelines that PPE products must meet. https://www.ste-mart.com/flammability-test.htm