Early post-emission particle decay dynamics of E-cigarette aerosols under controlled conditions

Thirdhand smoke consists of residual pollutants that remain on indoor surfaces after smoking or vaping and may contribute to later exposure through desorption and gas-particle-surface partitioning. However, the early post-emission aerosol dynamics that precede and may contribute to residue formation remain poorly characterized for electronic cigarettes. Here, we quantify particle-number decay following a single controlled electronic-cigarette puff in a controlled small-volume chamber under defined airflow and surface conditions. Particle concentrations showed a consistent two-stage decay pattern: a shorter initial decline, potentially driven by airborne removal and surface deposition, followed by a long-tail post-emission particle-decay phase potentially influenced by surface-related and gas-particle processes. Across triplicate experiments, the tested surface configurations produced no consistent change in the fitted decay parameters, whereas increased airflow accelerated particle clearance. These results characterize the early post-emission behavior of electronic-cigarette aerosols and establish a quantitative baseline for processes that may contribute to subsequent thirdhand residue formation.