The concentration of carbon dioxide in office building was used to monitor indoor air quality. A total of one hundred and one (111) measurements was carried out in five buildings during the last three years. The number of measurements was grouped into five concentration ranges of carbon dioxide. This concentration distributions were then related to the building occupant's complaints and the amount of fresh make‐up air from outdoor. Higher carbon dioxide concentration was demonstrated as an indicator of poor air quality in the office building. This technique appeared to be sufficiently sensitive and could provide building managers a timely and inexpensive tool for office building ventilation surveillance.