Being Indoors Can Impair Mental Performance

“One touch of nature makes the whole world kin.” —William Shakespeare, Troilus and Cressida

In A Nutshell

It’s been known for decades that very high concentrations of carbon dioxide can have a detrimental effect on people. Scientists believed these effects started when the concentration of CO2 in the air was around 10,000 parts per million. New research has shown that mental performance is reduced at normal indoor levels, up to 2,500 ppm. Scientists tested people at these levels and compared them to people working at high-end outdoor levels of 600 ppm. Those at the indoor levels performed worse on all measures and were comparatively dysfunctional in strategic thinking and taking initiative.

The Whole Bushel

Researchers at the famous Lawrence Berkeley National Laboratory, run by the the United States Department of Energy, performed an experiment to examine the impact of carbon dioxide levels on mental performance. They exposed three groups to different levels: 600 parts per million (ppm), 1,000 ppm, and 2,500 ppm. The higher levels used in the experiment can be found indoors, even in buildings with regulation-standard levels of ventilation. Levels in classrooms, where many people are confined in a relatively small space, can exceed 3,000 ppm.

The participants in the study were exposed to each concentration for 2.5 hours and then asked to perform a series of computer-based tests. The tests measured nine different performance factors, including breadth of approach and how well participants utilized information. At 1,000 ppm there was a small decrease in performance in six areas, while at 2,500 ppm, seven areas suffered and the effect was much bigger.

Article Continued Below

Co-author William Fisk noted that although the study was relatively small, the the impact was startling. “Our effect was so big, even with a small number of people, it was a very clear effect,” he said. He suggests that previous research my have missed the impact because the tests they used were too simple, such as adding columns of numbers or proofreading a piece of text. This study used a test known as Strategic Management Simulation, which measures reaction to given scenarios. Performance on the SMS has been linked to job level and income. The report concludes that there could be implications for education and the workplace, with further research needing to be done.

Show Me The Proof

Berkeley Lab: Elevated Indoor Carbon Dioxide Impairs Decision-Making Performance
Is CO2 an Indoor Pollutant? Direct Effects of Low-to-Moderate CO2 Concentrations on Human Decision-Making Performance