The next time you’re feeling sleepy at school or work, don’t blame that “afternoon slump” everyone talks about, blame the building you’re in!

That’s the gist of new research in the journal Environmental Health Perspectives. It shows that the carbon dioxide levels found in most crowded classrooms and offices are high enough to actually impair our ability to concentrate, make decisions, and even stay awake!

For those who don’t know: Carbon dioxide – or C-O-2 - is the waste gas that we all produce when we breathe out. It also occurs naturally from burning certain fuels – like wood or coal, and in small amounts, it’s not dangerous to inhale. In fact, it’s what gives the sodas we drink that “fizz”.

The problem is that as C-O-2 levels go up, it can become toxic. For example, if more than 10% of the air we breathe contains carbon dioxide, it can cause dizziness, headaches, vision loss, and unconsciousness!

The good news is that most buildings contain less than one percent of those toxic C-O-2 levels. But as the day goes on, all that air we breathe in and out causes C-O-2 levels to rise.  And the more people around us, the more C-O-2 we’re breathing.

In fact, this study found that a typical work meeting room contains three times the carbon dioxide that we’d normally inhale outdoors! That’s nowhere near enough to pose a health hazard.  But as this new study found, it’s enough to disrupt our focus and decision-making ability. It also explains why we tend to walk out of long meetings feeling sleepy, because we’ve just been sitting in a crowded room, breathing each other’s C-O-2!