The nexus of the indoor CO2 concentration and ventilation demands underlying CO2-based demand-controlled ventilation in commercial buildings: A critical review

The carbon dioxide (CO2)-based demand-controlled ventilation (DCV) has attracted prompt attention from the Heating, Ventilation, and Air-Conditioning (HVAC) industry since its very first invention. Since then, it has been penetrating from simple single-zone systems to complex system configurations in commercial buildings. While there has accumulated a large number of research on DCV applications, the most recent review paper on this topic was dated back to 2001 and inevitably missed a lot of recent revolutionary technologies. Therefore, to understand the opportunities and challenges associated with the CO2-based DCV, this study presents a timely review on the revolutions of the CO2-based DCV in commercial buildings, with a focus on the literature published in the last two decades. This paper is mainly centered on the trends and fundamental updates of the CO2-based DCV, with a particular focus on the nexus of the indoor CO2 concentration and ventilation "demands". First, the changes in building energy codes and standards related to the CO2-based DCV are reviewed. Second, the trends of paper distribution and the topic keywords are identified through the bibliographic analysis. Third, the fundamental updates regarding the indoor CO2 concentration are presented. The correlations between the CO2 and its influencing factors are discussed, and the CO2 concentration spatial distribution in different scenarios is summarized. Fourth, the role of CO2 in ventilation control is clarified. The correlation studies of the CO2 concentration and various ventilation "demands" are reviewed, and the impacts of the CO2-based DCV on indoor air quality are presented.