From a New York Times article (May 24, 2020):
Dr. Perencevich believes that face shields should be the preferred personal protective equipment of everyone for the same reason health care workers use them. They protect the entire face, including the eyes, and prevent people from touching their faces or inadvertently exposing themselves to the coronavirus.
The debate over whether Americans should wear face masks to control coronavirus transmission has been settled. Governments and businesses now require or at least recommend them in many public settings. But as parts of the country reopen, some doctors want you to consider another layer of personal protective equipment in your daily life: clear plastic face shields.
When I take my walk, which currently is my only outing, I wear a face SHIELD for my personal protection against contracting Covid 19 from others.
I gave up on the face MASK because it is uncomfortable, especially when I am breathing heavily while walking rapidly up hills.
There isn’t much research supporting the self-protective use of face shields, but the video accompanying this article was enough for me; notice the aerosol-free area behind the face shield.
While walking, I breathe In deeply through my nose, and exhale through my mouth, using “pursed lips”, which aids in oxygen extraction by holding the alveolae open.
Exhaling through the mouth also clears the air behind the mask for subsequent nasal inhalation.
With nasal inspiration, any SARS CoV-2 aerosol particles would be deposited in the nasal passages, Which are that much farther away from your vulnerable lung.
It isn’t perfect. For one thing, it wouldn’t protect you much if someone coughed at you from the side or behind. I often hold my breath reflexes when I hear someone cough, or when I pass closely (even 6ft.) to someone.
The face shield holds promise for protecting you from viral infection, including the “flu”.