This part of ISO 4589 specifies methods for determining the minimum volume fraction of oxygen, in a mixture with nitrogen, that will support combustion of small vertical test specimens under specified test conditions over a range of temperatures between 25 °C and 150 °C. The range of temperatures is typically between 40 °C and 150 °C. The results are defined as temperature index values at the test temperature, which is typical of the practical temperature that a plastic material may experience in an overheated service situation. Methods are provided for testing materials that are self-supporting at the test temperature in the form of vertical bars or sheet up to 10,5 mm thick. However, they are not applicable to form V which requires supporting frame as defined in Table 2 of Part 2. These methods are suitable for solid, laminated or cellular materials characterized by an apparent density 100 kg/m3 or greater. The methods may also be applicable to some cellular materials having an apparent density of less than 100 kg/m3. A method is provided for testing flexible sheet or film materials while supported vertically. This part of ISO 4589 also includes a method (see Annex A) for determining the temperature at which the oxygen index of small vertical test specimens in air is 20,9 % under specified test conditions. The temperature at which this occurs is defined as the flammability temperature (FT) and the method is limited to the determination of temperatures less than 400 °C. The method is not applicable to materials having an oxygen index of < 20,9 %. Results obtained in accordance with this part of ISO 4589 is not applicable to describe or appraise the fire hazard presented by a particular material or shape under actual fire conditions, unless used as one element of a fire risk assessment which takes into account all of the factors which are pertinent to the assessment of the fire hazard of a particular application for the material. NOTE 1 It may not be possible to apply these methods satisfactorily to materials that exhibit high levels of shrinkage when heated, e.g. highly oriented thin film. NOTE 2 For assessing the flame propagation properties of cellular materials of density < 100 kg/m3, attention is drawn to the method of ISO 3582:2000, Flexible cellular polymeric materials çø Laboratory assessment of horizontal burning characteristics of small specimens subjected to a small flame.