Bimodal particle size distribution and aging kinetics of heated tobacco product aerosol

In order to investigate the aging characteristics of aerosols released from heated tobacco products and the influences of puffing parameters (interval, puffing volume and heating duration) on the aging kinetics, aerosol measurements were conducted with a smoking machine and an electrical low-pressure impactor. The aerosol growth characteristics were studied via a"vapor-glycerol"binary aerosol kinetic model. The results showed that: 1) The aged aerosol from heated tobacco products presented a bimodal particle size distribution with the total concentration of aged aerosol number ranging from 1.3 × 10⁹ to 1.7 × 10⁹ per cm³, and the average aerosol particle size between 0.15-0.25 μm. 2) Puffing volume influenced the bimodal particle size distribution more significantly; the larger the puffing volume was, the less significant the first peak in the bimodal particle size distribution turned out to be. The influences of puffing interval and heating duration on the bimodal distribution were relatively minor. Puffing interval, puffing volume and heating duration had less effects on the average particle size. 3)The particle size distribution of the "vapor-glycerol" binary aerosol was bimodal according to theoretical calculations, and the particle size distribution significantly shifted to larger particle sizes with the increase of aging time. However, the increase of glycerol concentration calculated to have insignificant effect on the second peak, which was consistent with the experimental results.