In a highly airtight house, it is well known that air pollutants remain if periodic ventilation is not performed. The use of deodorizers and air cleaners is increasing now, as residents are showing a greater interest in eliminating offensive household odors. We conducted a questionnaire survey about the detection of household odors and conducted ventilation experiments with residents in the Hokuriku and Kansai areas. More than 80% of the respondents detected odors in the living room, with 30% indicating that they were unpleasant. The most common odors detected in the living room, as indicated by 50% of the respondents, were cooking odors. The smell of mold, garbage, and cigarette smoke were rated as less intense than cooking smells, but were still regarded as being strong and unpleasant by residents. The degree of intensity of odors detected in the living room depends on the distance between the living room and the source of the odors. Opening windows was the most effective way of eliminating odors, followed by turning on the ventilation fan. Cleaning the range hood frequently was also found to be an effective way of preventing the diffusion and penetration of odors.