To tell you the truth, I don't know the reason of following arguments.

For not only the prevention of COVID-19 infection but also influenza, the following article are often heard.

(1)Face masks are effective to prevent expanding from infection, when we are carriers(infected patient).

However,

(2)Face masks are ineffective to prevent infection from other carriers, when we are non-carriers.

I have often read the articles.

I really don't know

"How this unsymmetrical logic can be established ? "

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According to COVID-19 at this time, it is clear that "rich contacts" is related to the possibilities of the infection.

This means that the infections are depending on the mount of virus from the carriers.

So I think that the infections are confirmed by many virus from carriers

and few virus is going to be destroyed by immune system of our body.

So I think that the face masks are quite competent to prevent infection.

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I read that "virus adhere to face masks infect us" before.

I can agree with the story, however, this argrument should be applicable for clothes and every things around us.

It is a typical misleading to confuse the story with "Face masks are ineffective to prevent infection from other carriers".

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Now I am masking instinctively.

If possible, I want to decide whether I should mask or not logically

So I except to hear presentations by experts of thie field.

By the way, you don't explain about the story of "size" about virus, bacteria and spray of spit, except for the relationship with unsymmetrical viewpoints.