Quantitative Analysis of the Parameters Affecting In-Cabin to On-Roadway (I/O) Ultrafine Particle Concentration Ratios

Abstract

A mass-balance indoor particle dynamic model was adopted and modified to investigate how on-roadway ultrafine particle (UFP, diameter < 100 nm) concentrations and vehicle ventilation settings affect UFP levels inside vehicles. The model was first parameterized focusing on a mechanistic, simulation-based interpretation of in-cabin data reported in Zhu et al. Under condition (3), the effects of penetration factor, deposition coefficient, and vehicle speed were comparable. The modeled I/O ratio was inversely proportional to the airflow rate from mechanical ventilation in the whole range (0-360 m 3 h −1 ) with 10-20% influence depending on the particle size.

Influences of Commuting Mode, Air Conditioning Mode and Meteorological Parameters on Fine Particle (PM2.5) Exposure Levels in Traffic Microenvironments

“…The lower O/I ratio was also due to less advanced automobile manufacturing, ventilation technology and filtration system (Xu and Zhu, 2009;Knibbs et al, 2010). However, most of the ratios in this study were found to be higher than 1, which was similar to the results from studies after 2005 (Table 2).…”

Ultrafine particle infiltration into passenger vehicles. Part II: Model analysis

“…For example, a previous study assumed that infiltration is negligible (Pui et al, 2008). Xu and Zhu (2009) improved the approach of Pui et al (2008) by introducing a quantitative relationship, which eliminates the need to assume negligible infiltration and quantified infiltration using an idealized leakage model (Baker et al, 1987). However, the leakage model of Baker et al (1987) only works for idealized conditions and requires measurements of complex leakage geometry.…”

Analysis of PM2.5 distribution and transfer characteristics in a car cabin

“…Lee et al also pointed out that 10-50% of the exposure to ultrafine particle in the car microenvironment occurs during commuting time of one hour a day [18]. Xu and Zhu analyzed the impact of ultrafine particles' inside-to-outside PM2.5 concentration (I/O ratio) factors using mass balance modeling [19]. Meanwhile, Hudda quantitative research on the factors influencing the concentration of PM2.5 in car cabins is very limited.…”