How is it not dangerous to breathe in the CO2 that we breathe out into our masks?

Question

I’ve heard a lot of anti-maskers use the argument that since we breathe out CO2, it will become trapped in the mask and is dangerous to breathe back in.

Obviously, this isn’t the case, because doctors wear their masks for hours and hours on end while doing surgeries. However, I am wondering, how does it work?

In: Biology

Answer 1

Forget the co2. If masks worked like that, no o2 would pass through and you wouldn’t be able to breathe at all.

Both o2 and co2 will flow freely through the mask, otherwise nobody could breathe with one on.