Why do we not breathe back in the CO2 we just breathed out?

Question

We don’t breathe out with much force, and even if we did, we immediately inhale. So, how do we not just inhale what we just exhaled?

In: 14

Answer 1

The shortest answer is that gasses move around. You exhale, that dilutes in the atmosphere, then you breathe in nearly all fresh air.

There is some ‘dead’ air that leaves your lungs but doesn’t make it out your mouth or nose and is pulled in with your next breath. A baseline is around 150mL between nose, throat, and lungs. That may be around 30% of your total “breath”