1 .l This part of IS0 4589 constitutes a guidance document for the 01 test. It provides information to guide the reader in the use of the test procedures described in parts 2 and 3. 1.2 Part 2 describes a method for determining the minimum concentration of oxygen by percentage volume in a mixture of oxygen and nitrogen introduced at 23 “6 + 2 “C that will just support combustion of a material under specified test conditions. The results are defined as 01 values. For comparative purposes, a procedure is also provided for determining whether or not the 01 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 pm and 100 pm thickness. 1.3 Part 3 describes methods of carrying out the same determination over a range of temperatures typically between 25 “C and 150 “C (although temperatures up to 400 “C may be used). The results are defined as 01 values at the test temperature. Part 3 also describes a method for determining the temperature at which the 01 of the small vertical test specimens is 20,9. The result is defined as the flammability temperature. Part 3 is not applicable to materials having an 01 value of less than 20,9 at 23 “C.