Reports that as part of a long-term study of ventilation and indoor air quality in new office buildings, an environmental performance evaluation was conducted in a new office building in Overland, Missouri. Ventilation rates and carbon dioxide levels were monitored for two years. In this effort, automated tracer gas and CO2monitoring systems were employed to measure whole-building air change rates and CO2concentrations. Presents the measurement results. Discusses 1) the relationship between the building air change rate and indoor/outdoor temperature difference, 2) the average and maximum CO2concentrations in the HVAC return ducts and occupied spaces and 3) the relationship between the maximum daily CO2concentration and building air change rate.KEYWORDS: Offices, USA, case studies, carbon dioxide, ventilation, air change rate, measuring, monitoring, automatic, new buildings, tracers, indoor, outdoor, temperature difference, sulphur hexafluoride