For those of you who think that masks are only for keeping others from getting your illness

[drmeow]

7. When I worked at a hospital

I had to be fitted for a mask. The mask does two things - it is sealed all around you face so air can only come through the mask and it filters the air. They test it spraying a fragrant sugar solution at you while you are wearing the mask. If you can smell it or taste sweetness, they change the size they are testing on you and retest you until you can neither smell nor taste anything. If smells can get through - you are not protected from airborne particles.

It does not appear as though the virus is contagious via airborne transmission. However, if your makeshift mask prevents you from touching your nose and mouth and reminds you not to touch your eyes, it will probably help.