Uhhh I can name a few masks that help
Gas masks - stops toxins from reaching you
Plague masks - they have flowers in them to stop the stench and they stop contact
Builder face mask - to stop the particles from reaching your lungs, they will harm you if not, kill you
Respirator / dust masks - to stop poison and or paint coming into your lungs
There I just wasted 5 minutes of my time to prove the use of masks