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Summary A novel concept is described here that utilizes externally applied heat to a solid rod of reconstituted tobacco biomass to form a stream of aerosol under progressively oxygen-deficient atmosphere. The boundary of auto-ignition was determined at oxygen concentrations of 0%, 5%, 10%, and 21% and then the effects of these different atmospheres on various parameters were studied. Experimental results indicated that the ignition temperature decreased with the increase of oxygen concentration and a negative temperature coefficient (NTC) for atmosphere with oxygen was observed at before but close to ignition temperature. Significant differences in the yields of CO and CO2 between oxygen and oxygen-free atmosphere were observed. The mass of aerosol produced under an inert atmosphere and reduced-oxygen atmosphere were characterized with selected volatile and semi-volatile components, phenols, aldehydes, and other organic compounds of interests. In addition, higher oxygen concentration resulted in higher bulk and surface oxygen content of solid-phase residue, the reduction of carbon and hydrogen element content and related functional groups, and the content of inorganic compounds also exhibited an increase with oxygen concentration. By systematically changing oxygen concentrations of the biomass bed with increasing temperatures, an aerosol stream of controlled chemical composition and yields could be formed without leading to ignition. Key chemical markers of inhalation harm were measured and compared to each other under different degrees close to combustion. Studying reconstituted tobacco or other biomass materials in such a way could provide alternative and useful information in the design heated biomass aerosol generators.

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.