PM2.5 and ultrafine particles in passenger car cabins in Sweden and northern China—the influence of filter age and pre-ionization
Journal article, 2020

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 PM2.5 (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 air-conditioning) system. The measurements were performed in two new cars, with similar HVAC systems and settings, using a new 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 PM2.5 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 of I/O ratio for both particle sizes.







vehicle cabin


Dixin Wei

Volvo Cars

Chalmers, Architecture and Civil Engineering, Building Services Engineering

Filip Nielsen

Volvo Cars

Lars Ekberg

Chalmers, Architecture and Civil Engineering, Building Services Engineering

Anders Löfvendahl

Volvo Cars

Maria Bernander

Volvo Cars

Jan-Olof Dalenbäck

Chalmers, Architecture and Civil Engineering, Building Services Engineering

Environmental Science and Pollution Research

0944-1344 (ISSN)

Vol. 27 24 30815-30830

Subject Categories

Mechanical Engineering

Environmental Engineering

Environmental Sciences

Driving Forces

Sustainable development

Areas of Advance




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