Cigarette Smoke Formation Studies: IV. The Dynamic Measurement of the AxiaI Density of a Burning Cigarette

Much research has gone into establishing the temperature gradients that exist inside a burning cigarette. These temperature gradients should correspond to changes in the density of the tobacco column due to the condensation and subsequent re-evaporation of volatiles resulting from pyrolysis, combustion, and final ash formation. These dynamic measurements on the burning cigarette were made using a modified beta thickness gauge. A beam of collimated beta particles from a ³²P-source is projected through the side of a cigarette at a fixed position. The cigarette is allowed to burn past the focused beta beam. The number of transmitted particles is dependent upon the density of the mass penetrated by the incident particles, and is reflected as a change in the number of counts detected per unit time. A density profile of the burning cigarette has been established for both the puffing and static modes. These density changes are correlated with published temperature profiles. The buildup of the volatile materials (mostly water) on the tobacco rod behind the pyrolytic region is presented. The rate of evaporative losses of these condensables is shown to be dependent on puff count (cigarette length). A detailed density profile of the condensing materials from a single puff has been established. The relationships of these density changes to current smoke formation theories are discussed