Specifies methods for the determination the minimum concentration 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 °Celsius and 150 °Celsius. The results are defined as oxygen index values at the test temperature. Also included is a method for determining the flammability temperature (less than 400 °Celsius) at which the oxygen index of small vertical test specimens in air is 20,9.