The air permeability of cigarette paper is assessed currently under the ISO 2965 standard by applying a constant difference of pressure of 1 kPa between the two faces of a paper and by measuring the corresponding airflow.

Lower Ignition Propensity regulations have led tobacco manufacturers to use specific cigarette papers with narrow bands of low air permeability to achieve regulatory compliance. ISO 2965 was revised, then published in 2009 to take into account the specific geometry and characteristics of the bands and to include suitable narrow measuring heads. The consequence was a drastic reduction of the measured airflow levels with banded papers and a need for equipment covering specifically low airflow ranges.

The well-known pressure-airflow relationship across cigarette paper enabled the development of an alternative method to ISO 2965 not requiring direct airflow measurement, and then not requiring expensive airflow meters. In the alternative method, measurements are made of the evolution of the pressure over time after an initial difference of pressure was applied between the two faces, and to analyse consecutively the profile of pressure impacted by the leaks across the paper. The related theoretical aspects were developed for both viscous and inertial airflows, and experimental investigations were conducted with banded and standard cigarette papers.

Results showed very good consistency with ISO 2965 and lower repeatability, demonstrating that a leak-based method could be a simple, reliable and cheaper alternative.