Influences of Airflow Pathway and Velocity on Aerosol Release Mechanisms in Granule-Based HTP

Summary To investigate the effect of the airflow velocity on the mechanism through which aerosol is released in granule-based heated tobacco products (HTPs), experiments were conducted using two airflow pathways: open-ended and closed-ended configurations. The patterns of release of aerosol collected mass (ACM) and key aerosol components (nicotine, water, glycerol, and propylene glycol) and the distribution patterns of nicotine, glycerol, and propylene glycol in smoked cigarettes were measured. The results indicated that for the open-ended pathway, the airflow velocity did not strongly affect the total release amounts of ACM and its key components. The distribution of each component in the cigarette after it was smoked was also found to be relatively unaffected by the airflow velocity. However, for the closed-ended pathway, as the airflow velocity was decreased, the ACM and its total release amount decreased, and the residual amounts of each component in the tobacco granules and filter rod increased. In addition, the puff-by-puff release patterns of aerosols and their key components were different for the two airflow pathways. Specifically, for both pathways, the puff-by-puff ACM and water release gradually decreased after peaking quickly, whereas the levels of glycerol gradually increased, peaking at 7 or 8 puffs. The amounts of propylene glycol and nicotine first increased and then decreased for the open-ended pathway, reaching a peak at 4 or 5 puffs, whereas for the closed-ended pathway, these amounts gradually increased and peaked at 7 or 8 puffs. The aerosol particle size distribution results revealed that due to different processes of aerosol condensation and nucleation, as the airflow velocity was decreased, the aerosol number concentration and volume concentration decreased for both pathways but the median particle size increased. The closed-ended pathway resulted in a greater decrease or increase than did the open-ended pathway.