Obviously unless you have a full positive pressure, over-the-head external (or HEPA filtered) air source helmet/mask and suit, you can't stop 100% of any airborne particles or droplets.
But a wearing your seatbelt isn't a 100% guarantee that you will be unhurt in any collision.
No typical safety equipment is 100% effective.
But we use it because it provides a level of protection that outweighs the hassle or cost of using it.
Wearing a mask is a no-brainer in my opinion if you have access to one, use it properly, and aren't denying it to someone who is at a greater risk than you.
And if you are taking care of someone at high risk, you owe it to them to protect yourself from catching it or potentially spreading it should you turn out to be positive but asymptomatic. In fact, assuming asymptomatic people are responsible for a lot of the spread, doesn't everyone owe it to everyone else to wear a mask for the protection of everyone else?
The only reason not to wear a mask when you're around others out in the world right now is if there is a shortage of masks. Which obviously there is.
So even well designed home-brew masks make sense right now. Again, use them properly, which means assuming the outside surfaces will end up contaminated. But why not do what you can to reduce the spread from you to others as well as from others to you?
The idea that this cannot be spread by droplets expelled into the air seems preposterous to me. It may be a matter of degree, of course, but if someone sneezes or coughs in my direction, I'm going to wish they had a mask of some sort on.
And what if you or someone else coughs or sneezes in the vicinity of products that someone else is about to pick up at the store? If I'm wearing even a bandana, and I cough in the store, wouldn't you feel a bit better than if I had no covering at all, and just let it fly?
Did any of you see the episode of mythbusters where they tested how far droplets fly when you sneeze? It was both hilarious and informative. Six feet? You wish!
