The next time you start to doze off in a meeting at work, it's not that your boss is boring or that you're not interested in the topic. OK, maybe it is. But you don't have to admit that anymore, because now you've got a scientific excuse for being groggy: Too many people are breathing.

In what many office workers might consider the greatest scientific discovery since the invention of the coffee break, researchers published a study showing that when you get too many people in too small a room, the accumulation of carbon dioxide created from all the breathing can reduce concentration levels and hamper decision-making ability.

A carbon dioxide rate of 1,000 parts per million (ppm) is considered the base line for good ventilation. Researchers at the State University of New York and University of California found that in enclosed meeting rooms, the rate can climb as high as 2,500 ppm. In follow-up tests, volunteers who took computerized tests at 1,000 ppm and 2,500 ppm performed slower and less accurately at the higher level.

The results don't surprise Dan Tranter, supervisor of the Minnesota Department of Health's indoor air quality unit.

"Poor ventilation can have a big impact on concentration and individual performance," he said. "High levels of carbon dioxide often are indicators of high levels of other contaminants."

The researchers theorized that part of the problem might be that offices are turning down their ventilation systems to save money on energy, and Tranter agreed that a solution might be as simple as cranking up the fans. All things considered, that does seem a lot easier than asking people not to exhale.