Aerosol Formation and Transfer in Open- and Closed-Ended Heated Tobacco Products

Abstract

Summary A lit cigarette forms a positive and negative pressure zone by a puff with respect to the position of its paper burn line. Smoke aerosols generated from the two zones are then pulled through the rod under the puff to form the mainstream smoke. This phenomenon is fundamental to the thermophysics and the resultant chemical composition of the mainstream smoke. In this study, we created two different airflow pathways inside a heated tobacco rod by a puff, and investigated the differences in aerosol formation and its chemical compositions. The two different pressure-induced conditions, one through an open-ended tobacco rod (marked as HNB, a label of a designed airflow pathway of commercial heated tobacco products called heat-not-burn prior), and the other through a closed-ended tobacco rod (marked as NSC, a label of a novel-designed airflow pathway of heated tobacco products), were compared for their aerosol collected mass (ACM), the contents of nicotine, water and added aerosol agents such as propylene glycol (PG) and glycerol (VG), as well as selected aldehydes and ketones in the mainstream aerosol. Aerosol particle distribution and the heated temperature along different rod locations were also compared during a puff. The results indicated marked differences in the aerosol formation processes between the two HNB and NSC systems. The transfer ratios of the main aerosol components were significantly higher for the NSC; the levels of formaldehyde and acetaldehyde were significantly lower under the NSC than the HNB condition. There were also significant differences for the aerosol particle number concentration (APNC) and count median diameter (CMD) for the two systems. The lack of convective heat transfer in the aerosol formation under the NSC condition resulted in a relatively stable thermal aerosol generation zone, reflected by the temperature difference between the two systems in the selected locations. The NSC mode of tobacco heating thus offers a novel and enhanced aerosol generation for heat tobacco product designs.

A Comparative In Vitro Toxicological Screening of a Closed-End Heated Tobacco Product *

“…In short, the HTP-A airflow pathway (Figure 1A) was from the perforation on the hollow acetate tube because the tobacco end of the heating device was completely sealed. The HTP-B airflow pathway (Figure 1B) was from the tobacco end (8,9). The working mechanism behind the aerosol formation and transfer for the close-end HTP-A has been described before (8,9).…”

“…The air flow design of HTP-A and HTP-B is schematically shown in Figure 1 (8,9). In short, the HTP-A airflow pathway (Figure 1A) was from the perforation on the hollow acetate tube because the tobacco end of the heating device was completely sealed.…”

“…In this work, a novel HTP design that prevents the air flow from entering the tobacco end is described -this is called a closed-end HTP. The key design features and its working principle have been described before (8,9), more details will be given in the experimental section. In this work, we aimed to compare the aerosol chemistry, first using a limited number of toxicants measured on this close-ended HTP and a commercial HTP (IQOS TM ).…”

The Product Science of Electrically Heated Tobacco Products: An Updated Narrative Review of the Scientific Literature

“…Areas discussed include harmful and potentially harmful constituents (HPHCs), markers of combustion, toxicological risk exposure and health/cancer risk assessment, radioactivity, and nicotine stereochemistry. With respect to the articles identified that described chemical analyses of HTPs, articles or portions of their results were excluded from detailed discussion in this section of the review if they did not detail a direct quantitative comparison between the HTP(s) under investigation and other nicotine-or tobacco-containing products such as cigarettes and/or EVPs (i.e., quantitative data were reported solely for the HTP(s) investigated) [20][21][22][23][24]; only provided an analysis of chemical constituents present in consumables or only provided an analysis of emissions released by consumables using an experimental methodology which did not involve use of the consumable combined with the operation of the associated handheld device as intended by the manufacturer (i.e. creating an exposure scenario different from that of real-world product use) [25][26][27][28][29][30][31][32]; only provided an analysis of nicotine levels present in HTP aerosol and mainstream cigarette smoke without further detail [33].…”

Thermal De-Oxygenation to Form Condensable Aerosol From Reconstituted Tobacco without Auto-Ignition

“…In addition to pyrolysis temperature, oxygen, as one of the three major elements of combustion, is also decisive in controlling combustion. Based on the creation of a tobacco matrix low-oxygen pyrolysis environment and the establishing of a unique smoke extraction method, NSC has been constructed by B. LI et al (18) to ensure that the tobacco is heated rather than ignited, NSC is a label of the noveldesigned airflow pathway of heated tobacco products. Through the coordination of cigarettes and handheld devices, oxygen (or air) will not flow through the tobacco section during the main aerosol formation and transfer process, thus the aerosol generation mechanism for NSC is fundamentally different from the current heating tobacco products, especially the pyrolysis atmosphere and the airflow pathway.…”