According to a previous study [3], there is a relationship between change of odor characteristics and that of evaporator surface condensed and vaporized (when the compressor is turned on and off). Furthermore, many consumer complaints were induced when drivers turn on and off their air-conditioning system as well. Therefore, air-conditioning operation was monitored with the change of temperature and relative humidity, and the odor was evaluated by the trained panelists to find the relationships between them. There were significant changes in odor characteristics during the evaporator operation (Fig. 6).