Defines the general requirements for the oxygen index (OI) test which are further described in ISO 4589-2 and ISO 4589-3 as follows: - ISO 4589 2 describes a method for determining the minimum volume fraction of oxygen in a mixture of oxygen and nitrogen introduced at 23 degrees C +/- 2 degrees C that will just support combustion of a material under specified test conditions; - ISO 4589-3 describes methods of carrying out the same determination over a range of temperatures typically between 25 degrees C and 150 degrees C (although temperatures up to 400 degrees C can be used).