What Is Oxygen Index?

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Oxygen index refers to the lower limit of oxygen concentration required for the sample to maintain stable combustion in the mixed flow of oxygen and nitrogen under specified conditions, which is expressed by the volume percentage of oxygen to nitrogen mixture. Oxygen index was measured by oxygen index meter. Oxygen index is a method to evaluate the flammability of plastics and other polymer materials. Because our atmosphere contains only 21% oxygen, that is, the oxygen index is 21. When the oxygen index of the material is greater than 26%, it can not be burned in the ordinary air, that is, it is difficult to burn. Therefore, it is generally considered that the oxygen index 22 belongs to the flammable material, the oxygen index between 22 and 27 belongs to the combustible material, and the oxygen index 27 belongs to the refractory material. According to the 97 edition of classification method for flammability of building materials, the oxygen index of Class B1 (refractory materials) is ≥ 26; that of grade B2 (combustible materials) is ≥ 32.

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