The Air Quality Paradigm inside Car Microenvironments; Balancing between PM2.5 and CO2 Offsets

Abstract

In confined spaces, such as vehicle cabins, air quality can easily improve or deteriorate as it can be considered as a semi-controlled environment. By controlling the indoor-outdoor exchange rate using the vehicle's ventilation system or by opening or closing of windows, car drivers have the ability to control their exposure to both indoor and outdoor pollutants. Besides the adverse health effects of outdoor air pollution, increasing health evidence reports on impaired cognitive functioning due to elevated CO2 exposure in indoor environments, impacting i.e. alertness, exhaustion and decision making. Impairment of these cognitive functions is typically associated with a higher prevalence of road accidents. This short paper reports on in-vehicle sensor measurements evaluating the occupant exposure to both outdoor particulate matter (PM10, PM2.5) and indoor CO2, under varying car occupancy and ventilation settings. Measurements demonstrate the varying contribution from indoor and outdoor pollution under different ventilation settings and car occupancies and confirm elevated CO2 concentrations (up to 2000 ppm), recently documented to impact cognitive performance. Activating internal recirculation for 15 minutes resulted in median concentration decreases of 44-59% and 53-64% for PM2.5 and PM10 respectively, while the CO2 concentration simultaneously increased by 23-39% and 244%, depending on the car occupancy (1 vs 5 occupants). This exploratory study shows that low-cost air quality sensors are able to capture in-vehicle dynamics. Automotive integration of onboard air quality sensors with automatic ventilation controlling in-vehicle exposure levels adds value, especially considering the increasing evidence of impact of CO2 on impaired cognitive functioning.