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40th AIVC - 8th TightVent & 6th venticool Conference, 2019 Residential Application of an Indoor Carbon Dioxide Metric



Andrew K. Persily, Brian J. Polidoro


Indoor carbon dioxide (CO2) concentrations have been used for decades to evaluate indoor air quality (IAQ) and ventilation. However, many of these applications have reflected a lack of understanding of the connection between indoor CO2, ventilation rates and IAQ. In particular, a concentration of 1800 mg/m3 (1000 ppmv) has been used as a metric of IAQ and ventilation, without considering its basis or significance. After many years of trying to dissuade practitioners and researchers from using CO2 as a metric of ventilation and IAQ, the author has developed an approach to determine CO2 levels that can be used as more meaningful indicators. This approach is based on the fact that space types differ in their internal contaminant sources, recommended or required ventilation rates, occupancy and other important features that impact indoor CO2 concentrations. Rather than employ a single CO2 concentration for all spaces and situations, this alternative approach involves the estimation of space-specific CO2 concentrations. The concept considers the steady-state CO2 concentration that would be expected in a given space type based on its intended or expected ventilation rate per person, the time to achieve steady-state, the number of occupants as well as the rate at which they generate CO2, and the occupancy schedule as it impacts whether or not steady-state is likely to be achieved. This alternative approach was described in a previous AIVC conference paper, with sample calculations presented for several commercial and institutional building spaces. Those calculations yielded potential CO2 concentration metrics, along with measurement times after full occupancy. Based on these analyses, it was stressed that reported CO2 concentrations for comparison to these or other metrics need to be associated with a measurement time relative to the start of occupancy as well as additional information about the space in question and its occupancy. Since this previous work, an online cal
Proceedings Title
Conference 40th AIVC – 8th Tight Vent & 6” venticool Conference in Ghent Belgium
Conference Dates
October 15-16, 2019
Conference Location
Ghent , -1


Building performance, carbon dioxide, indoor air quality, metrics, residential, ventilation
Created October 24, 2019