Indoor carbon dioxide – Ventilation, indoor air quality and human health

Indoor carbon dioxide (CO 2 ) concentrations have been discussed for centuries in the context of indoor air quality (IAQ) and ventilation. Over the past century, measurement and simulation of indoor CO 2 levels have been applied in many studies of IAQ, ventilation and human health, comfort and productivity. Such studies became more prevalent in the 1980s as IAQ became recognized as an important public health concern, and consideration of CO 2 became even more frequent in response to the COVID-19 pandemic. We launched this special issue to showcase recent scientific advancements in CO 2 monitoring, simulation and interpretation. This special issue was motivated by the rapid growth of CO 2 -related research and application during and after the COVID-19 pandemic, when CO 2 concentrations were widely promoted as indicators of ventilation, infection risk, and IAQ. While this trend has raised awareness of IAQ and ventilation, it has also highlighted the need for more rigorous application and interpretation of indoor CO 2 , as well as more innovative approaches. Although some authors were invited to contribute based on their leadership in the field, the call for papers was broadly open to the international community. In fact, most of the authors published herein were not directly involved in pandemic-response committees or prior workshops, ensuring that this issue better represents the broader research community. This special issue has collected seven cutting-edge and rigorously reviewed articles, all of which are open access, covering a spectrum of impactful research topics from lab-scale experiments, single-building tests to large-scale city-wide field measurement campaigns, and from human’s cognition tests, numerical simulations of building systems to field investigations during and after the COVID-19 pandemic