PM2.5 and ultrafine particles in passenger car cabins in Sweden and northern China—the influence of filter age and pre-ionization

Abstract

The main aim of the study was to evaluate the influence of filter status (new and aged), pre-ionization, on the particle filtration in modern passenger cars. Measurements of in-cabin and outside PM 2.5 (dp < 2.5 μm) concentration and UFP (ultrafine particle, dp < 100 nm) counts, to calculate I/O (indoor to outdoor) ratios, were performed. They were done at two locations, to study the influence of different outside conditions on the HVAC (heating, ventilation, and airconditioning) system. The measurements were performed in two new cars, with similar HVAC systems and settings, using a new filter and an aged synthetic filter. Furthermore, an ionization unit was installed upstream of the filter in both cars. This enabled the study of filter status, with and without ionization, under common driving conditions. The results show that the HVAC system performances were very similar at the two locations, with average I/O ratios of 0.35-0.40 without ionization and 0.15-0.20 with ionization applied, although the outside conditions were considerably different. Furthermore, the aged filter clearly worsened the filtration ability. Considering the corresponding average PM 2.5 I/O ratios in one location as an example, the average for the new filter was 0.20 and 0.60 for the aged filter. The corresponding UFP I/O ratios were 0.24 and 0.57. Other findings are that the aged filter with ionization reached a performance close to the new filter (without ionization), and that increased ventilation airflow and decreased recirculation degree, as expected, led to an increase in the I/O ratio for both particle sizes.

Size-resolved simulation of particulate matters and CO2 concentration in passenger vehicle cabins

“…The vehicles being modelled in this study are the same as in a previous vehicle measurement study (Wei et al 2020 ), i.e. a Volvo XC90 (model year 2018) with an estimated cabin volume of 4.1 m 3 , and a Volvo S90 (model year 2018) with an estimated cabin volume of 2.9 m 3 .…”

“…On the other hand, the filtration process of particles is simulated with an ejection template at the filter component, where the ejection rate of particles is defined with the size-dependent filter efficiency η . This study simulated the same filters used in the validation measurements (Wei et al 2020 ), which are a newly manufactured filter and a 500-h-aged (end of service interval) filter of the same type. For the new filter status, the efficiency values were applied from several available supplier component tests.…”

“…The simultaneous in-cabin CO 2 concentration was logged as well in Sweden for all the test cases. More detailed descriptions can be found in the methods section of the previous paper by Wei et al ( 2020 ).…”

“…The cabin CO 2 concentration, an established indicator for air quality, is also modelled, considering that air recirculation might cause accumulated CO 2 (Kilic and Akyol 2012 ; Luangprasert et al 2017 ). The model is validated against previous vehicle measurements performed under various conditions (Wei et al 2020 ).…”

Vehicle cabin air quality: influence of air recirculation on energy use, particles, and CO2

“…The ventilation of the vehicle climate system also influences the concentration. Reduced airflow rate (Zhu et al 2007 ; Knibbs et al 2010 ; Abi-Esber and El-Fadel 2013 ; Jain 2017 ; Wei et al 2020 ) and the application of recirculation are beneficial in reducing the particles (Pui et al 2008 ; Qiu et al 2017 ).…”