It's been discussed on the news and by others on this forum on the other thread. These only stop water particles that carry the virus. The virus can still pass through on smaller particles as you continue to breath through a mask. Some say 30 minutes max for these dust masks. Also these are not air tight and air can come in through the sides or gaps.

These are dust masks, not bio masks. About as good as gun background checks keeping guns away from potential criminals. False sense of security.