ISO 5636-5:2003 specifies the Gurley method of determining the air permeance of paper and board. It is applicable to papers and boards which have air permeances between 0,1 micrometres per pascal second and 100 micrometres per pascal second. It is unsuitable for rough-surfaced materials, which cannot be securely clamped to avoid leakage. This method may also be used to determine the air resistance of paper and board.