Modifying a Mask to Protect Others During COVID-19

A very simple idea discussed with various people during streams to add a simple exhale filter layer to gas masks or respirators. The idea is that it protects other people from your germs as well as protecting you from others.
I am sure someone can come up with a much better idea than this.
This is done by simply sticking a tissue after the exhale valve to catch spittle leaving the mask.