Evaluating building IAQ and ventilation with indoor carbon dioxide.

A number of approaches exist to evaluate building ventilation and indoor air quality. In some situations, the measurement and analysis of indoor carbon dioxide concentrations can be useful for understanding indoor air quality and ventilation. On the other hand, oversimplified descriptions of measurement procedures based on carbon dioxide have been presented, and there have been many instances in which indoor carbon dioxide concentration measurements have been misinterpreted and misunderstood. This paper describes various applications of carbon dioxide concentrations for evaluating building air quality and ventilation and the factors that need to be considered in their use. While carbon dioxide concentrations do not provide a comprehensive indication of indoor air quality, they can be used to indicate the acceptability of a space in terms of human body odor. Also, under some circumstances carbon dioxide can also be used to estimate building air change rates and percent outdoor air intake at an air handler. These uses of indoor carbon dioxide concentrations, and the situations in which their use is appropriate, are described. In addition, the factors that must be considered when using indoor carbon dioxide concentrations in these ways are also described. These factors include building and ventilation system configuration, occupancy patterns. Non occupant carbon dioxide sources, time and location of air sampling, and instrumentation for concentration measurement.