In the early 1980s, CORESTA scientists agreed that a one and unique unit was needed worldwide to measure the air flow through various papers used in cigarette production, from the very low porosity cigarette papers to the very highly porous plug wraps, including the pre-perforated tipping papers that were increasingly used in cigarette design to bring filter ventilation in cigarettes.
Collaborative work including paper suppliers, porosity measurement devices producers, laboratories and cigarette manufacturers developed the CORESTA air permeability unit (CU) that is now commonly used in paper specifications by cigarette designers.
A CORESTA Unit is defined as:
"the volumetric flow rate of air (cm3 min-1)
passing through a 1 cm2 sample of substrate
at an applied pressure difference of 1 kPa"