To add to the sibling comment, which is correct, I actually created a model [1] that showed that any impedance leads to the air behind a mask eventually stabili

To add to the sibling comment, which is correct, I actually created a model [1] that showed that any impedance leads to the air behind a mask eventually stabilizing at half oxygen and half carbon dioxide. This means that any mask will eventually lead to about the same carbon dioxide intake, even if they let air through quite freely. [1]: https://gavinhoward.com/2020/08/masks-and-carbon-dioxide/ https://gavinhoward.com/2020/08/masks-and-carbon-dioxide/