The purpose of this standard is to specify the method to be used to determine the resistance offered by a sheet of paper or cardboard to the passage of air through it. This method is applied to papers and cardboard that, in accordance with the conditions specified below, allow the passage of 100 cm3 of air in a period of time between 5 and 1 800 s. It is not usable for papers with a rough surface, such as creped or corrugated papers that, since they cannot be adequately fixed in the clamping device of the device, allow air to escape laterally.