Measurement of Carbon Dioxide in Vehicle Cabin to Monitor IAQ during Winter Season with HVAC Unit Operating In OSA Mode

Field tests were conducted on a MY 2003 vehicle with the HVAC unit in OSA mode to monitor build-up of the CO₂ concentration inside the cabin as a function of number of occupants, vehicle speed and ambient temperatures. These tests were conducted in the winter season by driving the vehicle in Detroit Metro area in city (Farmington Hills) and highway traffic conditions. Based on this investigation it is determined that the measured cabin concentration levels reaches ASHRAE (Standard 62-1999) specified magnitudes with four occupants in the vehicle. For this investigation, one to three occupants inside the cabin did not increase the level of cabin carbon dioxide to the levels specified by ASHRAE standard. A maximum concentration with four occupants was measured at 1700 ppm. The cabin concentration level would be higher for vehicles that have lower body leakages compared to this one. Body leakage rate is one of the several factors that affects the build-up of CO₂ concentration within the cabin. Details of the investigation are presented in this paper.