Behavior of carbon monoxide, nitrogen oxides, and ozone in a vehicle cabin with a passenger

Drivers and passengers are exposed to high concentrations of air pollutants while driving. While there are many studies to assess exposure to air pollutants penetrating into a vehicle cabin, little is known about how individual gas pollutants are behaving (e.g. accumulating, depositing, reacting etc.) in the cabin. This study investigated the characteristic behavior of CO, NO, NO2 and O3 in a vehicle cabin in the presence of a driver with static, pseudo dynamic and dynamic tests. We found in our experiments that CO and NO concentrations increased while O3 and NO2 concentrations decreased rapidly when cabin air was recirculated. A kinetic model, which contains 20 chemical reactions, could predict the static test results well. CO and NO accumulations in the cabin were due to exhalation from the driver and conversion of NO2 to NO upon deposition to surfaces may also play a role. Pseudo dynamic and dynamic test results showed similar results. During the fresh air mode CO, NO, and NO2 followed similar trends between the inside and outside of the cabin, while in cabin O3 concentrations were lower compared to outside concentrations due to reactions with the human and surface deposition. The Cabin Air Quality Index approached 0.8 and 0.4 for O3 during pseudo dynamic and dynamic tests, respectively. Accumulation of NO in the cabin was not obvious during the dynamic test due to a large variation of outside NO concentrations. We encourage auto manufacturers to develop control algorithms and devices to reduce a passenger's exposure to gaseous pollutants in vehicle cabins.