Effects of ventilation rate and e-liquid composition on aerosol release characteristics of a novel hybrid tobacco product

This study investigates the aerosol particle number concentration (PNC) and size distribution generated by electronic cigarettes (EC), heated tobacco products (HTP), and a novel composite system combining both. Aerosol characteristics were measured using a DMS500 fast particle spectrometer. The results indicate that ventilation rate and e-liquid ratio significantly affect the generation of aerosols, and exhibit different patterns under different smoking modes. In EC-only use, increased ventilation reduced the aerosol collected mass (ACM) and PNC while increasing the count median diameter (CMD). Conversely, for both HTP-only and composite smoking, PNC exhibited a non-monotonic relationship with ventilation, peaking at a 50% rate due to altered flow dynamics and supersaturation levels affecting aerosol formation. The composite mode uniquely decoupled the ACM trend from PNC due to supplementary aerosol from the EC. Furthermore, while a higher propylene glycol ratio elevated PNC and CMD in EC-only smoking, its effect was weakened in the composite smoking mode. This attenuation is attributed to complex adsorption-release processes and the coupling of EC vapor with tobacco volatiles within the tobacco section. These findings elucidate the intricate formation mechanisms of smoke aerosols in composite systems, providing critical insights for exposure risk assessment and the development of reduced-harm products.