My youngest son asked me a question today. At first glance, it seemed to be a very simple question.
Do you breathe out the same amount of air that you breathe in?
I explained that the volume of individual breaths varies, but that my first thought was that average inhalation must be the same as average exhalation -- because if it wasn't you'd either end up with a vacuum or overinflated. Then I remembered that you actually absorb molecules from the air and return others in the process of respiration. I'm not sure that the quantity is measurable, but I'm not so sure that you exhale the same amount over the long haul as you inhale. So I told him that.
Why don't you blog about it and see what other people think.
He'll nag me if you don't comment. Facts would be nice, but we'll settle for opinions if that's all you've got.