Dilution of mainstream tobacco smoke and its effects upon the evaporation and diffusion of nicotine

The proportion of nicotine in the vapour phase of different dilutions of mainstream tobacco smoke has been investigated. The percentages of the total available nicotine initially in the vapour phase were (0.5 ± 0.3)% and (0.7 ± 0.4)% when the averaged initial particle number concentrations were (3.8 ± 0.6) × 107 and (1.2 ± 0.1) × 109 particles per cm3, respectively. The maximum percentages of the total nicotine that entered the vapour phase via evaporation from the particles decreased from (21 ± 5)% to (4 ± 3)% at the above respective concentrations. Results implied that there is a tendency towards equilibrium and that further dilution is required to re-establish evaporation. Further experiments, in which a 35 cm3 puff of mainstream tobacco smoke was drawn from a chamber, found that the amount of nicotine evaporating from the particles increased linearly as the initial particle number concentration of each puff increased. However, as the initial concentration approached (2 ± 1) × 107 particles per cm3, further increases were found to have a limited affect upon the amount of nicotine evaporating from the mainstream tobacco smoke particles.