ISO 4589-2:20 17规定了测定氧气与氮气混合的最小体积分数的方法，该方法将支持小型垂直试样在指定测试条件下的燃烧。结果被定义为氧指数(OI)值。 提供了用于测试厚度达10.5 mm的垂直杆或片材形式的自支撑材料的方法。这些方法适用于表观密度为100kg/m3或更大的固体、层压或多孔材料。所述方法还可适用于表观密度小于100kg/m3的一些多孔材料。提供了一种在垂直支撑时测试柔性片材或薄膜材料的方法。 为了比较的目的，提供了用于确定材料的OI是否高于某个指定的最小值的过程。

ISO 4589-2:2017 specifies methods for determining the minimum volume fraction of oxygen, in admixture with nitrogen, that will support combustion of small vertical test specimens under specified test conditions. The results are defined as oxygen index (OI) values. Methods are provided for testing materials that are self-supporting in the form of vertical bars or sheets up to 10,5 mm thick. These methods are suitable for solid, laminated or cellular materials characterized by an apparent density 100 kg/m³ or greater. The methods might also be applicable to some cellular materials having an apparent density of less than 100 kg/m³. A method is provided for testing flexible sheets or film materials while supported vertically. For comparative purposes, a procedure is provided for determining whether or not the OI of a material lies above some specified minimum value.