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 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 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 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 in the I/O ratio for both particle sizes.
Highlights
During the last 50 years, we have seen an increased population with increased living standards, followed by an increased number of plants for electricity generation and an evergrowing demand for transports, to a large extent based on fossil fuels
The results are based on PM2.5 concentrations and UFP counts (10– 100 nm), both inside and outside the car, as well as I/O ratios, in order to facilitate comparisons with results from other studies
Results for different locations, baseline and with ionization, filter status, different airflows and recirculation degrees are shown in diagrams in the following sub-chapters
Summary
During the last 50 years, we have seen an increased population with increased living standards, followed by an increased number of plants for electricity generation and an evergrowing demand for transports, to a large extent based on fossil fuels This has led to air quality problems, especially increased number of airborne particulate matter. UFPs (ultrafine particles, which have aerodynamic diameter less than 100 nm) can more deposit in the lung alveoli (Mitsakou et al 2007), cause greater inflammatory response and move to other organs (Oberdörster 2000). Vehicle passengers are challenged with pollutants from dense surrounding traffic, where elevated particle concentration could exist (Ramos et al 2016), and attributable to UFPs from traffic exposure potentially damage lung function (McCreanor et al 2007)
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