The principle consists in heating the test portion in the specified apparatus. The ignition trial is carried out after the test portion has been maintained under equilibrium conditions for 60 s at the selected equilibrium temperature. This procedure ensures that air/vapour space above the test portion has attained the saturation concentration of flammable vapour before the ignition trial is performed. This method of test does not determine the flashpoint of the product under test, but merely its behaviour at the selected equilibrium temperature as may be required to comply with or regulations.