ISO 5636-5:2013 specifies the Gurley method for determining the air permeance of paper and board using an air resistance tester, the Gurley apparatus. It is applicable to papers and boards which have air permeances between 0,1 µm/(Pa⋅s) and 100 µm/(Pa⋅s) when tested with the Gurley apparatus. It is unsuitable for rough-surfaced materials, which cannot be securely clamped to avoid leakage. ISO 5636-5:2013 may also be used to determine the air resistance of paper and board.