A new study from the Department of Energy’s Lawrence Berkeley National Laboratory and the State University of New York, published in Environmental Health Perspectives, claims that “moderately high indoor concentrations of carbon dioxide (CO2) can significantly impair people’s decision-making performance.” This was a very small study consisting of just 22 college students ( 24 originally) who were divided into 6 groups, each of which stayed in a closed room for 2.5-hour stretches at various carbon dioxide concentrations for one day.
Results: “On nine scales of decision-making performance, test subjects showed significant reductions on six of the scales at CO2 levels of 1,000 parts per million (ppm) and large reductions on seven of the scales at 2,500 ppm.” However, while “most decision-making variables showed a decline with higher concentrations of CO2, …measures of focused activity improved.” The researchers also note “The strength of the effects at 2,500 ppm CO2 is so large for some metrics as to almost defy credibility, although it is possible that such effects occur without recognition in daily life.” (See Berkeley press release here and EHP press release here, Full EHP report here. )
There are some possible confounding factors which could effect the test results, but which the researchers did not discuss. Since each group went through three sessions in one day, results may partially depend on the order of concentrations used and the time of day. For instance, the subjects may be more fatigued during the last test of the day or may be drowsy just after lunch. There apparently was no control group. Each group was tested just once so there was no effort to see if group results were repeatable.
The Berkeley researchers note: “While the results need to be replicated in a larger study, they point to possible economic consequences of pursuing energy efficient buildings without regard to occupants.”
U.S. Navy submariners and astronauts would disagree with the results of this study. There has been abundant research on the physical and mental effects of carbon dioxide in enclosed spaces (see report from The National Academies Press here):
“Data collected on nine nuclear-powered ballistic missile submarines indicate an average CO2 concentration of 3,500 ppm with a range of 0-10,600 ppm, and data collected on 10 nuclear-powered attack submarines indicate an average CO2 concentration of 4,100 ppm with a range of 300-11,300 ppm.”
“A number of studies suggest that CO2 exposures in the range of 15,000-40,000 ppm do not impair neurobehavioral performance.”
“CO2 at 40,000 ppm for 2 weeks did not affect performance on multiple tests of cognitive function in physically fit young airmen…”
“Exposures at 50,000-67,500 ppm in 19.2% oxygen for 37 h caused decreased hand-arm steadiness but caused no changes in computing, translating, number checking, or discrimination of pitch or loudness…”
Why did Berkeley/SUNY conduct this research? Perhaps the EHP headline offers a clue: “Is CO2 an Indoor Pollutant? Direct Effects of Low-to-Moderate CO2 Concentrations on Human Decision-Making Performance.” This ties in with the EPA’s contention that carbon dioxide is a “pollutant” that must be regulated. The study was funded by the EPA through several sub-agencies.