Effects of cigarette circumference on cigarette ventilation rate during smoking
Cigarette ventilation is one of the key parameters during cigarette design, that strongly affects cigarette combustion behaviour and the smoke components released. When combustion occurs, smoke is produced and transferred from the cut tobacco to the filter. Air viscosity, moisture and other parameters along the cigarette axial direction are altered compared with the unburned cigarette. There are few studies characterizing the instantaneous ventilation of a burning cigarette due to the rapid change during combustion. The purpose of this study was to develop a simple and accurate method to determine the puff-by-puff ventilation along the axial direction during cigarette burning, and the ventilation for the unburned and burning cigarette. Three cigarettes with different circumference (super-slim 17 mm, 20 mm and king-size 24 mm) and with the same blend were compared.
The combustion coal and the unburned part of the cigarette were separated by a movable sealing tube. A soap film flow tube with low resistance was used to measure the ventilation air flow of the unburned part in real time and the total real time ventilation of the burning cigarette was obtained. The results were as follows: 1) Along with the burning, the total real time ventilation of the cigarette decreased gradually. 2) Compared with the first puff, the total real time ventilation of super-slim cigarettes in the last puff decreased 37.5 %. While for king-size cigarettes, the corresponding decrease is only 29.5 %. 3) Because of the resistance of combustion coal, same residual length of cut-tobacco segments showed great increases of real time ventilation in each puff for burning cigarettes compared to unburned cigarettes. Furthermore, the puff-by-puff average increase of burning super-slim cigarettes (74.5 %) is greater than that of king-size cigarettes (55.7 %) and 20 mm cigarettes (60.5 %).