Impact of Ventilation Modes on PM _2.5 Concentrations in Electric Passenger Cars: An Analysis of In‐Vehicle and Out‐Vehicle Air Quality

The in‐vehicle microenvironment has become a crucial setting for traffic‐related PM 2.5 exposure due to the continuous increase in vehicle numbers and the cumulative time spent inside vehicles. This study investigates the impact of different ventilation modes on PM 2.5 concentrations in newly manufactured, off‐road electric passenger cars. Real‐time PM 2.5 concentration data inside and outside the cars were collected using a particle monitor. The analysis focused on PM 2.5 concentration characteristics, the indoor‐to‐outdoor PM 2.5 concentration ratio (I/O ratio), reduction efficiency, and infiltration factor. The results indicated that ventilation modes significantly affect in‐vehicle PM 2.5 concentrations ( p < 0.05), with concentrations ordered as follows: outside air ventilation (OA) > no air ventilation (NONE) > in‐vehicle recirculation (RC). The correlation between in‐vehicle and out‐vehicle PM 2.5 was highest in the OA mode. Median I/O ratios for NONE, RC, and OA modes were 0.008–0.020, 0.003–0.008, and 0.011–0.109, respectively, decreasing and stabilizing over time, with greater fluctuations in the OA mode. Reduction efficiency increased over time, inversely related to the I/O ratio, with the RC mode showing the highest efficiency, 1.06 times that of the OA mode. Infiltration factors were highest in the OA mode (0.0139–0.1043), followed by NONE (0.0077–0.0254), and RC (0.0034–0.0077). In all ventilation modes, the contribution of out‐vehicle PM 2.5 to in‐vehicle concentration exceeded 95%, with the OA mode’s average contribution being 12.70 and 3.73 times that of RC and NONE modes, respectively. Temperature and humidity significantly influenced in‐vehicle PM 2.5 concentration and the I/O ratio ( p < 0.05). The study demonstrates that vehicle ventilation modes significantly affect in‐vehicle PM 2.5 concentration and infiltration characteristics. Increased air exchange enhances the impact and correlation of out‐vehicle PM 2.5 on in‐vehicle concentrations. Optimizing ventilation mode selection can effectively reduce in‐vehicle PM 2.5 exposure, particularly by prioritizing recirculation mode when external pollution levels are high.