High CO2 levels in office 'may be sending you off to sleep mid-afternoon'
High levels of carbon dioxide in offices and classrooms could be affecting our concentration and decision-making abilities, researchers say.
The primary source of indoor carbon dioxide is humans. While typical outdoor concentrations are around 380 parts per million (ppm), indoor concentrations can go up to several thousand ppm.
According to the researchers, higher levels indoors are usually due to poor ventilation, often a result of the need to reduce a building's energy consumption.
Scientists from the State University of New York and the Lawrence Berkeley National Laboratory at the University of California found that carbon dioxide concentrations in office buildings normally don't exceed 1,000 ppm, except in meeting rooms, when groups of people gather for extended periods of time.
In classrooms, concentrations frequently exceed 1,000 ppm and occasionally exceed 3,000 ppm.
While these levels weren't found to be dangerous to health, they did significantly impair people's ability to think or make decisions.
The researchers say even they were surprised by the results, which are the first to make a link between high levels of carbon dioxide and a decline in work performance.
"In our field we have always had a dogma that carbon dioxide, at the levels we find in buildings, is just not important and doesn't have any direct impact on people," the Daily Mail quoted study co-author and Berkeley scientist William Fisk as saying.
"So these results, which were quite unambiguous, were surprising," Fisk said.
At carbon dioxide levels of 1,000 ppm, which is fairly typical level for an office, volunteers showed a dramatic decline in performance in six out of nine tests. It became significantly worse when the level rose to 2,500ppm.
"Previous studies have looked at 10,000 ppm and 20,000 ppm; that's the level at which scientists thought effects started," co-author Mark Mendell said.
"That's why these findings are so startling," he said.
Classrooms were found to have particularly high levels of carbon dioxide due to the volume of people, prompting fears that exam performance could be affected
Although their study only tested decision making and not learning, the researchers say it's possible that students in poorly ventilated classrooms - or rooms in which a large number of people are gathered to take a test - could also be at a disadvantage.
The study has been published in the journal Environmental Health Perspectives.