(179i) Factors Affecting CO2 Accumulation in the Motor Vehicle Cabin

Unmitigated carbon dioxide (CO₂) accumulation within vehicle cabins may pose risks to drivers due to cognitive impairment caused by high CO₂ concentrations, e.g. exceeding 1,000 ppm for several minutes of exposure. This work investigates the effects of air recirculation mode and vehicle speed on CO₂ buildup profiles within a mid-size sedan vehicle (most popular category of cars sold in the United States). The CO₂ concentration was measured continuously with a double beam-based infrared pre-calibrated monitor with 10 s resolution inside a vehicle driven at different speeds over periods of up to 50 min. The use of recirculation mode resulted in the accumulation of CO₂ to levels above 1000 ppm in less than 10 minutes. Vehicle speed was shown to have a moderating effect on CO₂ buildup, which was correlated with increased effective air exchange between the vehicle cabin and the surrounding environment. A CO₂ management strategy was evaluated to mitigate the vehicle occupants’ exposure to high CO₂ levels resulting from the use of recirculation mode. This strategy aimed to maintain CO₂ concentrations at a safe level within the vehicle cabin by turning on and off the recirculation mode, which enabled the control of indoor air quality within the vehicle cabin. The driver’s energy expenditure (in kcal/day) was estimated from the experimentally determined CO₂ generation rates. A box model was used to simulate CO₂ concentration profiles when multiple occupants were present in the vehicle, and to predict the effects of vehicle speed, effective air exchange rate and driver’s energy expenditure in different scenarios, providing broader insights on the potential risks associated withCO₂ level accumulation within vehicles.