CO2 concentrations in traditional ventilation systems often exceed 1 000 ppm, especially in crowded rooms with poor ventilation. Indoor levels can – with sub-optimal ventilation systems – reach several thousand parts per million. For example, the concentration of CO2 in some classrooms has been reported to occasionally exceed 3,000 ppm.
Numerous clinical studies show human performance and decision-making is impaired as early as at an indoor CO2-level of 1 000 ppm. For example, both The Natural Institute of Environmental Health Sciences and Environmental Health Perspectives has published these kind of studies (in October 2015 and December 2012, respectively).
Five common test areas of these two studies (Basic Activity Level, Applied Activity Level, Information Usage, Breadth of Approach and Strategy) shows very similar results.
In average the results in these test areas decreased with almost 20 % when CO2 levels increase from 600 to 1 000 ppm. At 1 400 ppm, the average decrease is 50 % and at 2 500 ppm it is 65 %.
According to these studies, it is obvious that human mental performance is gravely degraded if the indoor CO2-level exceed 1 000 ppm. For most companies the performance of their employees is vital for making profit and therefore this proven decrease in performance levels must be economically important.
With continuous measurements and ventilation adjustments the indoor CO2-level can be kept low to maintain optimal productivity while at the same time keep the energy costs as low as possible.