Monitoring of carbon dioxide (CO2) accumulation in vehicle cabin

The number of registered vehicles worldwide is increasing dynamically in recent years, over 72 million automobiles were sold in 2015. The AAA Foundation for traffic safety found that driver or passengers spending an average of 46 minutes per day inside a vehicle. Unfortunately, human awareness of indoor air quality in the vehicle cabin is surprisingly low. The quality of air within the vehicle cabin can influence the occupants' comfort level. One of the main indicators of enclosed environment's air quality is the carbon dioxide (CO
2
) content which is released through human breathing. High level of CO
2
can cause the occupants feel fatigue, drowsiness and slow reaction of actions. Many published works show that air conditioning (AC) with recirculation mode inside a vehicle could minimize the particulate pollutant flow into the cabin. However, it does not reduce the amount of accumulated CO
2
. The purpose of this paper is to study the concentration of the accumulated CO
2
under different vehicle speed and number of occupants under AC recirculation mode by applying qualitative data collection method. Then, the cooling period of cabin temperature after vehicle parked under blazing sun. Experimental results show that accumulated CO
2
concentration exceeded the recommended threshold value of 1200 ppm after 10 minutes when two passengers occupied the vehicle's cabin. The CO
2
concentration exceeded the threshold 3.33 times faster for two occupants compare to one occupant in the cabin with the same speed. Vehicles moving at higher speed of 90km/h shows a lower accumulated concentration of CO
2
when compared with lower vehicle speed. Vehicle speed of 50 km/h had recorded the shortest time taken with 9 minutes to pass 1200 ppm. Then, a car which parked under a 36.5 °C on a sunny day for 3 hours will reach the cabin temperature of 49.5 °C.