A Model Study on the Diffusion and the Dilution of Low Molecular Weight Gaseous Components through Cigarette Paper during Smoking

The effects of diffusion and dilution on the concentration of gaseous components have been studied by a model consisting of unlit cigarettes differing in paper porosity and length, and a standard gas mixture. Results are as follows: The difference in the concentration of gaseous components between the front and butt end of the cigarette during the puff increases with cigarette length and paper porosity, and also depends on the diffusion coefficient of respective components through the cigarette paper. These changes could be explained mainly by the diffusion loss through the paper in the case of the cigarette with ordinary paper, but by both dilution with air through the paper and diffusion loss in the case of the cigarette with perforated paper. Subsequently, the levels of gaseous components such as carbon monoxide in the exit stream become lower in the Iatter cigarette. In addition, the following equation, which can fully account for these changes, has been derived:

where C1i and C0i are the concentrations of the component i at the front and butt end, respectively, L the cigarette length, r the cigarette radius, s the thickness of paper, U0 and U1 the apparent linear gas velocities at the butt and front end, respectively, and Di the diffusion coefficient of component i through the paper.