It's actually a hard problem. Think of CO2 like ping pong balls. If you have a cube of balls 100 * 100 * 100 you've got a million balls. Then mark 400 random

It's actually a hard problem. Think of CO2 like ping pong balls. If you have a cube of balls 100 * 100 * 100 you've got a million balls. Then mark 400 random balls. Then lets them all fall to the floor. Find the marked balls. That's what sifting though 400 parts per million looks like and c02 molecules are smaller than ping pong balls.