Providing a Controllable Lab Test Environment for Assessing the Performance of Vehicle Cabin Air Purification Systems by Determining the Air Quality Regarding PM2.5 and CO ₂

HVAC systems of passenger cars and especially their air purification performance gained prominence during the last years. One reason is the overall increased attention to air quality and its effect on human health. Recently, the WHO further tightened the recommended values for many pollutants. This will likely intensify the trend to more complex systems for improving the air purification functionalities. But, up to now there is no standard method for air purification performance testing. Existing standards cover the vehicle cabin air quality only regarding material emissions. Several studies address assessing the performance of air purification functionalities in most cases by real driving tests typically performed in urban areas. This approach results in proper values for the basic efficiency of single systems. But the level of pollutants in real environments differ considerably, which makes a comparison of different systems or varying application parameters at least complex. Hence, the aim of this study was to provide a controllable lab test environment for testing the whole vehicle with its HVAC system regarding its air purification performance. An atmosphere of KCl particles (focus on PM2.5) was chosen for representing the pollutant class of particulate matter. In addition, CO₂ was identified as an important pollutant, whose source is not the surrounding environment but the vehicle passengers. Literature reveals that the CO₂ concentrations within the vehicle cabin can reach critical concentrations, especially for air-recirculation mode and for a higher number of passengers. Hence, a system for dosing CO₂ was set up. It has five channels to simulate the CO₂ exhalation of up to five passengers. Its usability was tested by comparing the resulting CO₂ concentrations to an experiment with real passengers. At the end a feasible lab test environment was created. Furthermore, introduction of other pollutants (e.g., CO, O₃, NO_x, biological matter) is also possible.