This part of ISO 5636 specifies the Sheffield method for determining the air permeance of paper and board using the Sheffield apparatus.

It is applicable to papers and boards which have air permeances between 0,02 µm/(Pa·s) and 25 µm/(Pa·s) when tested with the Sheffield apparatus.

It is unsuitable for rough-surfaced materials, which cannot be securely clamped to avoid leakage.