Abstract / scope
ISO 5636-4:2005 specifies a method of determining the air flow rate through unit area of a sheet of paper or board, under unit pressure difference using apparatus called the Sheffield instrument.
The method is applicable to papers and boards having air permeances between 0,02 micrometres per pascal second and 25 micrometres per pascal second. The method is not suitable for papers and boards with a rough surface, such as crêpe paper and corrugated papers, which cannot be securely clamped to avoid surface leakage.