I love my sports dust mask. Of all the masks I have tried, it fits the best and is the easiest to put on or take off. I can also run the temples through the top of the ear loops which prevents them from falling off while I am exercising - hah - or leaning over a pond! But we all goofed on this idea. Because there are special vents for exhaust, your breath droplets are going right out of the mask, therefore NOT protecting other people from YOU.
I have come up with a fairly simple way to shut off the valves and present it here in a PDF instruction guide.
Please note, this is a DIY project. I am not a Doctor and it's just my idea. If you choose to try this, you are taking responsibility. Stay safe!!!