ASHRAE Position Document on Indoor CO2

Indoor CO₂ concentrations are often discussed in the context of ventilation and indoor air quality (IAQ), including indoor CO₂ as an IAQ metric, ventilation rate estimation using CO₂ as a tracer gas, control of outdoor air ventilation and impacts of CO₂ on building occupants. More recently CO₂ has been discussed in the context of airborne infectious disease transmission. However, many applications of indoor CO₂ do not reflect a sound technical understanding of the relationship between indoor CO₂ concentrations, ventilation and IAQ, and some applications have actually been technically flawed. In response to these concerns, ASHRAE has recently issued a Position Document on the role of indoor CO₂ in the context of building ventilation and IAQ. This column presents the positions and recommendations in the document, which also contains a thorough discussion of the supporting background and extensive references for the interested reader.