In recent years, the focus on air quality and its impact on human health has become increasingly prominent. Efficient filtration for vehicle cabins (Cabin Air Filters) is considered as more and more important.

A Smart Cabin Air Filter System has been developed to provide drivers with the best possible protection from pollutants in the car cabin. This system includes up to three different filtration stages: a pre-filter, a HEPA filter and optionally a state-of-the-art cabin air filter in the air conditioning system. Additionally, the system is equipped with particle sensors to measure PM2.5 concentration inside the vehicle and in the ambient air, as well as CO₂ sensors to monitor the CO₂ levels inside the car. These sensors control the proportion of fresh air and the operation of the HEPA filter to achieve the best air quality in the cabin while optimizing energy consumption.

The development of suitable filtration materials for this purpose should not only be based on laboratory tests according to DIN 71 460. Additional field tests are essential to achieve optimum results for the development of efficient particle filtration. Thus, an electric demo car was equipped with such a system to prove its functionality and effectiveness in the field.

Proof-of-concept studies in vehicle air conditioning, especially for comparative tests of suitable filter materials, are strongly dependent on a stable size distribution of the ambient air aerosol in order to ensure comparable conditions for the tests. However, the ambient conditions in road traffic are highly variable, even on the same route and stable weather conditions, which significantly limits comparability.

To build a bridge between standardized laboratory tests with monodisperse aerosol according to DIN 71 460 on filter elements and tests in the air conditioning system or filtration unit of a vehicle in the field, tests with the Smart Cabin Air Filter System were carried out in the vehicle in a climatic chamber. These stationary tests were conducted with simultaneous measurements of PM2.5 and ultrafine particle concentrations.

For this purpose, an artificial aerosol with a similar size distribution compared to the ambient aerosol was generated. Many years of experience from field tests in various driving situations formed the basis for this artificially generated aerosol with a mixture of sodium chloride (NaCl, many very small particles, but hardly any particle mass) and ISO fine dust A2 (high number of larger particles, high particle mass PM2.5 / PM10). The aerosol was supplied into the test chamber ....