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A fractional recirculation of cabin air was proposed and studied to improve cabin air quality by reducing cabin particle concentrations. Vehicle tests were run with differing number of passengers (1, 2, 3, and 4), four fan speed settings and at 20, 40, and 70 mph. A manual control was installed for the recirculation flap door so different ratios of fresh air to recirculated air could be used. Full recirculation is the most efficient setting in terms of thermal management and particle concentration reduction, but this causes elevated CO₂ levels in the cabin. The study demonstrated cabin CO₂ concentrations could be controlled below a target level of 2000 ppm at various driving conditions and fan speeds with more than 85% of recirculation. The proposed fractional air recirculation method is a simple yet innovative way of improving cabin air quality. Some energy saving is also expected, especially with the air conditioning system.

People are exposed to disproportionately high concentrations of air pollutants daily on and near the road during their ride, walk, and residency. Currently air quality monitoring is performed mostly at background locations far away from the road and distinctive point, line, and area emission sources, failing to report concentrations on the road. This study presents an innovative air quality monitoring method using a network of vehicles equipped with air quality sensors (AQSs). Vehicles are connected to internet through either cell link or apps used by drivers. A cloud server collects the data and updates air quality concentration maps every 10 minutes. The study presents very high temporal and spatial resolution maps at a fraction of the cost of previous studies.

More than a hundred million Air Quality Sensors (AQS) have been used since the late 80s to improve in-cabin air quality on high-end cars. This is more than a billion dollars spent. A study conducted in two major cities (USA & Europe) showed that a novel method based on high-resolution air quality maps outperforms the use of on-board AQS. The total passenger exposure to pollution was compared for several flap management algorithm cases: flap always open, random open/close, map-based algorithm, and AQS-based algorithm. The results are likely to disrupt the AQS market since the map-based method is a pure software solution with lower cost per vehicle than the sensor itself. The data volume used to calculate the air quality maps was sufficient to obtain good average correlations between individual trip pollution profiles and the map Air Quality Indices (AQI) along the trip path.