1.1 This Part of GB/T 2406 constitutes a guidance document for the OI test. It provides information to guide the reader in the use of the test procedures described in ISO 4589-2 and ISO 4589-3.
1.2 ISO 4589-2 describes a method for determining the minimum concentration of oxygen by percentage volume in a mixture of oxygen and nitrogen introduced at 23 ℃ ± 2 ℃ that will just support combustion of a material under specified test conditions. The results are defined as OI values. For comparative purposes, a procedure is also provided for determining whether or not the OI of a material lies above some specified minimum value which is particularly important for quality control purposes. There is also a procedure for the testing of thin films between 20 μm and 100 μm thickness.
1.3 ISO 4589-3 describes methods of carrying out the same determination over a range of temperatures typically between 25 ℃ and 150 ℃ (although temperatures up to 400 ℃ may be used). The results are defined as OI values at the test temperature. ISO 4589-3 also describes a method for determining the temperature at which the OI of the small vertical test specimens is 20.9. The result is defined as the flammability temperature. ISO 4589-3 is not applicable to materials having an OI value of less than 20.9 at 23 ℃.
