How does the lungs know which is O2 and CO2? We breathe a ton of different gasses daily but what happens to the other gases other than O2 and CO2 when inhaled?

Question

How does the lungs know which is O2 and CO2? We breathe a ton of different gasses daily but what happens to the other gases other than O2 and CO2 when inhaled?

In: 729

Answer 1

Some good explanation here already, but the real oversimplified ELI5 version is that it’s the same as throwing some nails and some wood chips in a fire and asking how the fire knows which one to burn. It doesn’t, but the flammable stuff you put in the fire burns and the other stuff doesn’t.