Potential Sources of Measurement Error When Measuring the Permeability of Low Ignition Propensity (lip) Papers to Iso 2965

Measurement of permeability of cigarette envelope papers used in Low Ignition Propensity (LIP) cigarettes presents a number of practical problems:  Measurements must be made on both the conventional and low permeability band regions.  The low permeability band must be measured using a small orifice (15 x 2 mm compared to the normal 20 x 10 mm) with a flow as low as 1 ml/minute.  Leakage from the periphery of the paper – both between the paper and clamp face and laterally through the paper – is more significant as the orifice to perimeter ratio increases, which can offset permeability values obtained on the same paper when different orifice sizes are used. The effect of measuring cigarette papers using 2 orifice sizes has been quantified by combining two orifices into a single clamp and enabling both vacuum and pressure measurements. Through measurement without needing to invert papers this procedure has enabled a direct measurement of flow asymmetry for banded papers, which was found not to be significant. To provide a means of validating measurement accuracy for the two orifice sizes, aluminized plastic with a fine pin hole was used to provide a constant flow without peripheral leakage. As much as 20% of measured flow from the small orifice on banded papers could be ascribed to the periphery. Recommendations are made to reduce inconstancies in comparisons between paper types and improve reliability of measurement of LIP papers.